Page 1

Focu s on Dev elop men t of Bra zilia n Min eral Sect or

SGB-CPRM

Brazil Geological Survey under the Spotlight

SGB-CPRM Programs: Program I Geological Geophysical Integration and Predictive Prospectivity Mapping of the Brazilian Shields

Program II Basic Geological Mapping

Program III Mineral Potential Assessment of the Brazilian Volcano-Sedimentary Sequences

Project Areas: Carajás Fe, Mn, Cu-Au, Ni, Au-PGE, PGE-Ni, Au-Mo-W-S, Cu-Zn, Sn.

Tapajós Au, Au-Cu, Sn, W

Quadrilátero Ferrífero Fe, Au, Mn, Sn, Au-U

Alta Floresta Au, Au-Cu, Zn-Pb-Cu-Au

Borborema (Seridó) W, Au, Fe, Fe-Ti, Cr, Cr-PGE, Cu, Pb-Zn

Program IV Crustal Evolution and Metallogeny of the Brazilian Mineral Provinces

Program V Thematic Projects

Nova Brasilândia Zn-Pb, Au

NW Ceará Cu, Pb-Zn, Mn

Gurupi Au


Brazil

South America There is a global consensus: Brazil is one of the world top players in the mining industry. The country covers a very large area (8.5 million km2), 43% of which with poten als for iron ore, precious and base metals, diamonds, bauxite, manganese, n, rare earths, graphite and other mineral commodi es. Brazil has low maturity despite of high fer lity due to its very low levels of investments in mineral explora on, offering therefore a significant poten al for new discoveries. The Geological Survey of Brazil (CPRM) provides the state of the art of the mineral poten al of the country, with focus on the main mineral provinces like Carajás, Iron Quadrangle and others. The studies presented in this document consolidate the knowledge accumulated during the last decades, by integra ng disciplines like geology, geochemistry, geophysics and metallogenesis. Their interpreta ons in progress for the most important mineral provinces of Brazil can result in great exploratory programs, leveraging the mineral explora on and adding value to the Brazilian mining sector.

Eduardo J. Ledsham President of CPRM - Geological Survey of Brazil

Produced by

DGM - Board of Geology and Mineral Resources José L.S. Andrio

- Director

Editors Noevaldo A. Teixeira (noevaldo.teixeira@cprm.gov.br) Marco T.N. Carvalho (marco.naves@cprm.gov.br)

Reviewers Joana T.R. Magalhães Mahyra F. Tedeschi Chris an M. Lacasse Julio M.M. Pinho Rafael B. Lima

Contributors Iago S.L. Costa, Loiane G.M. Rocha, Raphael T. Correa, Warley A. Pereira, Paulo H.M. Varão, Joseneusa B. Rodrigues, Marcelo d.S. Marinho

Aknowledgements ADIMB Vale S.A. Mineração Santa Elina Serabi Gold plc AngloGold Ashan 2ª Edição


TEIXEIRA, Noevaldo A., ed. T266b

Brazil : Geological Survey Under the Spotlight / Editores Noevaldo A Teixeira e Marco T. N. Carvalho. – Brasília : CPRM, 2017. 54 p.; il. color. Inclui Referências Bibliográficas

1. Geologia – Brasil. 2. Recursos Minerais – Brasil. 3. Serviço Geológico do Brasil. I. Carvalho, Marco T. N., ed. II. Título CDD 558.1

Indexes for systematic catalog 1.Geologia : Brasil 2.Recursos Minerais : Brasil 3.3. Serviço Geológico do Brasil

558.1 553.0981 352.081

2017


Under The Spotlight

NW Ceará

Carajás Nova Brasilândia

Seridó

Tapajós Juruena-Teles Pires

Quadrilátero Ferrífero

L E G E N D 0

500km

Intracratonic Basins Mobile Belts Cratons

Highlights BRAZIL by Neoproterozoic-to-Archean terrains, all with high potential for metals.

ü Brazil is a world key player in the mining sector

and will continue to be. All the efforts are being made by the Brazilian Government to bring back the attractiveness of the country, including major investments by the Geological Survey of Brazil (CPRM) to generate high quality geological, geophysical and geochemical data.

ü Compared with countries of similar geological

setting such as Australia and Canada, Brazil benefits from many less investments in mineral exploration, making its exploratory potential underestimated.

ü Most of the Brazilian cratonic areas are already

ü Brazil is one of the world leading producers of

covered by airborne magnetic and radiometric survey with 500-m line spacing. Semi-regional geochemical sampling and assessment already cover many parts of the main mineral provinces. Geological mapping at 1:100,000 scale, focusing on areas with greater mineral potential, is in progress. All the data are freely accessible from the online GeoSGB database (http://geosgb.cprm.gov.br/).

niobium, iron ore, vermiculite, bauxite, graphite and kaolin, as well as an important exporter of tin, nickel, magnesite, manganese, chromium, gold and dimension stones. ü Despite its large potential, Brazil continues to

import copper, sulfur, titanium, phosphate, diatomite and zinc, and also has a deep external dependence on coal, potassium and ETR. The window of opportunities is open for small-to world-class mines.

ü The geological endowments of Brazil are

similar to those of major ore producing countries such as Australia, Canada and South Africa. 43% of the continental area is covered

ü Gold and diamond productions are rising thanks

tonew discoveries and mining development.

i


ü Limited deep mineral exploration has been

Quadrilátero Ferrífero

carried out in Brazil, including in “mature” provinces as exemplified in the Quadrilátero Ferrífero. Less than 15 underground mines of gold, chromite, copper and zinc are currently in operation in Brazil, which corresponds to less than 4% of the total number of mines. There is an increasing potential for deep discoveries and mining development.

ü The Quadrilátero Ferrífero (QF) is one of the

most important mineral provinces in the world. First gold discovery dates from 1695, with continuous production since then (>50 MOz Au). ü Current known resources and reserves exceed

20 MOz. There are six gold mines in operation. The two major deposits are Morro Velho that produced 470 tons of gold between 1725 and 2003, and Cuiabá with 150 tons of gold in past production and reserves.

ü Archean and Paleoproterozoic greenstone

belts are widely distributed in Brazil, both in São Francisco, Amazon and São Luís cratons, with a clear potential for significant new discoveries, in particular for gold and sulfide nickel.

ü For indication, AngloGold Ashanti produced

421,000 Oz Au in 2015 in three mines (Cuiabá, Lamego and Córrego do Sítio) while Jaguar Mining produced 96,536 Oz from three other operations (Turmalina, Pilar and Roça Grande mines) in 2016.

ü The country has also a real potential for new

discoveries in geological formations derived from Earth´s mantle processes: carbonatites, IOCG, intraplate magmatic gold deposits, TZ diamonds and epithermal gold in anorogenic complexes.

ü There are currently 52 iron ore mines in

operation at QF, some in care-and-maintenance due the low commodity prices in 2016. More than 12 billion tons of iron ore have already been produced at QF, with grades above 50%.

ü Brazil has an important history of alluvial

diamond production. The current number of known outcrops of kimberlites, lamproites and related rockssums up to 1,344, with only one primary mine to date that produces high quality gemstones (Braúna Mine, in Bahia State).

ü The western portion of the QF, where the

Turmalina mine (Jaguar) is located, includes o c c u r re n c e s o f ko m at i i te f l o ws , fe l s i c pyroclastic rocks, BIF sulfide facies, and unusual clay epithermal alteration systems. A new discovery by Iamgold (São Sebastião) confirms the high potential for this underexplored portion of the QF.

ü The world-class discovery of the Zn-Cu

Aripuanã deposit opens a new exploratory frontier related to Paleoproterozoic continental rifts, particularly in northern Mato Grosso and Rondônia states. ü The probability of new Cu-Au discoveries in the

Carajás

Goiás Magmatic Arc is high. Recent understanding has emerged on the role of metamorphism and deformation in the origin of porphyry-style mineralization.

ü The Carajás Mineral Province (CMP) is among

the largest polymetallic mineral provinces in the world, the second largest for IOCG (Cu-Au).

ü The Neoproterozoic belts at the margin of the

ü The CMP iron ore deposits have the highest

cratons have characteristic tidal-flats and organic-rich lagoon sedimentary facies, which are still largely unexplored for Morro do Ouro type gold mineralization (Kinross, >20 MOz Au).

grades in the world with >65% Fe. Current resources and reserves are estimated >20 billion tons. Vale currently operates mines at the northern (N4 and N5) and southern (S11D) portions of the province.

ü The potentials are considered very high for Ni in

magmatic conduits, iron oxide-nickel-copper (IOCG and IONC) mineralization, and Zn-Cu-rich sediments related to the Amazonian intracratonic rifts.

ü There are four copper-gold mines currently in

operation at Carajás including Salobo (200,000 tpy, Vale), Sossego and Sequeirinho (100,000 tpy combined, Vale), and Antas North (Avanco Resources).

ii


ü The nickel produced at Carajás comes from the

ü About 700 tons of gold have already been

Onça-Puma laterite nickel operation, with production of 24,400 tons in 2015. Other important deposits are Vermelho, Jacaré, Jacarezinho and Mundial.

produced by artisanal prospectors (garimpeiros) from mostly alluvial formations. The economic potential of the area remains underestimated due to a limited scientific exploration that has been carried out until now.

ü Other mining operations at Carajás include the

ü The main deposits already determined at TGP

Azul and Buritirama manganese mines and small cassiterite operations at São Felix do Xingu.

are Tocantinzinho (3.9 MOz Au reserves and resources), São Jorge (1.58 MOz Au), Coringa (913 KOz Au), Palito (668 KOz Au) and Boa Vista (336 KOz Au).

ü Carajás is a polycyclic geological province with

several mineralizing periods leading to different types of deposits: Cu-Au-Zn, PGE-Ni reef, IOCG, IONC, Cu-(Au-Mo-W-Sn), Cu-AuMo-F, Fe, Mn, laterite nickel.

Juruena – Teles Pires

ü The most significant deposits in Carajás were

discovered from geochemical and magnetometric surveys. The discovery of even undetected magnetic IOCGs is considered also possible.

ü The Alta Floresta Mineral Province (AFMP)

extends from northern Mato Grosso State to Amazonas State. A 600 km long prolific gold trend gave rise to a past production of 300 t Au.

ü New discoveries of IOCG deposits are to be

ü Au-Cu occurrences, hosted in subvolcanic felsic

expected, particularly when more detailed works will be developed in the areas where the presence of BIF might possibly mask magnetic responses of the IOCG.

rocks and associated to propylitic and phyllic alterations, have been identified at AFMP without however having been adequately drilled for exploration.

ü The targeting of small-size, high-grade Cu-Au

ü Almost all the gold deposits in Brazil have

deposits, such as in progress by Avanco at Antas and Pedra Branca deposits, and by Tessarema Resources at Maravaia Project, represent an important development step for CMP.

been so far discovered by “garimpeiros” or by broad geochemical reconnaissance. Little scientific exploration has been carried out. Gold, gold-copper and polymetallic sulfide deposits have been discovered at AFMP, which are coeval with volcanic-plutonic rocks dated between 1.82-1.70 Ga. The main deposit is Aripuanã and consists of worldc l a s s Z n - P b - A g - C u - A u co n c e nt rate d at northern Mato Grosso State.

ü There are also possibilities for base metal

discoveries along lateral variations in BIFs. Possible syn-sedimentary faults with evidences of exhalative feeding have been found. ü The Cu-Au mineralizing corridors extend the

area of the Carajás basin mainly to the south into the Rio Maria Domain.

ü There are currently only one small gold mine

(Paraíba) in operation and one project under licensing (Aripuanã) in the whole AFMP.

Tapajós ü The gold mineralization of Tapajós Gold Province

Seridó

(TGP) has some characteristics similar to several other Au-Cu mineralized areas around the world.

ü The Seridó Mineral Province (SMP) has been

hosting tungsten mines since the 1940´s with some that are still in production, and more recently gold, iron ore, gemstones and kaolin mines.

ü The TPG is essentially a siliceous large igneous

province with a magmatic system covering an 2 area of 480,000km . The quartz-sulfide-gold veins there represent roots of mineralizing processes associated with the past activility of hundreds of calderas and other volcanic edifices. High and low sulfidations were both parts of the overall mineralizing process.

ü The SMP has over 700 skarn occurrences

containing W-Mo (Brejuí, Bodó, Bonito, Malhada Limpa and Quixadá mines), gold (Itajubatiba mine) and gold with associated W-Mo-Bi-Te (Bonfim mine).

iii


ü The main tungsten deposits are located at Brejuí

cratonic fragment, while dozens of other deposits are still being explored. Current resources for these main deposits are estimated to about 6.1 MOz Au. The only operation in the area is the Aurizona gold mine owned by Trek Mining.

(initially 11 Mt of WO3 - 5.5 Mt remaining at 0.51.0% WO3) and Bodó (9 Mt at 2% of WO3). ü The potential for base metals associated with the

skarns has yet to be explored, even with the presence of massive sulfide lenses associated to some of the tungsten mineralizations.

Northwest Ceará

ü The São Francisco deposit, in licensing process by

Crusader Resources, contains 1.61 Mt of proven and probable reserves and a total of 2.43 Mt in a l l - cate go r i e s re s o u rc e s ( htt p : / / w w w. crusaderresources.com/projects/borboremagold/, 19/02/2017).

ü The geology of northwestern Ceará State

comprises a metasedimentary sequence with potential for SEDEX-type deposits, formed on a passive continental margin between 800-750Ma and deformed during the Brasiliano/Pan-African Orogeny.

ü Mineral exploration at SMP has been very

limited until now, focusing mainly on tungsten. New opportunities for gold and base metals are being considered from their discovery in Mesoarchean volcano-sedimentary sequences.

ü A series of NE-SW shear zones, extending over

200km, hosts distinct deposits and mineral occurrences of copper, lead, zinc, manganese and iron. ü The three main Cu-Pb-Zn exploration targets

include Uruoca, Pedra Verde Mine and Serra de São José.

Gurupi

ü Geophysical anomalies indicate potential for

ü The São Luis cratonic fragment was isolated from

copper of undetermined mineralization, including underneath the Silurian sediments of the Parnaíba Basin.

the West Africa Craton and remained in South America after the opening of the Atlantic Ocean. ü The Chega Tudo and Igarapé de Areia formations

are therefore comparable to their African counterparts represented by the Ashanti Belt, Sefwi and Tarkwan Groups, which host giant ore deposits with a total endowment of about 125 MOz.

Nova Brasilândia ü The Nova Brasilândia Group in Rondônia State

(western Brazil) hosts recently discovered polymetallic sulfide mineralizations (Zn-Cu-PbAg-Au) that are associated to a meta-sedimentary sequence (Migrantinópolis Formation).

ü The Tentugal shear zone with its gold trend

extends for more than 100 km along strike and is interpreted to continue to the North beneath t h e C a m b r i a n - P h a n e rozo i c c o v e r. T h e similarities between the Tentugal shear zone and Birimian mineralizations are particularly evident in terms of host rocks, mineralizing processes and tectonic control.

ü Geophysical data suggests that this sequence is

continuous for at least 500 km in the E-W direction, with its eastern and western portions covered by Cretaceous sediments and Quaternary sediments, respectively.

ü New exploration targets have been highlighted

by the Geological Survey of Brazil (CPRM) on its predictive prospectivity map of Gurupi Belt, which are associated to both first- and secondorder structures and their extension underneath the sedimentary cover. All the relevant geological, geophysical and geochemical informations are freely accessible from the online GeoSGB database (http://geosgb. cprm.gov.br/).

ü The polymetallic occurrences are 5-40 m thick

and 0.3-3 km long, and characterized by massive and disseminated sulfide zones (gossans at surface) that are strongly oxidized, iron oxide veinlets and stockworks, siliceous breccia and quartz veins. ü Most of the sulfide-rich zones occur along a >50 km

long magnetic lineament which was interpreted as a sinistral transpressional fault. Other parallel lineaments were observed and represent a potential for future exploration programs.

ü Four main deposits with already defined

resources are known at Gurupi Belt and São Luís

iv


Geotectonic Setting of Brazilian Mineral Deposits Noevaldo A. Teixeira, Leonardo B.L. Lopes, Anderson D.R. da Silva

Brazil is a major world producer of mineral commodi es such as Fe, Nb, Au, Cu, Zn, Mn, diamonds, Sn, Cr, Ta, and P2O5, which are mainly derived from the two world-class mineral provinces of Carajás (State of Pará) and Quadrilátero Ferrífero (State of Minas Gerais) (Figure 01). The main deposits and tectonic se ngs for each region of interest in Brazil are discussed below. The eastern part of the Brazilian territory is mainly formed of

reconstruc on of evolu onary models involving island and/or con nental arcs derived from subduc on processes remains fragile and lacks of complete field evidences (e.g. oceanic crust, ophiolites, sutures, paired metamorphic belts and tectonic vergence). Furthermore, there is a predominance of extensional structures and bimodal magma sm that are be er explained by underpla ng processes induced by mantle plumes (e.g. Uatumã, Parauari). The Brazilian metallogenic se ng results from two geodynamic processes including subduc on of the oceanic lithosphere and interac on of a mantle plume head with a con nental lithospheric keel. The

Carajás Province

Ty p e s o f D e p o s i t s

Algoma type (Fe) Superior Lake type (Fe) Rapitan type (Fe-Mn) Oolitic ironstone (Fe) Carbonatite-alkaline complexes (Ba-P-Nb-REE-Ti-U) Layered mafic-ultramafic complexes (Cr-Ni-PGE-Ti-V) Lode (Au-Cu-Pb-Zn) Orogenic (Au) Paleoplacer (Au-U) Porphyry (Cu-Au-Mo) Intrusion Related (Au-Cu-Mo-U) Epithermal (Au-Cu-Pb-Zn) Greisen (Sn-REE) VHMS (Pb-Zn-Cu-Au) IOCG (Cu, Au) Skarn (Au-W) SEDEX (Pb-Zn-Ag-Cu-Ba) MVT Irish Type (Pb-Zn)

Borborema

Maroni-Itacaiúnas Mobile Belt

. .

Au, W, Fe-Ti, P-U

Sergipano Belt

2.20-1.95 Ga

0.85-0.60 Ga

Cr, Ni

Au, Mn, Cr

.

Au-S-W Iron Quadrangle

Uatumã FLIP

Fe,Mn,Cu-Au, PGE-NI, Sn

2.05 - 1.87 Ga

Araguaia Belt Au-Cu, Ni, Pb Zn, Zn-Cu, P

3.1 Ga

Fe, Mn, Au

Au

LEGEND

Phanerozoic cover Mobile belts (0.7-1.0 ga) Proterozoic sedimentary cover Cratons

.

Au, Mn

S.Francisco Craton

Amazonas Craton

Sedimentary deposits (Ba-Cu-Mn-P) Evaporites (K-Gypsum-Salt) Secondary Deposits (REE-Ti-Zr) Supergenic (Bauxite-Kaolin-Au-Mn-Ni) Primary Diamond Deposits Secondary Diamond Deposits

Paraguai Belt Paraná Craton

Brasília Belt

0.9 Ga Ma

Figure 01 - Loca on map of the main mineral deposits in Brazil.

Archean and Paleoprotherozoic cratonic nuclei that are surrounded by Neoproterozoic mobile belts (Figure 02). These old terrains are covered by Phanerozoic intracratonic basins making up an important part of the Gondwana paleocon nent (Cordani et al., 2000). Most of these belts are orogenic and built up by ri ing, ocean floor forma on, subduc on-related volcanic arcs, and collision processes (e.g. Brasília, Araguaia belts, Borborema Province). The Amazonian region (Central Brazil and Guianas shields) has a different setup where the cratonic nuclei are progressively surrounded by younger terrains, and for which the geotectonic se ng is s ll poorly understood due to the scarcity of Neoproterozoic records. The

Figure 02 - Disrup on of the con nental crust in the central region of Brazil at the beginning of the orogenic belts forma on. The disrup on was caused by plume impact and ocean floor forma on, with mantle dynamics having a major influence on the forma on of Neoproterozoic mineral deposits.

eastern por on of Brazil (São Francisco Craton) was surrounded by Neoproterozoic Brazilian orogenies that were built up by the subduc on of the oceanic crust. This region hosts mineral deposits such as sedimentary exhala ve (SEDEX), porphyry copper, podiform chromite, volcanogenic massive sulfides (VMS), and orogenic gold. The origin of these deposits is linked to asthenospheric fer liza on caused by dehydra on of the subduc ng slab, with the release and interac on of fluids with pelagic

1


sediments. At the base of the Archean Amazonian Craton, i.e. subcon nental lithospheric mantle (SCLM), intense magma sm occurred during plumerelated ri ing and extensional tectonics, without however reaching an open-ocean stage. In the Carajás Mineral Province located in the Amazon Craton, deposits of iron oxide copper-gold (IOCG) and n (Sn), banded iron forma ons (BIFs), and NiPGE (pla nium group elements) reef deposits were predominantly formed in associa on with underpla ng-driven tholeii c magma sm. Strong interac on of mantle-derived hydrothermal fluids and intense magma produc on due to thermal instabili es from a probable mantle plume, seem to have played a major role at the base of the Amazonian Craton (Teixeira et. al., 2009).

IOCG deposits such as Salobo, Alemão, and Sequeirinho, with total resources of the order of 2500 Mt at 1% Cu and 0.5 g/t Au (Teixeira et al., 2010). (3) The re-melted hydrothermal underpla ng stage at ca. 1.8 Ga, producing Cu-(Au-Mo-W-Sn) greisen (Breves deposit) and Cu-Au-Mo-F vein deposits (Gameleira deposit) associated with A-type granites (Teixeira et. al., 2009). The central por on of the Amazonian Craton, especially the Juruena and Tapajós provinces, encompasses extensive areas of alluvial and primary gold deposits - e.g. Tocan zinho with 49 Mt at 1.25 g/t Au, Juruena with 1.3 Mt at 5.6 g/t Au, Palito with 2.1 Mt at 5.85 g/t Au and 0.27% Cu, X1 with 8.5 Mt at 1.35 g/t Au and 4.6 g/t Au, Batalha, Paraíba, etc. The primary mineraliza on occurs mainly in granitehosted quartz veins and resulted from magma c fluid interac on causing phyllic altera on in the host rocks. They were classified more recently by authors as porphyry and epithermal systems, gene cally linked to subduc on-related hydrothermal systems (Juliani et al., 2014; Assis et al., 2015). We consider that the major gold deposits in these two regions are associated with intraplate bimodal igneous assemblages (Uatumã-Parauari, Teles Pires LIPs). The subvolcanic- and volcanic gold mineraliza ons are related to intraplate magma sm (plumerelated?) at the base of the SCLM (Amazon Craton). The Araí, Chapada Diaman na and Espinhaço groups in the São Francisco Craton were all deposited in an intracon nental ri during the Statherian period and host Sn deposits associated

Plume-Related Ore Deposits (Figure 03) The Carajás ri (ca. 2.7 Ga) was formed along the edge of an Archean subcon nental lithosphere keel (Amazonian Craton). Three main ore-forming stages are recognized in Carajás : (1) The plume stage (or decompression mel ng stage) at ca. 2.7 Ga, crea ng supergiant exhala ve sedimentary biochemical iron deposits (Carajás Forma on with a total of 18 billion tons at 60-67% Fe), exhala ve Cu-Au-Zn (Pojuca deposit) related to volcano-sedimentary sequences and A-type granite intrusion (ca. 2.7 Ga), and finally minor Ni-PGE reef deposits in tholeii c maficultramafic layered intrusions (Luanga deposit); (2) The fluid-metasoma zed mantle stage at ca. 2.5 Ga, concentrated along deep transtensional faults, with Au

Di

Au-Cu-Zn

Zn-Pb-Cu-Au

2,03 Ga

Au

2,03 Ga

Au

Fe-Mn-Au-Cu-Ni

TTG 3.30 Ga Underplate Metassome 70-90 km

Cr-Ni

2,70 Ga Ti, P, CI, CO2, ETR U, K, Na, Zr, Ca, Ba, Cu, Nb, Ni, Co, EGP, Fe, SIE, Alto Redox

P-Ti

Mn-Au-Cr

2.20 Ga

750 Ma

Metassome 120 - 200 km

280 Ma 90 Ma

Plumes

1.8 Ga 2.5 Ga 2.7 Ga

Astenosphere

Figure 03 - Schema c sec on across the Amazon Craton showing the distribu on of thermal anomalies (adiaba c melts or plumes) and the major paths for magmas and hydrothermal fluids. Some units were represented without deforma on effect.

2


carats from Douradinho, Santo Inácio, and Paranaíba, this making the diamond occurrence from the Triângulo Mineiro in the State of Minas Gerais (Coromandel, Alto Paranaíba) a new objec ve for explora on.

with greisens. In addi on, Au in veins cu ng dalflats and organic lagoon sedimentary facies were also found. Nonetheless, the Mesoproterozoic ri s in the northern por on of the Mato Grosso and Rondônia states host the greatest poten al for the discovery of new Pb-Zn-Cu SEDEX and VMS, like the world-class Aripuanã deposit, with 34 Mt at 4.27% Zn, 1.50% Pb, 0.29% Cu, 0.30 g/t Au and 37.39 g/t Ag (Votoran m Metais, 2011) and the Nova Brasilândia deposit, both being explored.

Subduc on-Related Ore Deposits (Figure 04) In the central por on of Brazil, Cu-Au deposits (Chapada region) occur in a Neoproterozoic subduc on-related magma c arc within the Brasília Orogenic Belt. These porphyry Cu-Au deposits, with 420.94 Mt at 0.29% Cu and 479.84 Mt at 0.25 g/t Au (Oliveira et al., 2016), were metamorphosed to the amphibolite facies and strongly folded. Brazil has favorable geological environments for volcanogenic deposits linked to volcanic ri s and paleo-volcanic arcs - e.g. Palmeirópolis, Bom Jardim, Vale do Ribeira, Salobro, Cabaçal. Behind the Brasilia Arc, in the opposite passive con nental margin, the metasedimentary sequence is thrusted over the edge of the São Francisco Craton. This sequence hosts Morro do Ouro Au deposit, Vazante Zn deposit and Morro Agudo Pb-Zn deposit. Morro do Ouro is a world-class gold deposit (600 t) that was possibly formed by biological accumula on of gold in a backreef environment before being remobilized by metamorphic fluids during thrus ng. Vazante and Morro Agudo deposits, with 18.3 Mt at 5.08% Zn and 1.75% Pb (Neves, 2011), were formed in an exhala ve se ng controlled by faults and diagenesis of a back-reef facies, respec vely. Both deposits are hosted in Neoprotherozoic carbonate

The presence of extensive translithospheric fault zones throughout the Brazilian Shield favored the intrusion, during the Cretaceous period, of several alkaline bodies - e.g. Poxoréu, Iporá, Alto Paranaíba, Serra do Mar, Caja , Jacupiranga, Catalão, Araxá some of them alkali-ultramafic and carbona tes hos ng supergiant Nb and large P2O5 deposits originated from lateri c weathering. Brazilian kimberlites occur mostly along pericratonic mobile belts with thinned or metasoma zed lithospheric keel. However, there are kimberlites in the São Francisco Craton where it was possible to infer, via deep seismic and thermobarometry of mantle xenocrysts, a depleted harzburgi c keel, >150 km thick, as in the case of kimberlites of the Nordes na region, State of Bahia (Braúna 3, the first kimberlitehosted diamond mine in Brazil). In the Amazonian Craton, mineralized kimberlites are found both in the depleted harzburgi c keel (State of Rondônia) and in mobile belts without lithospheric root. Un l now there is no robust scien fic explaina on for the source of several tens of alluvial diamonds over 100

Cu-Au

Ni-Cu Au 3 2 3.0 Ga

Zn-Cu

Al

Ni 4

5

6

P-Nb Di Cr Au Zn

7

8

10 9

Au-U Pb-Cu Pb-Zn Au Au Fe-Mn Au-Di Mg UPb-Zn Cr Au Cr Cu Di 11 12 3,4Ga

1 900-800 Ma

13 2.4 Ga

14 15 16

17 18

21 20 19 2,9 Ga

22

Fe

23 24

2,6 Ga

1 - Chapada, 2 - Crixás, 3 – Palmeirópolis, 4 - Barro Alto-Niquelândia, 5 - Americano do Brasil, 6 - Morro do Ouro, 7 - Moro Agudo, 8 - Vazante, 9 - Catalão, 10 - Alto Paranaíba, 11 - Januária, 12 - Quadrilátero-Ferrífero, 13 - Rio das Velhas, 14 - Espinhaço, 15 - Brumado, 16 - Lagoa Real-, 17 - Redenção, 18 - Medrado, 19 - Campo Formoso, 20 - Jacobina, 21 - Novo Mundo, 22 - Caraíba, 23 - F. Brasileiro, 24 - Nordes na. Figure 04 - Schema c sec on across the São Francisco Craton showing the distribu on of thermal anomalies (adiaba c melts or plumes) and the major paths for magmas and hydrothermal fluids. Unlike for the Amazon Craton, the mineralizing processes resulted from the interac on between the subduc ng oceanic slab and asthenospheric wedge, with the release of hydrothermal fluids.

3


rocks that were deformed during the Brasiliano Orogeny. In the northeast region of Brazil, the end of this orogeny (Seridó foreland basin) was marked by the emplacement of large grani c plutons with Au and W mineraliza ons. This magma sm was generated by delamina on of the lithospheric mantle, producing high heat flow by the invasion of asthenospheric material into the base of the con nental crust, and genera ng W and Au mineraliza ons (Ganade et al., 2013).

deposits - e.g. Crixás, Itapicuru, Cipoeiro, Aurizona, Chega Tudo, Amapari, Salamangoni, Volta Grande that lay on terranes of the Amazonian and São Francisco cratons. Brazil has also a significant number of diversified mafic-ultramafic bodies formed by plumes or mantellic adiaba c fusion occurring in a subduc on context. The mafic-ultramafic complexes are distributed infive main geotectonic se ngs: (1) TTG terranes and greenstone belts; (2) Intracratonic granuli c belts and roots of orogenic belts; (3) Ensialic ri s; (4) Subduc on zones in Neoproterozoic orogenic belts; and (5) Intracratonic basins. The most significant associated deposits are: (a) Ni-CuPGE deposits in reefs of intracratonic layered complexes (e.g. Luanga); (b) Ni-Cu deposits in Archean koma ite lava channels (e.g. Fortaleza de Minas); (c) Dissemina ons in magma c conduits controlled by translithospheric fault - e.g. Limoeiro and Caraíba with a total of 42 Mt at 1.82 % Cu (Dardenne and Schobbenhaus, 2001); (d) Synorogenic hydrated magmachamber (e.g. Americano do Brasil); (e) Dissemina ons in differen ated magmachamber (e.g. Mirabela); (f) Podiform chromite deposits in residual harzburgites (e.g. Morro Feio, Qua puru); (g) Stra form chromi te in cumulate at the bo om of layered complexes (e.g. Bacuri); (h) Fe-Ti-V-PGE deposits in magne te-rich layers between gabbro and piroxenite (e.g. Maracás); and (i) Lateri c nickel (e.g. Niquelândia, Barro Alto, Vermelho, Onça-Puma).

Ore Deposits Related to both Plume and Subduc on (Figure 05) It is possible that during the evolu on of TTG (tonalite-trondhjemite-granodiorite) greenstone belts, subduc ons and plumes have acted on a conjugate manner (Arnt and Nisbet, 1982). Brazil has a significant extension of these belts including for example the Archean Rio das Velhas greenstone belt (Iron Quadrangle), which comprises thick piles of metakoma ites, basal c flows, felsic metavulcanics, BIF and metavolcanoclas cs. Its gold deposits such as Morro Velho, Cuiabá and São Bento, with respec vely >470 t Au, >180 t Au and >80 t Au (Abreu et al. 1988), are hosted in BIFs that were sulfurized by metamorphic fluids during regional deforma on and low-grade metamorphism (greenschist facies). The giant iron ore deposits of the Minas Group occur in exhala ve chemical sediments that were deposited on TTG greenstone belts substratum (bedrock) in a context of passive con nental margin. Numerous other Archean and Paleoproterozoic greenstone belts in Brazil contain orogenic gold Pb-Zn Cu Cu 1 2 3

Mn

U-Pb

Cr-PGE 4

Au 6

5

Li-Ta pegma tes Fe -Ti W Au Fe Au 8 9 7

Au

Fe -Ti

10

610-650 Ma 2.2 Ga

2.2 Ga 2.7-3.0 Ga

1 - Martinopole, 2 - Pedra Verde, 3 - Jaibaras, 4 - Itataia, 5 - Tróia, 6 - São Fernando, 7 - Saquinho, 8 -Brejuí, 9 - São Francisco, 10 - Itapetim.

Modified from Araújo et al., (2013)

Figure 05 - Schema c sec on of the NE region in Brazil showing the mechanical erosion derived from delamina on of the lithospheric mantle. High heat flow produced huge felsic plutonism a er con nental collision of the Neoproterozoic Brazilian fold belt.

4


References ABREU, A.S.; DINIZ H.B.; PRADO, M. G.B.; SANTOS, S.P., 1988. A mina de ouro de São Bento, Santa Bárbara, Minas Gerais. In: SCHOBBENHAUS, C.; COELHO, C.E.S. (coord.). Principais Depósitos Minerais do Brasil. Brasília: DNPM, v. III, p. 393-411.

NEVES, L.P., 2011. Caracterís cas descri vas e gené cas do depósito de Zn-Pb Morro Agudo, Grupo Vazante.89 f., il. Dissertação (Mestrado em Geologia) Universidade de Brasília, Brasília, 2011.

ASSIS, R.R., 2015. Depósitos auríferos associados ao magma smo félsico da Província de Alta Floresta (MT), Craton Amazônico: Litogeoquímica, idade das mineralizações e fonte dos fluidos. 2015. 363 p. Tese (Doutorado) -- Ins tuto de Geociências, Universidade de Campinas, Campinas.

OLIVEIRA, C.G., OLIVEIRA, F.B., DELLA GIUSTINA, M.E.S., MARQUES, G. C., DANTAS, E.L., PIMENTEL, M.M., BUHN, B.M., 2016. The Chapada Cu-Au deposit, Mara Rosa magma c arc, Central Brazil: Constraints on the metallogenesis of a Neoproterozoic large porphyry-type deposit. Ore Geology Reviews, v. 72, Part 1, p.1-21.

ARNDT, N.T., NISBET, E.G., 1982. Koma ites. London: George Allen & Unwin, 526 p.

TEIXEIRA, J.B.G., LINDENMAYER, Z.G., SILVA, M.G., 2010. Depósitos de Óxidos de Ferro-Cobre-Ouro de Carajás. In: BRITO, R.S.C., SILVA, M.G., KUYUMIJIAN, R.M. (org). Modelos de depósitos de cobre no Brasil e sua resposta ao intemperismo. Brasília: CPRM, p. 15-48.

BRITO NEVES, B.B., FUCK, R.A., PIMENTEL, M.M., 2014. The Brasiliano collage in South America: a review. São Paulo, Brazilian Journal of Geology, v. 44, n. 3, p. 493-518. COMPANHIA VALE DO RIO DOCE. Carajas Iron Ore Mine, Brazil. Disponível em: www.mining-technology.com/projects/carajas Acesso em: 13 fev. 2017.

TEIXEIRA, N.A., FREITAS-SILVA, F.H., CORRÊA, C.R.A., ROSA, W.D., OLIVEIRA, J.K.M. DE, ROSENDO, O.S.C., PINHEIRO, JR. V., 2009. Evolução geológica e mineralizações primárias da Província Mineral de Carajás. III Simp. Bras. Metalogenia, Gramado, RS.

CORDANI, U.G., MILANI, E.J., THOMAZ FILHO, A., CAMPOS, D.A., 2000. Tectonic Evolu on of South America. 1ed. Rio de Janeiro: 31 Interna onal Geological Congress, v. único, p. 750-850.

VOTORANTIM METAIS. Aripuanã. Disponível em: <h p://www.vmetais. com.br/en-US/Negocios/ExploracaoMineral/PrincipaisProjetos/Pages/ Aripuana.aspx>. Acesso em: 13 fev. 2017.

DARDENNE, M.A., SCHOBBENHAUS, C., 2001. Metalogênese do Brasil. Brasília: UnB: CPRM, p. 114-115.

PIRAJNO, F., SANTOSH, M., 2015. Mantle plumes, supercon nents, intracon nental ri ing mineral systems. Precambrian Research, v. 259, p. 243-261.

GANADE DE ARAUJO, C.E., WEINBERG, R.F., CORDANI, U.G., 2013. Extruding the Borborema Province (NE-Brazil): a two-stage Neoproterozoic collision process. Terra Nova, v. 26, p. 1-12. JULIANI, C., ET AL., 2014. Metalogênese da Província Tapajós. In: DA SILVA, M.D.G., ET AL. (Org.), Metalogênese das províncias tectônicas brasileiras. Belo Horizonte: CPRM, p. 229-268.

5


Carajás Project Ulisses A.P. Costa, Desaix P.B. Silva, Jaime d.P.d.O. Barbosa, Junny K.M. de Oliveira, Rodolfo R. de Paulo, Raphael N. Araújo, Marcelo J. de Souza

The Carajás Project is being developed by the Geological Survey of Brazil (CPRM) as part of its programs “Geological Geophysical Integra on and Predic ve Prospec vity Mapping of the Brasilian Shields” (Program I) and “Mineral Poten al Assessment of the Brazilian Volcano-Sedimentary Sequences” (Program III). Considering the broad picture of the southeastern part of the Amazon Craton, the region is characterized by the presence of important polymetallic deposits that can be grouped into three main types according to their respec ve geotectonic se ng: (1) Archean TTG (tonalitetrondhjemite-granites) and greenstone belts hos ng orogenic gold deposits (e.g. Rio Maria Province); (2) Archean polymetallic subcon nental lithospheric mantle (SCLM) ri s hos ng world-class Fe, Cu-Au (IOCG), Ni (IONC and laterite), Au-PGE deposits (e.g. Carajás Mineral Province); and (3) Proterozoic epithermal and quartz veins gold deposits in the Tapajós area. The Carajás Mineral Province (CMP), formed from 2.76 to 2.55 Ga, is located in the eastern por on of the Amazon Craton, northern Brazil. It is considered as one of the world most important mining areas, including several world-class IOCG, nickel, PGE, iron ore and manganese deposits (Figure 01).

controls. Detailed mapping at 1:50,000 scale is being addi onally carried out for the volcano-sedimentary sequences that include the Aquiri unit. The large amount of geological data already published on the Carajás Mineral Province (CMP), together with recently acquired airborne radiometric (Figure 02), magne c (Figure 03) and gravity data, and remote sensing images, make the basis for the geophysicalgeological interpreta on maps in progress at the Geological Survey of Brazil (CPRM). All these data are freely accessible from its online GeoSGB database (h p://geosgb.cprm.gov.br/). The Mesoarchean Carajás basement assemblage consists of TTG granite-gneiss-migma te (Xingu Complex), mafic granulites (Xicrin Cateté orthogranulite), and greenstone belts (Sequeirinho, Selva and Rio Novo groups) that were dated at around 3.07-3.0 Ga (Pidgeon et al., 2000; Moreto et al., 2011; Silva, 2014). The Neoarchean Carajás basin comprises metavolcano-sedimentary units, dated at 2.76 Ga for the Itacaiúnas Supergroup (DOCEGEO, 1988), and that host the main Fe and Cu-Au deposits. The succession from base to top consists of bimodal mafic-felsic metavolcanic rocks, BIFs (hos ng giant iron ore deposits), metapyroclas c and metasedimentary rocks deposited in a marine ri environment (Gibbs et al., 1986). Metamorphism grade ranges from low greenschist to amphibolite facies. Coeval maficultramafic layered complexes (2.76 Ga, e.g. Luanga Complex; Machado et al., 1991) hos ng PGE-Ni deposits and syn-tectonic alkaline to sub-alkaline granites (2.76-2.70 Ga, e.g. Estrela and Gelado granites; Barbosa et al., 2001) are widespread in the Carajás Basin, as well as 2.65 Ga gabbroic dikes and

The Geological Survey of Brazil (CPRM) currently conducts three work programs dedicated to offer basic geological data and knowledge to investors, including: (1) Geophysical-geological integra on maps of ten 1:100,000 scale sheets; (2) Detailed mapping along the Cinzento Lineament aimed at establishing the main regional controls of the copper deposits located in this transcurrent system; (3) Detailed mapping of the Mn deposits to define their stra graphic and faciological

Jacareacanga

Maroni - Itacaiúnas Mobile Belt Au, Mn Volta Grande

Fe, Mn, Cu-Au, Au-PGE, Ni, Sn Carajás Ri

BIF

Uatamã Felsic LIP

Au, Ni

1.88 Ga

Au, Sn 2,76 Ga

Uatumã FLIP

Buri rama

Itacaiúnas SuperGroup

Cuiú-Cuiú Complex

Araguaia Orogen Cr-Ni

Rio Novo

2.70 Ga

2.15 Ga

Archean Primi ve Crust 2.00-1.88 Ga

Felsic Magma 2.10 Ga

Underplate Con nental lithospheric keel

Lithosphere

Lithosphere Astenosphere

Figure 01 - Geotectonic se ng of Carajás Basin interpreted either as a ri -related or strike-slip basin. It presents a typical sigmoid structure controlled by transcurrent shear zones (Araujo and Maia, 1991). The basement is composed of TTG greenstone belt. The eastern border of the Amazon Craton is delimited by the Bacajá fold belt (2.2 Ga) and obducted Neoproterozoic Araguaia ophiolite. The western limit was streched during a large Paleoproterozoic extensional event (Tapajós region).

6


K

eTh

eU

Figure 02 - Ternary gamma-spectrometry map (K, eU, eTh) of the Carajás project area and correla on with known geological features.

lt

au aF

rios

te Mis

t

aul

F less

nd

a McC Carapanã

Figure 03 - Magne c interpreta on of lineaments based on total magne c intensity (first deriva ve of magne c anomaly field).

7


sills. A Paleoproterozoic low-grade sedimentary sequence overlies the Itacaiúnas Supergroup and comprises fluvial to shallow marine sandstones and siltstones (Águas Claras Forma on; Nogueira et al., 1995) containing manganese deposits (Azul Mine). 0

Paleoproterozoic A-type granites (1.88 Ga; Dall'Agnol et al., 2005) outcrop throughout the Carajás region, as well as mafic and felsic NE and NW dikes (Figures 04, 05, 06 and 07).

0

52 30’W

0

51 30’W

0

50 30’W

49 30’W

Mn

Cu, Au Cu, Au Cu, Au Au, Cu

Ca

ra

Au

sF au

lt

0

6S

Fe

Mn

Sn

Au, Pt, Pd

Cu, Au

Cu, Au Fe

Parauapebas

Fe Mn

Ni

Sn

Cu, Au ault nã F

pa

Rio

Cara

Xin gu

Fe

Fe Cu

Fe

Ni

Cu, Au 0

6 30’S

Fe São Félix do Xingu

Canaã dos Carajás

Ni

Tucumã

Sn

Água Azul

Cu, Co Au

0

W, Sn

15

30km 0

7S

Cities Roads Rivers Railroad

Major lineaments Deposits Inactive mines Active mines (active)

TECTONOSTRATIGRAPHIC ASSEMBLAGES Mesoarchean TTG Suites Mafic granulites Greenstone belts TTG orthogneisses, migmatites and granitoids

Neoproterozoic Araguaia belt Paleoproterozoic (Orosirian) A-type anorogenic intrusions Rift basin (bimodal volcanic rocks) Rift basin (sedimentary rocks) Foreland basin

Paleoproterozoic (Rhyacian) Calc-Alkaline orogenic intrusions Intracratonic basin Neoarchean Alkaline to subalkaline intrusions Mafic-ultramafic layered intrusions Volcanosedimentary sequences

Figure 04 - Geological map of Carajás Mineral Province. Águas Claras Forma on

Pojuca

Pb-Pb (Z and WR): 1.88 Ga 1,87-2,0 Ga (DZ): 2,87 -3,05 Ga

2.76 Ga

U-Pb (Z): 2,65-2,70 Ga

(DZ) 2.87-3.05 Ga

Granites

Rhyolite Black Shale BIF Carajás Fm U-Pb (Z): 2,76 ± 2 Ga IZ: 2,85 to 3,42 Ga

TTG-Greenstone

Figure 05 - Carajás deposi onal environment showing high variability due to the strong tectonic compartmenta on of the ri -related (or strike-slip) basin. Black shale Silstones, sandstones, conglomerates shales, breccias

Sandstone Águas Claras Forma on

Black shale,sandstones Breccias Red Siltites Dolomites

Mafic lavas, BIF, Tuffs, metapelites, andesites, turbidites.

Salobo, Pojuca, Igarapé-Bahia Groups

Águas Claras Forma on

Mn Shale Red Sandstone Conglomerates

Basaltic flows Rhyolite

Basaltic flows Black Shale

Grão Pará Group

Mod. from Teixeira et al., 2010

Mod. from Teixeira et al., 2010

Basaltic flows

Metapiroclastics Jaspilites Greenstone belts: Komatiites, basalts, BIF, piroclastic and sedimentary rocks

Xingu Complex (>2,86 Ga)

Figure 06 - Stratigraphic column of Central Carajás.

BIF Luanga, Luanga Sul Mafic-ultramafic complex Greenstone belts: Koma ites, basalts, BIF, piroclas c and sedimentary rocks

Figure 07 - Stratigraphic column of Serra Pelada.

8

Grão Pará Group (2,76 Ga)

Xingu Complex (>2,86 Ga)


New geochronological data obtained from detrital zircons shows that the Aquiri Unit has a maximum deposi onal age around 2.86 Ga (Figures 08 and 09). This age does not indicate however whether the metavolcano-sedimentary sequence of Aquiri Unit is part of the greenstone belt or is related to the Itacaiúnas Supergroup. The maximum deposi onal age of the Água Claras Forma on obtained from detrital zircons is 3.24 Ga (Figure 10), highligh ng the absence of Transamazonic zircon ages.

Despite the mineral importance of the area its basic geological and geochronological knowledge is poor. The deposi onal environment of Carajás is highly variable due to the strong tectonic compartmenta on of the ri -related (or strike-slip) basin. There is no single stra graphic column that can apply to the en re Carajás region. In addi on the stra graphic units of Salobo, Igarápé Bahia, and Pojuca were only defined from drill hole observa ons due to the absence of outcrops.

490000

470000

450000

9344000

9344000

B

STRATIGRAPHIC UNITS PALEOPROTEROZOIC

A-type granite

450

000

Gabbros

NEOARCHEAN

Metamafic rocks Sub-alkaline metagranites

Cateté Suite Pyroxenites, peridotites and gabbros l vgranites Undifferentiated

Metavolcano-sedimentary Sequences

Quartzites, schists and BIFs Metarenites, metapelites Quartzites Phyllites Schists and BIFs BIFs Phyllites and quartzites Metabasalts Salobo-Pojuca Formation (quartzites and metapelites) Parauapebas Formation (metabasalts)

Edileuza

932

9328000

Aquiri Group

Liberdade Group

800

56°W

52°W

0

48°W

2°N

2°N

BRASIL

AMAPÁ

2°S

2°S

AMAZONAS

MESOARCHEAN

PARÁ STATE

Basement assemblage

MARANHÃO

Vila Sassá Gneiss (orthogneisses and granulites) Nova Índia Gneiss (ortho and paragneisses) Xingu Complex (orthogneisses and migmatites)

6°S

BRASIL

6°S

Aquiri area

A TOCANTINS PI MATO GROSSO 56°W

52°W

490000

470000

48°W

Figure 8 - Aquiri geological map. The western por on of Carajás is only covered by maps of 1:250,000 scale. The Geological Survey of Brazil (CPRM) is currently developing a 1:50,000 scale mapping program of the volcano-sedimentary sequences in this region (North of São Feliz). Its interpreted results will help separa ng the greenstones belts from the western con nuity of the Itacauinas Supergroup, while more precisely defining the limits of the Carajás Basin.

Number

2941 10

5

10

8

6

3395 4

2

3100

Idade

3186

3503

3200 0 2700

12

Águas Claras Formation

3271

3093

Relative probability

Relative probability

15

3248

14

Aquiri Group

2868

Number

20

3500 207

Pb/

0 2500

3900

206

2900

3300

Idade

Pb (Ma)

207

Pb/

3700

206

Pb (Ma)

Figure 10 - Combined histogram and probability density diagram of detrital zircon U-Pb ages from the Águas Claras Forma on. The youngest peak of 3093 Ma indicates the maximum deposi onal age. Although three crystals with younger age have been iden fied, due to their small number they were not further considered in the interpreta on.

Figure 9 - Combined histogram and probability density diagram of detrital zircon U-Pb ages from quartzite of the Aquiri Group. The maximum deposi onal age is indicated by the youngest peak of 2868 Ma.

9


Three main mantle-related mineralizing events are recognized in the Carajás ri (Teixeira et al., 2009): (1) 2.76 Ga crustal extension related to plume or descompression of the astenospheric mantle, resul ng in basal c and rhyoli c flows and giant hydrobiogenic volcanic-exala ve iron deposits (e.g. N4, S11D), minor disseminated volcanogenic Cu-Zn deposits (e.g. Pojuca), tholeii c mafic-ultramafic layered intrusions (Onça-Puma, Jacaré, Jacarezinho) with PGE-Ni reefs (e.g. Luanga) and IOCG deposits (e.g. Sequeirinho-Pista; Moreto et al., 2015); (2) 2.61-2.55 Ga crustal extension with decompression of the metasoma zed mantle, and forma on of saturated- (O-H-C-S-Cl-rich), blind metasoma c mantellic alkaline rocks and IOCG deposits (e.g. Salobo, Alemão); (3) 1.88 Ga intrusion of A-type granites refle ng a huge mantle plume event that affected the whole central Amazonian Craton, producing in the Carajás Province Cu-(AuMo-W-Sn), greisens (e.g. Breves), Cu-Au-Mo-F intrusion-related deposit (e.g. Gameleira), manganese deposits and the unusual Au-PGM Serra Pelada deposit. The last two of these deposits were correlated to the lowermost unit of the Águas Claras Forma on (Figure 10). Grainger et al. (2008) and Teixeira et al. (2009) considered that the metallogeny of the CMP is petrologically related to SCLM dynamics in an ac ve ri se ng. Conjugate metamorphic, hydrothermal and magma c events, dated between 2.70-2.55 Ga, were found to be contemporaneous with the reac va on of extensive regional shear zones, and important contribu ng factors for the Carajás metallogene c evolu on (Figure 11).

Iron Forma on are interbedded with metabasalts of the Grão Pará Group as part of the Itacaiúnas Supergroup. Rocks of the Grão Pará Group are exposed along the northern and southern flanks of a synclinal structure (Carajás syncline) that includes a major shear zone (Carajás shear zone) along its axis. Vale is the largest mine operator at CMP and has recently launched the S11D project, the world's largest iron ore mine with a produc on capacity of 90 Mtpy. The total iron ore resources from all known deposits exceed 20 billion tons with grades over 65% Fe. The orebody thicknesses vary between 250-300 m. Jaspilites cons tute the proto-ore of CMP iron ore deposits, with weathering being at the origin of such a high enrichment. High-grade iron ore mineraliza ons (>65 % Fe) consist of both hard- and so ores. The hard ores are banded, massive and/or brecciated, and mainly composed of microplaty hema te. Compara vely the so ores are very porous, discon nuous and tabular, friable and banded. The basal contact of high-grade iron ores is defined by a hydrothermally altered basal c rock that is mainly composed of chlorite and microplaty hema te (Silva, 2009). The mineralizing process is considered as vulcanogenic, with the high-grade por on reflec ng the proximity of the exhala ve centers (Teixeira et al., 2009) (Figure 12). CMP is the second largest IOCG (Cu-Au) province in the world (Figure 13). The IOCG deposits do not show any stra graphic preference or lithological control. They occur in granites, metabasalts, metarhyolites and metasedimentary rocks. The level of deforma on of the host rocks varies greatly, from cataclas c- (e.g. mylonite at Salobo) to weakly deformed rocks, which nevertheless determine the style of the ore bodies. The more competent rocks

CMP has some of the largest high-grade iron ore deposits in the world. These deposits in the Carajás

Ni 1

Fe

Black Shale

2

Au-Mo-W-S Cu-Au-Mo-F 5 4

Cu-Zn Bacteria

3

BIF

Greywacke Compact Hema te N4, N5, ...S11D

IOCG

Águas Claras Na Sossego, Sequinho Cristalino

2.70 Ga U/Pb

Tholeii c Basalt

Gameleira

Granite 2.7 Ga

Salobo

Post-Ri Fase 7. Mn Sedimentary 8. Au-PGE Redox Sedimentary 4 and 5. Felsic Intrusion Related (1.80 Ga)

5. IOCG 9. PGE-Ni Reef

Reef

Manganês do Azul Fe K Ca

Mafic 2.7 Ga

Luanga

Serra Pelada Breves

Cordierite - Antofilite

Hema za on Silicifica on Carbonata on

Sin - Ri Fase (2.76 Ga) 1. IONC 2. Hydrobiogenic volcanic-exhala ve iron deposit 3. BIF host volcanogenic Cu-Zn

6

PGE-NI 9 Perido te Pyroxenite -Gabbro

Au-PGE 8

Bahia

Cu, Au, Mo, F

Jaspe

Mn 7

Layered mafic-ultramafic intrusion 2,76 Ga Wirth et all., 1986

Mod. from Teixeira et al., 2009

Figure 11 - Types of mineraliza on in the Carajás Mineral Province (CMP).The Carajás Archean ri hosts a 200x100 km2 giant ore system. The basin was filled with con nental tholeii c basalts and rhyolites followed by BIFs and vocanogenic sediments. The upper unit is mainly composed of sedimentary rocks. Three main mantle-related mineralizing processes were recognized in Carajás ri . They involve magma c ac vity, exhala ve solu ons and hydrothermal fluids that contributed to the different types of mineraliza on.

10


Foto credits Vale

Foto credits Vale

Figure 12 - Pit of the N-5 iron mine.

Figure 13 - Pit of the Sossego copper gold mine.

include more veins and breccias and less subs tu on. The Cu-Au Salobo mine has been in ac vity since 2012 and is one of Vale's most important opera ons. It is also the largest copper mine in Brazil with a produc on of 200,000 tpy of Cu concentrate. The IOCG deposit there is the most deformed of all comparable deposits in CMP. It has undergone Paleoproterozoic deforma on and metamorphism, which resulted in a strong structural control materialized by E-W duc le-bri le shear zones with high-angle fault bends and jogs (Figure 14 and 15).

S a l o b o d e p o s i t re p re s e nt s t h e ro o t o f a hydrothermal system. As part of this system, Alemão and Igarapé Bahia deposits are posi oned higher in the stra graphic sequence, as reflected by their lower-temperature mineral associa ons. Schistosity and mineral linea on are also observed in the deposits and were formed during the hydrothermal altera on process. They were interpreted as resul ng either from the final stage of the complex deforma on history of mineralized conduits (2.5 Ga), or from the effect of later orogenies (Tavares, 2015). Carajás IOCG deposits have stable isotope signatures reflec ng deeply formed and/or mantlederived magmas. The ore forming process involved aqueous hypersaline, acidic and oxidizing convec ve fluids, which interacted with cooler and less saline

Carajás IOCG deposits have strong calcic, iron and sodic hydrothermal altera ons. The forma on depth of the metal deposits is important to determine from these associated altera ons. The

Buritirama Serra do Buritirama Buriti Madeira

GT-46 Salobo Liberdade

Furnas

Paulo Afonso

Breves

Serra Pelada

Gameleira Igarapé Bahia

Serra da lua Nova Serra do Jacaré

Águas Claras Estrela

Castanha Sequeirinho Sossego Puma

Bacia do Rio Xingu

Formiga Luanga Serra Leste

Mina do Azul

Igarapé Antônio Vicente

São Felix

Serra do Sereno

Carapanã

GT-34

Bacaba

Cristalino Visconde Brilasa Serra do Rabo Vermelho

Onça

Setor Biquinha

Fafá Alto do Rio Branco Sapucaia

Serra do Mocambo

Boa Esperança

Ourilândia do Norte

Bom Jardim

Mines

Mineral Deposits

Main structures

Figure 14 - Tectonic controls of IOCG mineralizations with the Carajás sigmoid structure in the central part of the figure. The extrapolated Cu-Au mineralizing corridor extends the Carajás Basin area mainly to the south into the Rio Maria Domain.

11


NE

NE

SW Elevação (m)

Elevação (m)

SW

0

0

-1200

3D invesion of magnetization vector

-1200

-

+

-2400

-2400

Susceptibility 0km

15.3km

3D invesion of magnetization vector

A

0km

19.7km

D

C

B

Salobo’s Mine (Cu/Au) Plunge to NE

Target (Cu/Au) Plunge to SW

SW

NE

Elevação (m)

0

-1200

-2400

0km

E

12.8Km

3D invesion of magnetization vector

F Furnas Deposit (Cu/Au) Plunge to NE

Unconsolidated sediments Laterito Magmatism A-type Granite (1.88Ga) Meta-granite (2.74Ga) Carajás Extensional Basin Meta-sediments (biotite-garnet cordierite xist) Meta-sediments (quartz-xist) BIF and metavolcano-sedimentar Meta-volcanic and BIF Basement Gneisses and Migmatites

Cupper Iron Gold Amethyst Manganese

Transpressional Structures Compressional Structure Transtensional Structures Silicous

-51º

High

-5º 40'

-50º30'

Low

Lineament Density

-5º 50'

-50º00'

-6º

Active Mines Active Garimpo Inactive Garimpo Mineral Deposits Occurrences Figure 15 - Results of detailed mapping along the Cinzento shear zone showing a correla on between the intensity of the magne c lineaments and the mineralized areas.

meteoric water and/or basin fluids (aquifers). The interac on of fluids with contras ng salinity and temperature favored the metal precipita on in the majority of the Carajás IOCG deposits (Monteiro at al., 2014). Manganese is another of the most important mineral resources at CMP. Two world-class mines are currently in opera on, including the Azul mine, owned by Vale and in produc on since 1985 (Figure 16), and the Buri rama mine, owned by a Brazilian private group (Mineração Buri rama) and in opera on since 2002. In addi on, there are two other remarkable manganese deposits in Carajás that both belongto Vale (Serra do Sereno, Antônio Vicente). The manganese-rich sedimentary successions of Azul and Serra do Sereno were deposited in the same geological context. They are represented by siliciclas c rocks (mudstones, red siltstones, manganesiferous pelites, coarse- to fine-

grained sandstones and conglomerates) of the Águas Claras Forma on. The sedimentary facies hos ng the primary Mn deposits are restricted to an offshore zone nearby the shoreface, and overlies thick turbidi c deposits rich in organic ma er (Figure 17).

Foto credits Vale

Figure 16 - Pit of the Azul manganese mine.

12


The metasedimentary sequences (quartzite, BIF, b a n d e d m a n ga n e s i fe ro u s o f t h e S e r ra d a Buri rama and Antônio Vicente regions evolved in the Neoarchean and were probably deposited during ri -related volcanic events. Besides their sedimentary origin, all known Mn deposits are also characterized by conjugate

Coastal Sandstone

tectonic and hydrothermal processes that remobilized and precipitated the manganese along the major structures, mostly into fault systems. T h i s t y p e o f o c c u r re n c e fo r m s t h e m a i n economically viable zones. Supergenic enrichment is the important manganese concentra on processes (Figure 18).

Progradation of sedimentary units and redox line migration

Mina do Azul Serra do Sereno

Tempestite Algae Carbonate

Carbonate Bank

Siltite with Mn-oxide

Mn Mn Black Shale

Mn

OXIDIZED ANOXIC

Buri rama BIF

Antônio Vicente

Compact Hema te Altera on Zone Ri Sequence

2.1 Ga

TTG - Grestone Belt Águas Claras Forma on Grão Pará Group Mod. from Teixeira et al., 2009

Figure 17 - The Azul and Sereno Mn deposits located in offshore zone nearby the shoreface, and overlying thick organic-rich turbidites of the Águas Claras Forma on. Also shown the Buri rama Mn deposit hosted in a metavolcano-sedimentary sequence (amphibolite, quartzite, BIF), probably deposited during ri -related volcanic events.

References: ARAÚJO, O.J.B., MAIA, R.G., 1991. Programa levantamentos geológicos básicos do Brasil. Projeto especial mapa de recursos minerais, de solos e de vegetação para a área do Programa Grande Carajás. Subprojeto Recursos Minerais. Serra dos Carajás, Folha SB.22-Z-A. Brasília: Departamento Nacional da Produção Mineral/DNPM - Companhia de Pesquisa de Recursos Minerais/CPRM, 152 p. CORDANI U.G., TASSINARI, C.C.G., KAWASHITA, K., 1984. A Serra dos Carajás como região limítrofe entre províncias tectônicas. Ciências da Terra, v. 9, p. 6-11. GRANGER, C.J.; GROVES, D.I.; TALLARICO, F.H.B.; FLETCHER, I.R., 2008. Metallogenesis of the Carajás Mineral province, southern Amazon craton, Brazil: Varying styles of Archean through Paleoproterozoic to Neoproterozoic base and precious-metal mineralization. Ore Geology Reviews, v. 33, p. 451-489. MONTEIRO, L.V.S., XAVIER, R.P., SOUZA FILHO, C.R. DE, MORETO, C.P.N., 2014. Metalogênese da Província Carajás. In Metalogênese das províncias tectônicas brasileiras. Editors: Maria da Glória da Silva, Manoel Baretto da Costa Neto, Hardy Jost, Raul Minas Kuyumjian. Belo Horizonte: CPRM. p. 43-92. MORETO, C.P.N., MONTEIRO, L.V.S., XAVIER, R.P., CREASER, R.A., DUFRANE, A., TASSINARI, C.C.G., SATO, K., KEMP, A.I.S., AMARAL, W.S., 2015. Neoarchean and Paleoproterozoic Iron Oxide-Copper-Gold Events at the Sossego deposit, Carajás Province, Brazil: Re-Os and U-Pb Geochronological Evidence. Economic Geology and the Bulletin of the Society of Economic Geologists, v. 110, p. 809-835.

13

SILVA, R.C.F., 2009. Evolução e gênese do minério de ferro hidrotermal nos depósitos da serra norte, Província mineral de Carajás. Tese (doutorado) Universidade Federal de Minas Gerais, Instituto de Geociências. TAVARES, F.M., 2015. Evolução Geotectônica do nordeste da Província Carajás. Tese de Doutorado. Instituto de Geociências, Universidade do Rio de Janeiro, Rio de Janeiro. 130 p. TEIXEIRA, N.A., FREITAS-SILVA, F.H., CORRÊA, C.R.A., ROSA, W.D., OLIVEIRA, J.K.M. DE, ROSENDO, O.S.C., PINHEIRO JR, V., 2009. Evolução geológica e mineralizações primárias da Província Mineral de Carajás. III Simp. Bras. Metalogenia, Gramado, RS. TEIXEIRA, N., SEABRA, A., CORRÊA, C., FREITAS, F., HUHN, S., SIEPIERSK, L., FILHO, B.A., SOUZA, C., 2010. A Província Polimetálica de Carajás e seus principais depósitos (Fe, Mn, Au, Cu, Ni, Pt) - Apresentação no Simexmin - ADIMB - Ouro Preto, MG. TEIXEIRA, N.A., MATOS, F.M.V., GANADE, C.E., KLEIN, E.L., DREHER, A.M., TAVARES, F.M., CAMPOS, L.D., PORTO, F., 2015. Carajás and Tapajós Mineral Provinces: Cratonic and Pericratonic Lithosphere Keel Metallogeny. Repositório Institucional de Geociências, CPRM. TRENDALL, A.F., BASEI, M.A.S., DE LAETER, J.R., NELSON, D.R., 1998. SHRIMP zircon U-Pb constraints on the age of the Carajás formation, Grão Pará Group, Amazon Craton. Journal of South American Earth Sciences, v. 11, n. 3, p. 265-277.


Area 1 - Azul mine Thick.

Stratigraphic profiles

Area 2 - Serra do Sereno

Description

5m

Mn

Fragments of lateritic manganese crust (colluvium) and manganese pisolites

3m

Mn

Manganesiferous lateritic crust

Mn 90 m

Mn Mn

Thick.

Thick layers of red-laminated pelite (red bed) interlayered with fine to mediumgrained sandstone and laminated manganesiferous pelite. Sandstones are structured with low angle cross-lamination and wave-ripple cross lamination. Synsedimentary faults occur restricted on some layers in the sequence. Manganese occur precipitated in faults/fractures by tectonic/hydrothermal processes. They form the main ore bodies (high ore content)

Stratigraphic profiles

10 m

Mn

6m

Mn

Manganesiferous crust forms on archean banded manganesiferous iron formation

8m

Metric layer of fluvial coarse-grained sandstone and conglomerate overlied discontinuously marine red and black pelites

40 m

Marine sequence of reddish pelites with lowangle and wave-ripple cross lamination. Convolute laminations recurrently occur along sedimentary package. Gold occur remobilized and precipitated in veins and disseminated in reddish pelites (Serra Pelada). These sedimentary rocks probably have offshore nearby to shoreface marine zone origin

redoxcline Layer of laminated organic-rich black shales

15 m

15 m

Turbiditic sequence. Intercalation of centimetric layers of fine to medium-grained sandstones with laminated organic richblack shales. Diagenetic pyrites disseminated in thin layers of sandstone

30 m

Metric layer of laminated manganesiferous pelite. Manganese occurs remobilized and precipitated in faults and fractures. On top of this package manganesiferous pelite occur interlayered with fine to medium-grained sandstones

redoxcline Thick layers of organic-rich black shales. Pyrite disseminated and remobilized in veins

15 m

Mn Mn

Intercalation of centimetric layers of fine to medium-grained sandstone with organic-rich black shales, organized in granodecrescent cycles (normal gradation) typical of turbidite sequence. Diagenetic pyrite occurs disseminated in thin sandstone layers and remobilized in veins. Convolute lamination, cross lamination and climbing ripples structured this turbiditic deposit. Erosion marks often occur at the base of the sandstone layers

45 m

Mn 120 m

Mn

Area 3 - Serra da Buritirama Thick.

Stratigraphic profiles

Thick.

Stratigraphic profiles

Mn

Fragments of lateritic manganese crust (colluvium) and manganese pisolites

10m

Mn

5m

Mn

Lateritic manganesiferous crust

5m

Mn

Mn

Massive medium to coarse-grained sandstone

8m

Foliated garnet-muscovite-biotite schist

Mn 15m

Mn Foliated medium to coarse-grained quartzite

5m

6m 20 m

Mn

Banded manganesiferous iron formation. Manganese occur remobilized and precipitated in faults and fractures

3m

Mn

Layer rich in secondary manganese

Fragments of lateritic manganese crust (colluvium) and manganese pisolites Lateritic manganesiferous crust Foliated medium to coarse-grained quartzite

4m

Banded manganesiferous iron formation

2m

Metasedimentary sequence composed of carbonate rocks and banded manganesiferous iron formation. Carbonate occur remobilized in veins. Manganese occurs locally parallel and cutting bedding as a result of secondary remobilization processes. This sequence is structured with tight fold and the manganese crust forms above this sequence.

Area 4 - Antônio Vicente

Description

10m

15 m

Description Fragments of lateritic manganese crust (colluvium) and manganese pisolites

Banded iron formation with restricted levels of manganese (banded manganesiferous iron formation). Manganese also occurs precipitated in planes of fracture and faults, forming highly mineralized levels. The greenish color is a result of alteration of banded iron formation Vulcanic sequence of basaltic and rhyolitic composition

Manganesiferous schist

5m

Mn

20 m

Mn

Banded manganesiferous iron formation. Manganese occur remobilized and precipitated in faults and fractures

Basaltic volcanic sequence interlayered with banded iron 130m

formation of silicate facies. Synsedimentary faults, accretionary lapilli and convolute

12 m

15 m

laminations occurs locally

Foliated medium to coarse-grained quartzite

Paragnaisse rich in muscovite and biotite. Bands rich in quartz and feldspar alternate with bands rich in mafic minerals. Fusion and remobilization occurs locally. It generates migmatites rich in feldspar and quartz along with refractory minerals in the border

Figure 18 - Stra graphic columns of Carajás manganese deposits.

14


Quadrilátero Ferrífero Project Joanna C.S. Araújo, Denise C. Brito, Jose A.D. Cavalcan , Marco A. Couto, Wilson L. Feboli, R.C.R. Ferreira, Frederico M. Freitas, Marcelo d.S. Marinho, Sabrina F. de Queiroz, Luiz P.P. Di Salvio, Luana D. Santos, Rosane N. Silva

The Quadrilátero Ferrífero Project is being developed by the Geological Survey of Brazil (CPRM) as part of its programs “Geological Geophysical Integra on and Predic ve Prospec vity Mapping of the Brasilian Shields” (Program I) and “Mineral Poten al Assessment of the Brazilian VolcanoSedimentary Sequences” (Program III). The Quadrilátero Ferrífero (QF) extends over an area of 2 7,000 km in central Minas Gerais State, Brazil (Figure 01). Its name is due to the form of abundant occurrences of iron forma on and iron ore. The aim of this project is to develop geological and metallogene c models for gold and base metals, expanding the knowledge on the economic poten al of this important Brazilian mineral province. In 2016 the preliminary mapping products of the project were presented. Theyinclude a mineral resources map at 1:100,000 scale of the QF and its surrounding area and geological maps at -44°30'

1:100,000 scale of the QF. These products are freely accessible from the online GeoSGB database (h p://geosgb.cprm.gov.br/). The QF region has been also covered by airborne geophysical surveys that include magne c (Figure 02), radiometric (Figure 03) and helicopter transient electromagne c (HTEM). The Geological Survey of Brazil (CPRM) has been modeling several areas with the Magne za on Vector Inversion (MVI) technique that provides good solu ons for characterizing magne c bodies, with the results that were a erward correlated with the structural control of gold mineralized bodies and their host rocks (Figures 04 and 05). These results were integrated with the HTEM and airborne radiometric data. The Precambrian sec on exposed in the QF consists of four major lithostra graphic units that include: (1) Archean metamorphic complexes composed of TTG (tonalite-trondhjemite-granodiorite) suites and high-44°0'

-43°30'

Itabira

BELO HORIZONTE Pará de Minas LEGEND Itacolomi Group: Quartzites -20°00'

Paleoproterozoics Greenstone belts Paleoproterozoics Greenstone belts: Banded Iron Forma ons Sabara Group: Greywacke-argilite sequences tuffs and diamic tes Minas Supergroup: Quartzites, phyllites and dolomites Minas Supergroup: Banded Iron Forma on Rio das Velhas Archean Grenstone Belt Ultramafic, mafic, volcanic and metassedimentary sequences Iron Major Deposits Gold Major Deposits Main Shear Zone or Fault Central Area NW Area Santa Barbara Area

Ouro Preto

-20°30'

Congonhas Carmo da Mata

0

15

30 km

Figure 01 - Simplified geological map of the Quadrilátero Ferrrífero project area showing the central (blue polygon) and NW (pink polygon) areas that are being mapped. The map shows the Rio das Velhas Archean greenstone belts and Minas Supergroup that host world-class gold and iron deposits, respec vely. Light blue polygon indicates the area modelled using the Magne za on Vector Inversion (MVI) technique.

15


-20°0' -20°30' 0

15

30 km

-44°0'

-43°30'

Figure 02 - Analy c signal map of the Quadrilátero Ferrrífero project area showing strong magne c anomalies associated with the BIF-rich Minas Supergroup.

occurs at the base of the sequence and contains the major Au deposits. Four deposi onal cycles were differen ated by Baltazar and Zucche (2007), with cycles I, II and III forming the Nova Lima Group (Figure 06).

K granites; (2) Archean Rio das Velhas Supergroup with typical greenstone belt sequence overlaid by lowto-medium grade metasedimentary units; (3) Paleoproterozoic Minas Supergroup and Sabará Group consis ng of low-to-medium grade metasedimentary rocks; and (4) Itacolomi Group composed of metasandstones and conglomerates. The Archean metamorphic complexes comprise 3.22.9 Ga gneisses and migma tes with typical TTG suite signatures. These rocks show well developed composi onal banding and several successive deforma on structures. Two genera ons of late intrusive granitoids are found in the region. The oldest has a calc-alkaline affinity and yields U-Pb zircon ages between 2.78-2.76 Ga while the youngest shows highK signatures and was dated between 2.75-2.6 Ga. The intrusive bodies have dome shapes with diameter >50 km. Both isotropic fabrics and discrete shear zones are developed especially along the contact with the supracrustal units.

Cycle I occurred between 2,800-2,780 Ma based on ages determined on the mafic and felsic rocks. It predominantly comprises mafic-ultramafic (tholeii c-koma i c) flows intercalated with chemical sedimentary rocks. The cycle is related to the ini al extensional stage of the greenstone belt development, with the deposi on of sediments contemporaneous with the volcanic flows that formed the submarine oceanic plains. Cycle II encompasses a clas c-chemical sedimentary associa on and distal turbidites in the eastern sector of the Quadrilátero Ferrífero. It was deposited during the ini al stage of the subduc on phase. In the southern sector of QF it includes coastal sandstones (with medium-to-large scale cross-bedding, ripple marks, herringbone crossbedding, sandstone-siltstone) and resedimented associa ons (graywacke-argillite).

The metavolcano-sedimentary rocks of the Rio das Velhas Supergroup are subdivided into the Nova Lima and Maquiné Groups (Figure 06). The former

16


-20°0' -20°30'

0

15

30 km

-44°0'

-43°30'

Figure 03 - Ternary gamma-spectrometry map (K, eU, eTh) of the Quadrilátero Ferrífero project area. The mafic and ultramafic rocks of the Rio das Velhas Supergroup basal unit are poor in radioelement concentra ons and marked by dark zones. The regions with the highest K concentra on are interpreted as hydrothermal zones commonly associated with gold deposits.

Cycle III mainly outcrops in the northern sector of QF and comprises felsic volcanic, volcaniclas c and resedimented rocks (monomic c and polymic c breccias, conglomerate-graywacke, graywackesandstone, graywacke-argillite). These rock associa ons indicate a submarine fan environment, progressively evolving to non-marine successions and the building of felsic volcanic edifices during the island arcs forma on. The felsic metavolcanics were U-Pb dated to 2,776 Ma and 2,772 Ma. U-Pb zircon da ng of the volcaniclas c rocks at 2,792 Ma, 2,773 Ma, and 2,751 Ma suggests that the felsic volcanic event lasted about 40 Ma as part of the greenstone belt forma on. This magma sm was found to be coeval with the oldest QF group of calkalkaline granitoids. Cycle IV includes clas c sedimentary rocks belonging to a non-marine lithofacies associa on (conglomerate-, coarse-grained and fine-to-medium grained sandstones) of the Maquiné Group. Their deposi onal environments were interpreted as braided-river plains and alluvial fans in a retroarc

17

foreland basin that was filled with debris from the previous cycles. Gold deposits in the Rio das Velhas greenstone belt are structurally controlled and associated with hydrothermal altera ons along Archean thrust shear zones. They were classified by Lobato et al. (2001) as orogenic gold deposits formed between 2.72-2.67 Ga, during the final stages of the Archaean orogenesis (Figure 08). The main mineraliza on styles are: (1) structurally controlled sulfide-replacement zones in BIF; (2) disseminated sulfides in hydrothermal rocks along shear zones; (3) quartz-carbonate-sulfide veins in mafic-felsic volcanic and clas c rocks. The goldbearing mineraliza ons are disseminated in massive sulfide strata-bound ores of the Rio das Velhas Supergroup. They likely formed as epigene c replacements in oxides and sulfides, or carbonate facies BIF (Figures 09 and 10). The chemical sediments make most of the country rocks of the gold deposits. The fluids at the orgin of these deposits were 18 enriched in CO2 and O and reached temperatures between 325-400°C for low-to-moderate salinity.


A

Top View SE Bottom View

A 7790000

Córrego do Sítio II

B

Pilar 5k

m

Córrego do Sítio I 7785000

A B

655000

660000

Magnetic Susceptibility Isosurface (>0.02 SI)

NE View 0.04560 0.01120 0.00724 0.00464 0.00390 0.00316 0.00242 0.00168

~1000m

0.00094 0.00020

Magnetic Susceptibility (SI Units)

Figure 04 A - Magne za on Vector Inversion (MVI) results for the Santa Bárbara region showing a strongly magne zed body (k>0.02 SI) associated with BIFs and that correlates well with a NE-SW linear magne c anomaly. The magne c body shows a strong remanent magne za on as indicated by the vectors direc ons, with a synform structure (NE view) about 1000 m deep and 5 km long in the NE direc on. This magne c body can possibly be correlated with the Conceição syncline that is associated with the Córrego do Sí o Lineament. Further studies including MVI technique and integra on with the HTEM modeling could help to be er understand this structure and its associa on with gold deposits along this lineament.

B R i o d a s Ve l h a s S u p e r g r o u p MAQUINÉ GROUP (Clastic metassedimentary association - coastal and fluvial)

Casa Forte Fm. - Chica Dona Un. Casa Forte Fm. - Córrego do Engenho Un. NOVA LIMA GROUP

Palmital Fm. - Rio de Pedras Un. Mindá Un. (marine clastic metassediments) Córrego do Sítio Un. (marine clastic metassediments) Santa Quitéria Un. (BIFs) Santa Quitéria Un. (chemical pelitic metassediments) Ouro Fino Un. (plutonic metavulcanic rocks) Quebra Osso Un. (metaultramafic and mafic rocks) Gold Mine

Barão de Cocais

Santa Bárbara CÓRREGO DO SÍTIO II PILAR

CÓRREGO DO SÍTIO I

0

4

8km

Figure 04 B - Geological map of the Santa Bárbara region. The main rock units comprise a metamorphosed succession of schistose sediments of the Nova Lima Group, Rio das Velhas greenstone belt, which hosts lode-gold mineraliza on associated with BIFs (Pilar and Córrego do Sí o II deposits) and quartz-carbonate-sulfide-sulfosalt-rich veins (Córrego do Sí o I deposit).

18


A

São Sebastião Deposit

7850000

ESE View Pequi Anomaly

Conceição do Pará Anomaly

7830000

7850000

7840000

7830000

Magnetic Susceptibilty Isosurface (>0.15 SI)

0.01361 0.00522 0.00270 0.00253

N view

0.00235 0.00218 0.00201 0.00183

7810000

0.00166 0.00148 0.00131 0.00096 0.00079 0.00061 0.00044

510000

530000

São Sebastião Deposit

0.00026 0.00009

550000

520000

504000

520000

536000

7840000

B

Magnetic Susceptibility (SI Units)

530000

0

10km

7824000

5

LEGEND

Rio Pará

Shear zones and lineaments Agalmatolite deposits Gold deposits and occurrences Quartz digging mines Recent sedimentary covers Proterozoic sediments of Bambuí Group

São Sebas ão Deposit

Rio São João

agl

Metahidrothermalites with subordinate agalmatolites (agl) e magnetitites (mt). SIN TO LATE TECTONIC GRANITOIDS Tonalite to granodiorite granitoids (~2,7 Ga) mt

7808000

RIO DAS VELHAS SUPERGROUP MAQUINÉ GROUP Quartzites with subordinate intercalations of oligomitic metaconglomerates NOVA LIMA GROUP Metagreywackes, metapelites with ff metaconglometares, metarenites, metatuffs, banded iron formations (ff) intercalations. Fine-grained clastic metasediments interlayered with meta-lapilli-tuffs and metagglomerates. mu Metamafic volcanic rocks with minor ms ff intercalations of metaultramafic (mu), metavolcanoclastics, cherts (ms) and banded iron formations (ff). CRYSTALLINE BASEMENT Gneisses and migmatites of Divinópolis Complex

Figure 5A - Magne za on Vector Inversion (MVI) results for the Pará de Minas region showing a strongly magne zed body associated with the NW lineament (Pequi anomaly - shear zone). The NW por on of this magne c body is likely correlated with magne c BIFs, with an ellipsoidal shape dipping 40-45° to the NW. This magne c body is of great importance for prospec vity, with its interpreta on that could greatly contribute to the metallogenic and structural understanding of the area. Figure 5B - Simplified geological map of the NW area showing the Rio das Velhas Supergroup lithostrigraphic units, the main gold, agalmatolite and quartz occurrences, with the São Sebas ão deposit highlighted

19


Stra graphic Columns of the Rio das Velhas Greenstone Belts

1

v v v v v v

2

v v v

v v v

Lithological Association Sandstone-conglomerate (matrix and clast-supported)

Continental alluvial fan and fluvial deposits

Depositional Systems

Sandstone-siltstone

Proximal volcanogenic turbidites

Greywacke-argilite,

Volcanogenic distal turbidites of Na-rich felsic source

500 0 Meters

4

MAQUINÉ GROUP

Casa Forte Fm. Rio das Pedras

CYCLE III

Mestre Caetano

Volcanoclastic rocks of emergent island arcs, Volcanogenic conglomerate-greywacke, breccias braided sandstones, alluvial fan breccias (polymitic and monomitic), greywacke-sandstones fluvial and conglomerates

Ribeirão Vermelho

Sandstone

Coastal sediments (aeolian, tidal plain)

Andaimes (São Bartolomeu Domain)

Graywacke-argilite (calc-silicatic rocks and banded iron formations)

Resedimented turbidites (distal or proximal) of felsic and mixed sources

Pelites and banded iron formations

Pelagic and chemical marine sedimentary rocks

3 1000

Stratigraphic Unit CYCLE IV

NOVA LIMA GROUP

CYCLE II

Catarina Mendes, Pau d’Óleo, Córrego Paina, Fazenda Velha (São Bartolomeu Domain) Córrego do Sítio, Mindá (Santa Bárbara Domain)

CYCLE I

Morro Vermelho Ouro Fino Quebra-Osso, Córrego dos Boiadeiros Complex

RIO DAS VELHAS SUPERGROUP

Santa Quitéria (Santa Bárbara Domain)

Basalts and banded iron formations Subaqueous mafic-ultramafic-volcanics Komatiites, basalts (cherts and banded iron formations) partially associated with chemical sediments

Gold mines: (1) Morro Velho, Cuiabá, Lamego; (2) Córrego do Sítio; (3) São Bento; (4) Raposos

Figure 06 - Stra graphic column of the Rio das Velhas Greenstone Belt (adapted from Baltazar and Zucche , 2007). fluvial sandstone Proximal Turbidite turbidite

Agglomerate

Distal Turbidite Volcanoclastic BIF Basal c Flows - Pillow Lavas

Basal c Flows - Pillow Lavas Banded Iron Forma on, Cherts Diferen ated Spinifex - Flows Sheet-Flows Facies Olivine Orthocumulate Olivine Adcumulate Dunite Lenses - Channel Facies

A ic

Pillow Basalts

Alluvial Fans Braided Rivers BIF Exhalative Fe-Mn-Si Sediments

lc

a

o VTurbidites

n

r

c

Vulcanoclastic Distal Turbidites

Basalts

Potassion-Rich Granites

Cherts- B I F

Poding of Magmas Komatiite In Mid-Ocean Ridge Archean Ocean Floor

TTG

Partial melting of hydrated mantle Asthenospheric Metasomatized Aqueous fluid Mantle

Deep Water Sediments Turbidites

Melting of oceanic crust Dehydration of Oceanic crust

Decompressional Melting Melt of Sediments

Breakdown of Serpentine and amphybole

Figure 07 - Schema c model of greenstone belt evolu on.

20

Melting of Sodium -Rich Granites Partial Melting of Hydrated Mantle Magma Crack Propragation


SB

RdV I

RdV II

Mam

20

Machado et al. (1992, 1996) Noce et al. (2005)

GOLD MINERALIZATION Pb/Pb (Apy-Py) São Bento Mine 2.65 Ga De Witt et al., (1996)

16

Frequency

ID-TIMS (N=21)

2761 Ma 12

LA-ICP-MS (N=23) Machado et al. (1996)

U/Pb SHRIMP Morro Velho and Cuiabá Mines 2672±14 Ma Lobato et al., (2007) Lamego Mine 2730±42 Ma Martins et al. (2016)

SHRIMP (N=45) Noce et al. (2005) Hartmann et al. (2006)

2850 Ma 8

All zircons are < 10% disc. Bin width 40 Ma

2943 Ma 3174 Ma

Density probability plot

4

0 2800

3000

3200

3400

3600

3800

Age (Ma) Figure 08 - Combined histogram and probability density diagram of detrital zircon U-Pb ages from rocks of the Rio das Velhas Supergroup. Ver cal bands and yellow star mark the main magma c events and gold mineraliza ons in the Quadrilátero Ferrífero region, respec vely. The data was compiled from Farina et al. (2015) and linked references.

Courtesy Rodrigo Martins Figure 09 - Rock exposure of banded and massive sulfide ores. Insert photo of a drill core sec on presen ng free gold in a quartz vein (Cuiabá mine).

21


Figure 10 - Rock exposure of sulfide-rich BIF hos ng the Lamego orogenic gold deposit from the Rio das Velhas Greenstone Belt (Lamego mine operated by AngloGold Ashan - photo credit: Joanna C.S. Araújo).

References: BALTAZAR, O.F., ZUCCHETTI, M., 2007. Lithofacies associations and structural evolution of the Archean Rio das Velhas greenstone belt, Quadrilátero Ferrífero, Brazil: A review of the setting of gold deposits. Ore Geology Reviews, v. 32, n. 3, p. 471-499. FARINA, F., ET AL., 2015. The ArcheanePaleoproterozoic evolution of the Quadril_atero Ferrífero (Brasil): Current models and open questions, Journal of South American Earth Sciences (2015), http://dx.doi.org/10.1016/ j.jsames.2015.10.015. LOBATO, L.M., RIBEIRO-RODRIGUES, L.C., VIEIRA, F.W.R., 2001. Brazil´s premier gold deposits. Part II: geology and genesis of gold deposits in the Archean Rio das Velhas greenstone belt, Quadrilátero Ferrífero. Mineralium Deposita, v. 36, p. 249-277.

22


Tapajós Project Fhábio G.R. Pinheiro, Cesar L. Chaves, João M.R. de Castro, Manoel C.d.C. Neto, Marcelo L. Vasquez, Vanessa L. Cruz

The Tapajós Project is being developed by the Geological Survey of Brazil (CPRM) as part of its program “Geological Geophysical Integra on and Predic ve Prospec vity Mapping of the Brazilian Shields” (Program I). This project aims to determine the regional and local controls of the known gold and base metals mineraliza ons, and to indicate favorable areas for mineral explora on. The project encompasses por ons of two geochronologically Authors: Raphael T. Correa, Bruce F. Chiba, Marcelo Vasquez, Cesar Chaves, Fhábio Pinheiro.

-58°

dis nct provinces that are located along the southwestern edge of the Amazon Craton (northwest Brazil): Tapajós-Parima (2.03-1.88 Ga) and Central Amazônia (1.88 Ga) (Santos, 2003). According to Cordani et al. (1984) the Archean Amazon Craton is surrounded by progressively younger orogenic belts that amalgamated to form a coalescence of accreted terranes (Figure 01).

-57°

-56° Magnetic Lineaments Falt

To c

an

Magnetic Blocks

tiz

inh

Au deposits

oG

old

-6°

B

Tre n

-55°

d

Simplified Lithostratigraphic Units Fanerozoic sedimentary rocks. Cachoeira Seca/Suite: gabbros e anortosites Buiuçu formation: conglomerates, sandstone Maloquinha Suite: sienogranites, monzogranites, quatz-syenite Moraes Almeida Formation: Ignibrites, trachytes Ingarana Suite gabbros and anortosites Bom Jardim Formation: andesites Paraurai Suite/granite unit Paraurai Suite/granodiorite unit: Monzogranites, granodirites and Salustiano Formation: Rhyolites and dacites Tropas Suite: Tonalites, monzonites and granodiorites Jacareacanga Group: Shists pelites, metamafic, metautramfic and quartzites Creporizão Suite: monzonites, sienogranites, Chapeu do Sol Formation – Ryolites and andesites -8° Vila Riozinho Formation: Ignibrites, rhyolites and andesites Cuiú-Cuiú Complex - Tonalites and monzonites Comandante Arara Formation - Ignibrites and trachytes Castelo dos Sonhos Formation - Sandstone and conglomerate

Geological Section

Major Gold Corridor

A

-7°

0

25

50km

LTCZN

A

B Maloquinha Suite: sienogranites, monzogranites, quatz-syenite Moraes Almeida Formation: Ignibrites, trachytes

Ingarana Suite gabbros and anortosites Paraurai Suite/granite unit Cuiú-Cuiú Complex - Tonalites and monzonites

Creporizão Suite: monzonites, sienogranites, Vila Riozinho Formation: Ignibrites, rhyolites and andesites

Falt Au quartz veins

Figure 01 - Geological map of theTapajós project area. The Euler deconvolution of magnetic and gravity data (middle panel) was used to delineate the main geological contacts and faults. The geological model (lower panel) shows that the Tocantizinho gold trend is associated to a deep crustal discontinuity.

23


The Tapajós Gold Province (TGP) (Cou nho, 2008) is located on the south-central por on of the Amazonian Craton, in the states of Pará and Amazonas. It has a total historical produc on of about 780 tons of gold, extracted mainly by handcra ed digging of rivers and streams, and subordinately from hundreds of ar sanal small open pits and underground mines. There is currently only one mine in ac vity at Tapajós (Palito mine, 668 KOz Au, Serabi Gold) and one major project under development (Tocan nzinho, 1,824 MOz Au in reserves, 2.115 MOz Au in resources, Eldorado Gold). Other significant deposits are s ll in explora on phase, e.g. São Jorge (1,584 MOz Au, Gold Mining), Coringa (913 KOz Au, Anfield), Boa Vista (336 KOz,

Gold Mining). A total resource of 7.5 MOz has been reported from the five main gold deposits in the region, which are under development mainly by Canadian and Australian mining companies. The basement rocks of the Tapajósarea comprise plutonic rocks, gneisses, migma tes (2.04-2.02 Ga Cuiú-Cuiú Complex) and a rela vely thin volcanosedimentary unit (Jacareacanga Group). These rocks have calc-alkaline affini es with medium-K and juvenile isotopic signatures. The Cuiú-Cuiú granitoids are characteris c of magma c arcs or ac ve con nental margins (Almeida et al., 2007; Vasquez et al., 2008). Figure 02 shows underformed plutonic-volcanic sequences that par ally cover the basement, including few that are considerated by 1893-1869 Ma

1898-1881 Ma

2002-1959 Ma

1893-1869 Ma

3 2033-2005 Ma

2020-2012 Ma

1892-1879 Ma

6

4

1882-1862 Ma

5

1997-1956 Ma

7

1907-1893 Ma

1 ~2050 Ga 1 2 3 4 5 6 7

2033-2005 Ga

2

Jacareacanga Group (2,050 Ga) - pelític shist, quartzites, metamafic and metaultramafic Cuíu-Cuíu Complex - Tonalites, Monzogranites and migmatites Comandante Arara Formation - Ignibrites, rhyolites, andesites e vulcanoclástic Crepori / Vila Riozinho Event - Ignibrites traquites, andesites, Ryolites, vulcanoclastic and sediments. Tropas Event- Tonalitos e Monzogranitos Dacitos, latitos, andesitos e basaltos Maloquinha / Iriri Event - Sieno granitos, monzogranitos e granitos Ignibritos, riolito, dacitos e traquitos Parauari / Bom Jardim Event - Monzogranites e diorites, dacites and basalts

Figure 02 - Schema c representa on showing the basement of the Tapajós area, including the Cuiú-Cuiú complex and Jacareacanga volcano-sedimentary sequence, with four main dated plutonic-volcanic events that were accompanied by sedimentary events.

Fraga et al. (2015) as belonging to the Uatumã Siliceous Large Igneous Province (SLIP). The SLIP plutonic and volcanic rocks have geochemical signatures compa ble with an A-type or high-calcium alkaline suite (Vasques and Dreher, 2011). They comprise several volcanic lithostra graphic units (e.g. Iriri, Bom Jardim) and granitoids (e.g. Maloquinha, Velho Guilherme, Rio Dourado, Parauari, Tropas), with ages ranging between 1.90-1.86 Ga (Fraga et al., 2015). Rhyacianand few Neoarchean ages for the Tapajós Domain were inferred using Sm-Nd system, with εNd(t) between -6.7 and -0.7, whereas Meso-toNeoarchean ages were inferred for the Iriri-Xingu

Domain, with εNd(t) between -5.35 and -12.1. The volcanic rocks dominantly comprise rhyoli c and daci c ignimbrites, also described as ash-flow tuffs. Felsic- to andesi c lavas, subvolcanic rocks, and ashfall tuffs occur subordinately as compared to the extensive ignimbrite deposits. Lithology and erup on mode of the Vila Riozinho volcanic unit appear similar to the older Iriri unit. The unit consists of strongly welded daci c ignimbrites with phenocrysts of plagioclase, K-feldspar and subordinate quartz crystals, fla ened pumice clasts, in a microcrystalline, felsic, flow-foliated matrix (Figure 03). Other rock-types in this unit occur as trachy c and andesi c flows (Figures 03, 04 and 05).

24


PI

Qz

Kf

PI

Kf

Kf

Pm

Pm Kf

Pm

Foto credit Ana Dreher

Foto credit Ana Dreher

Figure 03 - Daci c ignimbrite of the Vila Riozinho Forma on containing plagioclase (Pl) and K-feldspar (Kf) crystals, and fla ened pumice clasts (Pm) in a microcrystalline felsic flow-foliated matrix. Thin sec on of sample MV-265 viewed under plane polarized light (horizontal scale: 1 mm).

Foto credit Ana Dreher

Figure 04 - Welded daci c-to-andesi c ignimbrite belonging to the Iriri unit and showing zoned plagioclase crystals (Pl), altered mafic phases and pumiceclasts (Pm), in a very fine-grained groundmass. Thin sec on of sample CE-24 viewed under plane polarized light (horizontal scale: 1 mm).

Three main types of gold mineraliza on are known at TGP (Figures 06, 07 and 08): (1) Compressional shear veins associated with the Jacareacanga and Cuiú-Cuiú units, with restricted altera ons of sericite, carbonate and chlorite (Espírito Santo, Bom Jesus, Pepeu, Chico Torres, Jerimum de Cima garimpos). These mineraliza ons are considered as orogenic gold or intrusion-related type deposits (Cou nho, 2008; Vilas et al., 2013; Assunção and Klein, 2014); (2) Extensional epithermal high-grade quartz veins with comb texture and adularia. These mineraliza ons are hosted by the plutonic-volcanic sequences of Creporizão-Riozinho (2,000-1,968 Ma), Parauarí-Moraes de Almeida (1,898-1,880 Ma) and Maloquinha-Iriri (1,890-1,864 Ma), and found as well from the ar sanal extrac ons (garimpos) of Carneirinho, Goiano, Pison and Abacaxis (Dreher et al., 1998), and; (3) High sulfida on low-grade gold deposits (e.g. V3) (Jacobi, 1999; Juliani et al., 2014).

Au

Palito Mine V3

Au

Goiano

Phylic

Argilic Altera on

Au

Sub-volcanic Intrusive Related to Maloquinha Granite (Synchronous to Shearing)

Chlorite Filled Sheets or Faults (Chl-Carb-Fluorite) Quartz Sulfide Veins with Strong Chlorite Wall Rock Alteration Sinous Veins Hosted by Maloquinha Granite

Magma

Leandro, et al, 2015 unpublished Legend Maloquinha and Parauari Granites Creporizão, Cuiú-Cuiú Granites

Figure 06 - Schema c model of Tapajós gold mineraliza ons. Note that the mineralized veins and subvulcanic bodies are controlled by bri e shear zones. Palito mine in detail.

Bom Jesus Phillic Alteration São Jorge

Carneirinho

Ingarana

Davi 1,891 Ma

Abacaxis

Tapajós Gold Mineralizations

Davi

Figure 05 - Densely welded rhyoli c ignimbrite of the Moraes de Almeida sequence, containing K-feldspar (Kf) and quartz (Qz) crystals, and a folia on defined by fla ened aligned pumice lapilli (Pm). Thin sec on of sample AT-02 A viewed under plane-polarized light (horizontal scale: 1 mm).

Pepeu

Parauari

Moraes Gomes Creporizão Espirito Santo Maloquinha Jacareacanga - Cuiú-Cuiú

1.997 Ma Guarim

2.0 - 1.95 Ga

Maloquinha Modified from Santos, 2008

Figure 07 - Schema c representa on of small gold deposits in the Tapajós region. Note the predominant occurrence of quartz veins in the shear bri le zones surrounded by phyllic altera on.

25


Vuggy Sílica

Winding pyrite-quartz veins with hematite in alteration halo in Maloquinha granite

Epithermal breccia with quartz-sericite alteration

Mineralized quartz-chlorite-pyrite-chalcopyrite veins in ductile shear zone. Note the chlorite alteration halo restricted to the vein edge in Maloquinha granite.Palito underground mine.

Quartz-fluorite vein with druses and chlorite alteration halo in Maloquinha granite

Mineralized quartz-chlorite-pyrite-carbonate veins in ductile shear zone. Note the chlorite alteration halo restricted to the vein edge in Maloquinha granite. São Chico underground mine

Figure 08 - Geological features of Tapajós gold mineraliza ons.

The geotectonic evolu on of TGP and adjacent terranes is subjected to strong scien fic debate. Teixeira et al. (2014) suggested that the TGP gold d e p o s i t s a re re l ate d to i nt ra - co n n e nta l magma sm originated at a ri ed cratonic keel, with asthenospheric melts rising through the ri m a rg i n s a t 2 . 0 - 1 . 8 8 G a ( F i g u re 0 9 ) . T h e predominance and large volume of felsic magma can be explained by the influence of a mega plume that pounded at the base of the crust, yielding extensive underpla ng and bimodal volcanism

(Santos, 2015) (Figures 10 and 11). .The TGP gold mineraliza on has about the same age as the Maloquinha and Parauarí plutonicvolcanic sequences, which are derived from a huge con nental magma c event that affected a large por on of the Amazon Craton (Fraga et al., 2015) (Figures 12, 13 and 14).

26


Tapajós Gold Mineralization - Geotectonic Setting

Parauarí

NE

Maloquinha

Araguaia Ofiolite Cuiú-Cuiú

Carajás

Lithosphere Keel

SCLM Keel Edge Figure 09 - Schema c representa on of TGP hosted by a volcanic-subvolcanic-plutonic magma c system, which originated from a mafic underpla ng-plume event. During the Paleoproterozoic a large (mega) plume likely was deflected and channelled beneath the base of a ri ed cratonic keel about 100 km-thick. The TGP is the result of disturbances affec ng the Subcon nental Lithospheric Mantle (SCLM) during ri ing events and therefore is not related to the forma on of a convergent plate margin. . Cuiú-Cuiú

Uatumã LIP - 1.90 - 1.86 Ga Intracon netal Ri

Cuiú-Cuiú Mobile Belt

Carajás

Uatumã: Maloquinha-Iriri-Parauari

Bacajá

Bacajá Mobile Belt

SCLM Stagnant Slabes

410 km

1893-1864 Ma

660 km

?

?

Figure 11 - Schema c representa on of the Uatumã SLIP geotectonic se ng. The large (mega) plume may have been triggered by gravita onal fall of Transamazonian slabs in the Transi on Zone, in a similar model as proposed by Pirajno and Santosh (2014). .

Slabe avalanche Lower Mantle Super pluma

Figure 10 - Fraga et al. (2015) proposed that the subduc on of oceanic plates adjacent to the Amazon Craton may have favoured the forma on of the Siliceous Large Igneous Province (SLIP) of Uatumã. Pirajno and Santosh (2014) explained the worldwide development of enormous amounts of felsic magmas by plumes triggered by gravita onal fall of destabilized pieces of ocean floor in the Transi on Zone.

Core-Mantle Boundery

Epitermal Mineraliza on 1.869 - 1.870 Ga (Juliani et al. 2014)

1

3

Tapajós post-calderas Volcanoes Ash flow, andesite and tuffs

Gold Mineraliza on Porphyry

Phylic Altera on

2

1892-1879 Ma

Parauari and Maloquinha magma c chambers

1. Epitermal deposits in breccias and veins 2. Qz Veins close to the magma c chamber 3. Mineraliza on in phylic altera on zones

1.882-1.862 Ga

Intracon nental magma sm

Figure 12 - Schema c representa on of Tapajos volcanic se ng formed by ignimbrites, rhyoli c and daci c flows erupted from subaerial calderas (modified from Juliani et al., 2014). The gold mineraliza on is related to sub-vulcanic phorphyry, plugs and quartz veins surrounded by a phyllic altera on zone.

27


0

5

10km

Figure 13 - Maloquinha and Parauari volcanic region formed by the coalescence of calderas and covered by ignimbrites, rhyolites and dacites (taken from Juliani and Fernandes, 2010).

52°W

64°W

CI

Atl an tic

VENEZUELA GUIANA

O

10°N

e a

CA

c

n

GUIANA FRANCESA

T

Phanerozoic cover LATE-OROSIRIAN - CALYMMIAN - MESOPROTEROZOIC Undivided units

SURINAME

A

BA

CS

Sedimentary rocks (>1,78 Ga)

g

BRASIL

nas

mazo

Rio A

jós

Ne

ro OROSIRIAN Calc-alkaline A-type granites with high-K and gneisses, charnockites e granulites (1,95 -1,93 Ga) Supracrustal Rocks in Greenschist facies (1,95 Ga) Orocaima Magmatism Granitoids and A-type calc-alkanine vulcanic rocks with high-K (CA) and S-type calc-alkaline granitoids (CS) with high-K (1,98-1,95 Ga). (=) Granitoids ~1,99 Ga in the Província Alta floresta (PA) with archean remains

Tap a

Uatumã Magmatism Felsic vulcanic rocks (to interm.) and undivided granitoids. Rio Calc-alkaline affinity A-type with high-K (1,90-1,86 Ga)

Rio

Supracrustal rocks in anfibolite to granulite facies and S-type granites (2,00 Ga?) Supracrustal rocks in greenschist to anfibolite facies

gu Xin

Iriri

DT

Granitoids and greenstone belt sequences (2,21-2,07 Ga) and granite-gneiss terrains ARCHEAN WITH PALEOPROTEROZOIC REWORKED CI Felsic granulites and gneiss with archaen heritage reworked in the Orosirian (Complexo Imataca - CI) Archean units in Bacajá (BJ) and Santana do Araguaia domains and Amapá Block (AP), reworked in Rhyacian ARCHEAN Carajás Domain (3,0-2,5 Ga) Rio Maria Domain (>3,0-2,8 Ga)

BJ

Rio

Rio

Granitoids and calc-alkaline gneisses (T-Trairão; A- Anauá; C-Cuiu-Cuiui) (2,04- 2,02 Ga), granite-gneiss terrains RHYACIAN Granulites and charnockites (2,06Ga) Intracatonic to platform sedimentary sequences (siderian/ rhyacian?) C

DI

PA

Approximate limit between Tapajós (DT) and Iriri-Xingu (DI) domains from the isotopic signature Cinturão Cauarane-Curuni shear zone

=

=

SA

=

200 km

Figure 14 - Geological map of the Amazonian region showing the con nental extension of the Uatumã SLIP as highlighted in orange (Fraga et al., 2015).

28

10°S


References ALMEIDA M.E., MACAMBIRA, M.J.B., ELMA, C.O., 2007. Geochemistry and zircon geochronology of the I-type high-K calc-alkaline and S-type granitoid rocks from southeastern Roraima, Brazil: Orosirian collisional magmatism evidence (1.97-1.96 Ga) in central portion of Guyana Shield. Precambrian Research, v. 155, p. 69--97. CAMPOS, L., TEIXEIRA, N.A., GANADE, C. Relatório Interno SGB-CPRM Atividades de Campo, Tapajós, Alta Floresta, 2015, unpublished. COUTINHO, A.M., 2008. Província Mineral de Tapajós e Mapa Previsional para Ouro em SIG. CPRM, Rio de Janeiro, 4209. DREHER, A.M., VLACH, S.R., MARTINI, S.L., 1998. Adularia associated with epithermal gold veins in the Tapajós Mineral Province, Pará state, northern Brazil. Brazilian Journal of Geology, v. 28, n. 3, p. 397-404.JACOBI, M., 1999. The discovery of epithermal Au-Cu-Mo Proterozoic deposits in the Tapajós Province, Brazil. Brazilian Journal of Geology, v. 29, n. 2, p. 277-279. JULIANI, C., FERNANDES, C.M.D., 2010. Well preserved Late Paleoproterozoic volcanic centers in the São Felix do Xingu region, Amazonian Craton, Brazil. Journal of Volcanology and Geothermal Research, v. 191, p. 167-179. KLEIN, E.L., ALMEIDA, M.E., ROSA-COSTA, L.T., 2012. The 1.89-1.87 Ga Uatumã Silicic Large Igneous Province, nothern South America. Large Igneous Province Comisssion, November 2012 LIP of the Month. LÊDA, M.F., VAZQUES, M.L., ALMEIDA, M.E., REIS, N., 2015. A influência da orogenia eo-orosiriana na formação da slip Uatumã, parte central do craton amazônico CPRM - Serviço Geológioco do Brasil (inédito).

29

JACOBI, M., 1999. The discovery of epithermal Au-Cu-Mo proterozoic deposits in the Tapajós Province, Brazil. Brazilian Journal of Geology, v. 29, n. 2, p. 277279. JULIANI, C., FERNANDES, C.M.D., 2010. Well preserved Late Paleoproterozoic volcanic centers in the são Felix do Xingu region, Amazonian Craton, Brazil. Journal of Volcanology and Geothermal Research, v. 191,p. 167-179. SANTOS, J.O.S., 2003. Geotectônica dos Escudos das Guianas e Brasil Central. In: BIZZI, L.A.; SCHOBBENHAUS, C.; VIDOTTI, R.M.; GONÇALVES, J.H. Geologia, tectônica e Recursos Minerais do Brasil. Brasília: CPRM. p. 198.TEIXEIRA, N.A., CAMPOS, L.D., CARVALHO, M.T.N., CUNHA, L.M., 2015. Porphyry or not porphyry; That´s not the only question. 2015. Repositório Institucional de Geociências, CPRM. VASQUEZ, M.L., DREHER, A.M., 2011. Uma avaliação da estratigrafia dos eventos magmáticos de 1900-1860 Ma do Cráton Amazônico. IN: 12° SIMPÓSIO DE GEOLOGIA DA AMAZÔNIA. BOA VISTA, RESUMOS EXPANDIDOS. VASQUEZ, M.L., ROSA-COSTA, L.T., SILVA, C.M.G., KLEIN, E.L., 2008. Compartimentação tectônica. IN: VASQUEZ M.L., ROSA-COSTA, L.T. (Eds.) Geologia e Recursos Minerais do Estado do Pará: texto explicativo dos mapas Geológico e Tectônico e de Recursos Minerais do Estado do Pará. Escala 1:1.000.000, Belém, CPRM, p. 39-112.


Juruena-Teles Pires Project Gilmar J. Rizzo o, Cléber L. Alves, Francisco S. Rios, Tiago B. Duarte, Leonardo B.L. Lopes, Gabriel d.F. Gonçalves

The Juruena-Teles Pires Project is being developed by the Geological Survey of Brazil (CPRM) as part of its program “Geological Geophysical Integration and Predictive Prospectivity Mapping of the Brazilian Shields” (Program I). The Project is focused on the Alta Floresta Gold Province (AFGP) which historically has produced around 300 tons of gold (Figure 01). This province is located in the north of Mato Grosso State and consists of a 600 km long section of alluvial and primary gold occurrences, extending from the Moriru

-59º

Peixoto de Azevedo and Matupá towns (eastern part) to the Juruena river (western part). This region also includes the Zn-Pb-(Cu) deposit of Aripuanã. Despite its mineral importance, the geological and geochronological knowledge of the area is limited. Different types of deposit have been inaccurately described at the AFGP - e.g. porphyry-, epithermal-, orogenic- or intrusion-related. Part of this difficulty results from the complexe and uncertain classification schemes that were used.

-57º

A

-55º

Juruena Novo Astro

Álvaro Tavares

Papagaio Ico

Zé Vermelho

APIACÁS PARANAÍTA

Trairão

NOVA BANDEIRANTES ALTA FLORESTA

-10º

Rato

Guarantã Ridge

Luizão

S. Guarantã

Aripuanã Zn-Pb-(Cu)

X1 Peteca Paraíba

MATUPÁ P. AZEVEDO

Pé Quente Fabinho/Gil Francisco

Tapajós

0

30

60km

COLÍDER

-59º

-58º

< 1.6 Ga Granites and gabbros 1.75-1.70 Ga Volcano-plutonic associa on 1.81-1.75 Ga 1.82-1.77 Ga

Sedimentary rocks K-feldspar-rich granitoids Acidic volcanic rocks Isotropic granitoids Deformed granitoids

-57º

1.82-1.77 Ga 1.81-1.79 Ga ~ 1.87 Ga > 1.95 Ga

-56º

-55º

Tectonic and Structures

Metabasic rocks High-grade metamorphic rocks

Structures interpreted from surface and subsurface data Normal fault Mineral deposits

Monzogranite and monzonite Gabbro and diorite Orthogneissic and grani c basement

58°0'0'’

Ac ve ar sanal mines Deac vated ar sanal mines Towns

56°0'0'’

B

Geophysical Lineament Gold Deposits Occurrences Gold 0

City

Paranaíta

10°0'0'’

Nova Bandeirantes Alta Floresta Matupá

Colíder

Figure 01 - (A) Simplified geological map of the Juruena-Teles Pires project area. (B) Geophysical lineament interpretation surimposed on the principal gold occurrences and deposits.

30

30

60km


The Juruena-Teles Pires Mineral Province (JTPMP) is located at the southern margin of the Amazonian Craton. This region experienced three main magmatic events that include: (1) 1.99-1.93 Ga granitic and metamorphic basement composed of felsic intrusions and highly deformed metamorphic rocks; (2) ca. 1.87 Ga granitic and basaltic magmatism; and (3) 1.82-1.70 Ga felsic and mafic volcanic-plutonic magmatism (Figure 02). During this third event a high-grade metamorphic core complex that comprises metasedimentary and meta-igneous units (upper amphibolite to granulite facies) also formed (Figure 03). The Beneficent Group (1.5-1.4 Ga) overlies all the above described units and is characterized by a rift-related sedimentary sequence composed of arenite and pelite intruded by mafic and felsic rocks.

(ignimbrite, tuff). Compiled U-Pb ages from the Colíder Group indicate a magmatic activity concentrated between 1.82-1.77 Ga. Sm-Nd isotopic data indicates model ages ranging between 2.8-1.8 Ga with ƐNd(t) between +5.45 and -3.06, indicative of anheterogeneous magmatic source with contribution of both the mantle and the crust. The Teles Pires Suite is composed of alkali-feldspar granite, syenogranite, monzogranite, monzonite and granophyre, showing mixing textures such as rapakivi, fine-grained mafic and felsic enclaves. U-Pb crystallization ages range between 1.81-1.75 Ga while Sm-Nd model ages between 2.4-1.94 Ga, with ƐNd(t) between +3.0 and - 3.4, suggesting the same conditions of formation as for the Colíder Group. Assis (2015) dated the mineralization in three gold deposits located in the eastern part of JTPMP : (1) Pé Quente (Re-Os in pyrite) -- 1.792 ± 9 Ma to 1.784 ± 11 Ma; (2) Luizão (Re-Os in pyrite) -- 1.790 ± 9 Ma to 1.782 ± 9 Ma; and (3) X1 (Re-Os in molybdenite) -1.787 ± 7 Ma to 1.785 ± 5 Ma. The yielded isochron

The Colíder Group was formed during an acidic volcanic event of high-K, calc-alkaline, meta- to peraluminous compositions and mainly comprising rhyolite, dacite, andesite and pyroclastic rocks

10

Juruena Suite (1.82-1.75 Ga) Syenogranite, bt monzogranite, foliated granite, porfiri c bt monzogranite

2

206

Pb/238U

Number

5. Teles Pires Suite (1.81-1.75 Ga) Alcali-feldspar granite to granodiorite, monzonite and monzodiorite

8

0.34 1800 1700

Intercepts at 72 - 130 & 1818-6 [-9]Ma MSWD = 1.2

1600 0.26

6

0.22 3.5

4.5

207

Pb/235U

5.5

6.5

7.5

2640 2

1957

0

1500

1700

1900

2100

2300

2500

2700

2900

Idade 207Pb / 206Pb U-Pb data of zircon from sedimentary-derived migmatite. The migmatization age is indicated by the upper intercept of 1818 Ma, constructed with analysis of spots located on rims.

3. Flor da Serra Suite Gabbro, monzogabbro and diabase 2. Matupá Suite (1.87 Ga) Mozonite and granodiorite syenogranite and monzogranite

0.35

1800

U

1600 1400

0.25

1200 1000

0.15

1

2000 1900

0.30

206

2.00-1.93 Ga Orthogneissic and grani c basement

2100

0.38

4

Nova Monte Verde Complex Orthoderived Unit (1.80-1.78 Ga) Tonali c/granodiori c migma te Paraderived Unit (1.81 Ga) aluminous migma te

3

TL-14 Leucossome

0.46

0.42

4. Vespor Suite (1.77-1.76 Ga) Gabbro and amphibolite

4

1876

Pb /

~1.87 Ga Grani c and basal c magma sm

Colider Group (1.82-1.77 Ga) Riolite, dacite, ignimbrite and epiclas c rocks

238

1.82-1.70 Ga Rondônia-Juruena Province. High-grade metamorphic rocks, felsic magma sm and sedimenta on

12

Relative probability

5

data-point error ellipses are 68.3% conf.

Beneficente Group (1.75-1.70 Ga) Arenite, sil te, argilite and limestone

1. Nhandu Suite (1.99-1.93 Ga) Syenogranite, monzogranite and granodiorite

800

Intercepts at 20±42 & 1763±6 [±8]Ma MSWD = 2.7

600

0.05

Cuiú-Cuiú Complex (2.00 Ga) Granodiori c orthogneiss and migma c tonalites

0.5

1.5

2.5

3.5

4.5

5.5

Paleossome age of the Monte Verde complex Figure 03 - Combined histogram and probability density diagram (upper panel) with the corresponding concordia (lower panel) of U-Pb zircon ages obtained from leucosome, with the upper intercept interpreted as the age of migmatization.

Figure 02 - Schematic representation of the JTPMP units with the different types of intrusions involved.

31


age of 1.786 ± 1 Ma was interpreted as the age of a single mineralizing event for these three gold deposits (Assis, 2015). Those results corroborate with the ages obtained from porphyritic granite bodies (União do Norte porphyry: Miguel-Jr, 2011; Assis, 2015), which have been interpreted as the source of the mineralizing agent. Some authors do not discard the possibility of more than one mineralizing event at JTPMP. This province is considered as the counterpart of the Tapajós Mineral Province, located to the north and separated by the Cachimbo graben, and whose isotopic data suggests an age of 1.87 Ga for the mineralizing event.

deposits of Au + Zn + Pb ± Cu. Both deposit types are hosted by granites (Assis, 2015). Serrinha and Juruena deposits have been additionally considered as porphyry type (Abrão) emplaced in a volcanic arc setting. The gold mineralization in the province occurs along transtensional faults and ductile-brittle shear zones (Figure 01). Most of the deposits are hosted in quartz veins and veinlets cutting granite bodies and volcanic rocks. The shapes of the orebodies are variable but predominate as pyrite, chalcopyrite and/or galena-bearing quartz veins, with gold concentrated in dilatational fault jogs or transtensional faults (Figures 04 and 05). Most of the veins are up to 3 m thick and several tens of meters long (e.g. Paraíba deposit -in the Peixoto de Azevedo region). The mineralization also occurs as disseminated sulfides within the hydrothermal alteration zones of volcanic and granitic rocks (Figure 06). The hydrothermal alterations associated with mineralization are mainly phyllic and containsericite, quartz and pyrite. The more distal of these alterations are represented by propylitic

The main characteristics of gold mineralization in the Alta Floresta region are the same as in the Tapajós area and only differ by slightly younger ages. There are two main types of gold mineralization in the Alta Floresta area: (1) Small disseminated and structurally-controlled deposits of Au ± Cu - (Bi, Te, Ag, Mo), associated with pervasive silicification and sulfidation; and (2) Structurally-controlled vein-type

A

N10°E/80°SW Crentes

N55°E/60°SE D.Maria

E

W

C

B

N σ1

D

E

σ1 ~ N-S

σ3 σ3

T σ1 Figure 04 - (A) Structural model of the shear zone identified in the Crentes and Dona Maria deposits. (B) (C) (E) Shear zone filled by quartz and sulfide and extensional veins filled by drusiform quartz. (D) Riedel scheme showing σ1 and σ3 vector directions.

32


Veins

Tension Gashes

s1 ~N-S

° N50

E

0°S

E/8

Tension Gashes

s1

Figure 05 - Geometric interpretation of the shear zone identified in the Cajueiro Project. Tension gashes with N-S direction, filled by quartz and kaolin, and formed in a sinistral shear zone (σ1 = NNE-SSW).

haloes with epidote and chlorite. Potassic alterations (K-feldspar) are mainly barren zones. The Au-bearing quartz veins contain CO2-rich fluid inclusions with <25% NaCl, with spiky high gold hosted by pyrite- and carbonate-rich phyllic alteration. The disseminated gold mineralization in the Alta Floresta region is spatially and genetically related to acid porphyritic dykes and small plugs. The intrusive rocks have a granophyric texture indicating an emplacement at shallow crustal levels. The conceptual model in Figure 07 shows that the Colíder magmatism, responsible for the gold mineralization, occurred simultaneously with the neosome formation of the migmatites, corroborating its intraplate signature (Rizzotto et al., 2016). This is in accordance with the previous proposal made by Teixeira et al. (2015) on the origin of the gold mineralization in the AFGP.

33

Copper and base metals occurrences are also present in the province. One of the most famous deposits is Aripuanã, which consists of a Zn-Pb-AgCu-Au deposit hosted by felsic volcanic rocks of Roosevelt Group - i.e. the counterpart of the Colíder Group and located southward. This deposit is being developed by Votorantim Metais and with a real potential for new discoveries in the region. Another known Pb-Zn deposit with gold is the Francisco deposit, nearby the União do Norte village in the region of Peixoto de Azevedo. There is also an exploration target for base metals named “Guarantã Ridge” that is in the preliminary study phase. At this target (Serrinha de Guarantã), although no viable copper deposits have been discovered until now, a drill hole previously explored by Rio Novo Gold intercepted a 45 m long section with 0.5% Cu.


A

B

C

D

E

F

Figure 06 - Exposure and hand specimen from the Peixoto de Azevedo gold district. (A) Banded quartz vein with quartz bands alterna ng with chlorite and sulfides bands, as exposed at Serrinha do Gurantã gold deposit sha . (B) Free gold in rusty sulfide-rich quartz vein from Valen m deposit. (C) Quartz vein with chlorite and pyrite bands. (D) Vein samples from Serrinha do Gurantã deposit with copper-rich sulfides (bornite and chalcocite) and secondary copper minerals (malachite, azurite and chrysocolla). (E) Cut sample of granite from X1 deposit with phyllic altera on and disseminated pyrite (blue circles). (F) Hand specimen of hydrothermal breccia from Gurantã Ridge deposit, with venules filled by galena and disseminated chalcopyrite.

34


Francisco e Bigode

Phyllic

Gold Disseminated Pé Quente Serrinha X1

Paraiba

Alta Floresta

A

Mineralization 1.78 Ga Assis (2015)

B 1760 -1750 Ma 1813 - 1763 Ma

Sintectonic Granites

1810 - 1780 Ma

1813-1763 Ma

Dikes Neossome

Migma tes / Granulites Paleosome MASH

MASH

1818-1763 Ma

C

Adapted from Rizzo o et al., 2016

Figure 07 - (A) Schema c representa on of the Alta Floresta gold deposits, including: (1) Disseminated gold in phyllic altera on zones, associated with acid subvolcanic dykes and plugs; (2) Massive quartz veins and stockworks with epizonal to mesozonal tectonic fabrics and restricted wall-rock altera on (adularia, sericite, K-feldspar, chlorite); and (3) Spa al and temporal associa on with post-tectonic granites. Note that the União do Norte, X1, Pé Quente gold deposits are related to phorphyry rocks and phyllic altera on zones. (B) Hand specimen of vuggy quartz vein. (C) Schema c model showing extensional environment and underpla ng development as causes for genera ng felsic magmas (1.82-1.70 Ga). The ages of neosomes in migma tes coincide with the ages of the volcanic and subvolcanic rocks (1.82-1.77 Ga) related to the gold mineraliza on (1.78 Ga). Fluids responsible for the gold and polymetallic deposits of the Alta Floresta were exsolved from underplate magmas at a ri ed cratonic margin, and probably derived more from mantle upwelling than slab subduc on.

References: ASSIS, R.R., 2015. Depósitos auríferos associados ao magmatismo félsico da Provincia de Alta Floresta (MT), Craton Amazonico: Litogeoquímica, idade das mineralizações e fonte dos fluidos. Tese de Doutorado. Instituto de Geociências, Universidade de Campinas, Campinas, 363 p. MIGUEL-JR, E., 2011. Controle estrutural das mineralizações auríferas e idades U-Pb das rochas encaixantes ao longo do Lineamento Peru-Trairão: Província Aurífera de Alta Floresta, Mato Grosso. Dissertação de Mestrado. Instituto de Geociências, Universidade de Campinas, Campinas. MOURA, M.A., 1998. O maciço granítico Matupá e os depósitos de ouro Serrinha (MT): petrologia, alteração hidrotermal e metalogenia. Tese de Doutorado. Brasília, UnB, 238 p.

35

MOURA, M.A., BOTELHO, N.F., 2002. Petrologia do magmatismo associado a mineralização do tipo ouro pórfiro da província aurífera Juruena-Teles Pires (MT). Revista Brasileira de Geociências, v. 32, n. 3, p. 377-386. RIZZOTTO, G.J., 2016. Significado Tectônico das rochas de alto grau do norte do Mato Grosso. In: CONGRESSO BRASILEIRO DE GEOLOGIA, 48, 2016, Porto Alegre - RS. Anais. São Paulo - SP: Sociedade Brasileira de Geologia. XAVIER, R.P., ASSIS, R.R., CREASER, R., TREVISAN, V.G., PAES DE BARROS, A.J., AZEVEDO, A., MIGUEL-JR, E., BARROS, M.A.S., PINHO, F.E.C., 2013. Timing of gold metallogeny in the Alta Floresta Gold Province: evidence from pyrite and molybdenite Re-Os isotopic dating. In: 13° Simpósio de Geologia da Amazônia, 2013, Belém (PA).


Seridó Project

Alan P.da Costa, Alexandre R. Dantas, André L.C. da Cunha, André L. Spisila, Rogério Cavalcante, Rafael B. Lima

The Seridó Project is being developed by the Geological Survey of Brazil (CPRM) as part of its programs “Geological Geophysical Integra on and Predic ve Prospec vity Mapping of the Brasilian Shields” (Program I) and “Mineral Poten al Assessment of the Brazilian Volcano-Sedimentary Sequences” (Program III). The Borborema Province is a poly-deformed Neoproterozoic Brasiliano/PanAfrican belt in northeastern Brazil that covers a total area of over 450,000 km2. It is located to the north of the Archean-Paleoproterozoic São Francisco Craton. Its architecture results from a diachronic collage of Archean nuclei, Paleoproterozoic terranes and

Tonian-Ediacaran belts during the closure of western Gondwana. It is enclosed between São Luis/West African and São Francisco/Congo cratons (Brito Neves et al., 2000), and distributed in five large domains or terranes (Médio-Coreau, Ceará Central, Rio Grande do Norte, Zona Transversal and Meridional) that are separated by deep transcurrent shear zones (Transbrasiliano, Senador Pompeu, Patos and Pernambuco). An Archean/ Paleoproterozoic basement is recognized to the north of the Patos shear zone while TonianEdiacaran belts predominate in the Transversal and Southern domains. 36oW

38oW

Potiguar Basin

2

0

300

Natal

o

6S

2000

JD

1000

JCD

3

200

PSD

João Pessoa

1

ZTD

? o

?

?

8S

Recife

4 PAD Modified from Medeiros (2011)

LEGEND

Transcurrent Shear Zones Phanerozoic Cover Depth (meters) Brasiliano Granitoids 1) Patos 2) Picuí-João Câmara, City JD - Jaguaribeano Domain 3) Portalegre 4) Pernambuco PSD - Rio Piranhas-Seridó Domain Project Area JCD - São José do Campestre Domain 0 25 ZTD - Zona Transversal Domain PAD - Pernambuco-Alagoas Domain Figure 01 - Loca on of the Seridó Mineral Province within the geological and metalogene c Borborema Province (adapted from Medeiros et al., 2011).

36

50km


The Seridó Mineral Province (SMP) is part of the Rio Piranhas-Seridó subprovince (PSD) of the Rio Grande do Norte Domain (Figure 01). It hosts historical tungsten mines back to the 1940´s, some s ll in produc on, and more recent gold and iron ore mines. It has a great diversity of mineral deposits (Au, W, Fe, Nb, Ta, Mo, kaolim) and gemstones that were mostly explored by ar sanal prospectors and small-cap mining companies. The Geological Survey of Brazil (CPRM) is currently developping the Seridó Project aims at providing a geological-geophysical integra on map of the SMP and a semi-regional geochemical survey on fi een 1:100,000 sheets. Also as part of this project the metavolcano-sedimentary Jucurutu Forma on, hos ng most of the W and Fe occurrences in the province, is being mapped at 1:50,000 scale, including detailed studies of the main mineral deposits (W: Brejuí and Bodó; Au: São Francisco, Bonfim; Fe: Saquinho). Figure 01 shows the coverage of the fi een sheets mapped at 1:100,000 scale by the Geological Survey of Brazil (CPRM) and that encompass the Seridó Mineral Province. The western Jaguaribeano Domain (JD) and the eastern São José do Campestre Domain (JCD) are bordered by the Portalegre (3) and Picuí-João Câmara (2) shear zones respec vely, with the central Rio Piranhas-Seridó Domain (PSD) between. The southern Zona Transversal Domain (ZTD) is delimited by the Patos (1) and Pernambuco (4) shear zones. The São José do Campestre Domain (JCD) remains poorly explored and is characterized by a smooth relief and scarce outcrops. It has preserved a Paleoto-Neoarchean block (Núcleo Bom Jesus-Presidente Juscelino: Bizzi et al., 2001), which is surrounded by agglu nated Palaeoproterozoic migma zed units (Santa Cruz Complex). Entangled metaplutonic s u i t e s w i t h T TG ( t o n a l i t e - t r o n d h j e m i t e granodiorite) affinity, and some scarce and discon nuous metavolcanic and Algoma-type BIF are reported. The Rio Piranhas-Seridó Domain (PSD) is composed of a Siderian-Rhyacian-Orosirian basement (Arabia and Caicó complexes) with scarce Archean relics and supracrustals rocks of the Ediacaran Seridó Group. The Arabia complex mainly comprises ortho-derived metaplutonic units, whereas the Caicó complex is a heterogeneous, polydeformed and widely migma zed gneiss with metavolcano sedimentary

37

and metaplutonic protholites. Recent geophysical survey and field inves ga on have iden fied kimberlite intrusions hosted by the Arabia complex in the northwest of Lages city, Rio Grande do Norte State (Cabral Neto et al., 2015). The Seridó Group consists of low-to-medium grade metasediments, with the basal Jucurutu Forma on locally composed of discon nuous volcanosedimentary sequences that include the mineralized BIF of Saquinho Fe mine. The Jucurutu Forma on is overlaid by a carbonate pla orm and siliciclas c rocks of the Equador Forma on, both being overlapped by the turbidite-flyschoid sequence of the upper and extensive Seridó Forma on. Plutonism related to the Brasiliano Event (Ediacaran age) intrudes all the Seridó units. Its main phase was dated between 580-550 Ma and is represented by the extensive porphyri c high-K calc-alkaline Itaporanga suite and other minor plutonic rocks. Isotropic grani c bodies of non-determined chemistry and late orogenic pegma c dykes were dated between 514-509 Ma. The most significa ve W occurrences at SMP are charaterized on the airborne magne c maps (Figure 02) by shallow anomalies that coincide with nega ve gravimetric anomalies. These anomalies are interpreted to represent a series of structurally controlled grani c intrusions (Itaporanga suite), whose the interac on with the metasedimentary Seridó Group forma ons formed rheological and chemical interfaces favorable to W concentra on. The gamma-spectrometric survey (Figure 03) iden fied strong potassium anomalies correlated with the major W deposits, and a discon nuous potassium anomaly along the second-order structure of São Francisco shear zone and where is located a gold deposit. The Saquinho Fe deposit is correlated to posi ve gravimetric and magne c anomalies. More than 700 skarn occurrences are listed in SMP, with some that were intermi ently explored since the 1940's for W-Mo (Brejuí, Bodó, Bonito, Malhada Limpa and Quixadá mines), gold (Itajuba ba mine), and gold associated with W-Mo-Bi-Te (Bonfim mine). The main deposits are Brejuí and Bodó that respec vely contain 11 Mt of WO3 (with 5.5 Mt remaining at 0.5-1.0% WO3) and 9 Mt at 2% of WO3. Iron deposits also occur as magne te-hema te bearing deposits, with grades commonly around 43% Fe and up to 60% Fe, with the major body


36°45'W

36°15'W

35°45'W

5°45'S

37°15'W

37°45'W

Au-W

Fe

6°15'S

W Au Fe

7°15'S

6°45'S

W

0

20

Mineral deposits

40km

Figure 02 - Reduced-to-pole (RTP) magnetic map of the Seridó project area showing magnetic alignments, mainly orientated between azimuths 90°and 45° and, to a lesser extent, between azimuths 270° and 290°. 36°45'W

36°15'W

35°45'W

5°45'S

37°15'W

37°45'W

Au-W

Fe

6°15'S

W Au Fe

6°45'S

W

7°15'S

Mineral deposits

0

20

40km

Figure 03 - Ternary gamma-spectrometry map (K, eU, eTh) of the Seridó project area. The high-K contents are mainly related to granitic intrusions and Neoproterozoic pegmatites that host gemstones, kaolin and wolframite mineralizations.

38


(Saquinho iron mine) containing 38 Mt at 55% Fe (Santos et al., 2014).

ounces of gold (Aura Minerals on-line report, 2011). The tungsten (W) deposits are spa ally related to the Itaporanga high-K calc-alkaline suite that shows an extensive skarnifica on along the contact between rocks with constras ng rheologies. The main mineralized bodies occur interstra fied in the marble lenses of the Jucurutu Forma on (Figure 04). Skarnifica on is also present as endoskarn within the granite (e.g. in the Bodó and Itajuba ba mines) and at the contact with the basal shear zone with the Caicó complex. Polymetallic sulfides are also reported but their poten al remains unexplored.

The mineralogy of the gold deposits comprises sulfides and oxides, with a paragene c associa on of pyrite-chalcopyrite, pyrrho te, magne te and ilmenite. Galena, Ag-arsenopyrite and molybdenite were also reported in the São Francisco deposit. Gold grades are usually in the range of 1-5 g/t up to 30 g/t. Based on a cut-off grade of 0.25 g/t Au, the total reserves are expected to edge up to 10,890 tons at 0.91 g/t Au, corresponding to about 318 FBM-05 FBM-08 550

BDM-04

Altitude (m)

BDM-03

500

450

400

LEGEND Soil Pegmatites Calc-silicates rocks Biotite granite

Foliation

Granite alteration halo Jucurutu Fm.: (a) Magnetite bearing biotite gneiss

BDM-03

Drillholes

+

(b) Marble lenses

0

25

50m

Horizontal Scale

Figure 04 - Ver cal E-W cross-sec on 01 of the Bodó tungsten mine, with drill holes FBM-05, FBM-08, BDM-04 and BDM-03.

The ore deposits show evidence of hightemperature calcic altera on (up to 650°C) forming anhydrous calc-silicates (diopside, andradite, wollastonite). Medium-temperature altera on followed with the forma on of hydrated silicates (hornblende, vesuvianite, escapolite, epidote, ac nolite, grunerite), scheelite and disseminated sulfides. Carbonate veins and cavi es filled with sericite, zeolite, limonite and powdery scheelite, indicate altera on by fluids of progressively decreasing temperature (Figure 05). The banded iron forma on from Saquinho, Serra da Formiga, Bonito, Serra do Fei ceiro, Riacho Fundo and Serra dos Quintos occur associated with mafic volcanics at the base of the Jucurutu Forma on (Figure 06). The BIF are anomalous in Cr, Ce, REE and Eu, confirming a volcanic influence on its genesis (Algoma-type), whereas stable and radiogenic

39

isotopes (nega ve δ13C and 87Sr/86Sr) suggest a glacial influence (Sial et al., 2015). The gold deposits of São Francisco, Simpa co, Ponta da Serra, São Fernando and Bonfim, are lode-gold deposits related to high-angle shear zones cu ng Neoproterozoic (Seridó Group) and Palaeoproterozoic rocks (basement gneisses), and that were ac ve during a late deforma on event dated between 520-500 Ma. This age obtained from 40 Ar/39Ar da ng of mica (Araújo, 2001) is similar to other orogenic-gold age models. The basement of Bonfim gold deposit, located to the north of the São Francisco fault, yields an Archean age (3.508 Ma) based on U-Pb zircon da ng (Velásquez et al., 2016). This suggests that Archean inliers below the São Francisco shear zone may have contributed to the gold mineraliza on.


Brejui Mine - Epidote-diopside skarn cross-cu ed by molybdenite veinlet associated with par ally filled cavity with carbonate, zeolite, limonite and powdery scheelite Mineral abbrevia ons according to Whitney & Evans, 2010: Sch - Scheelite, Zeo - Zeolite, Cb - Carbonate, Mol - Molybdenite

Bodó Mine - High grade ore. Scheelite bearing veins and disseminated scheelite in epidote-diopside skarn. Scale: 15x23 cm. Mineral abbrevia ons according to Whitney & Evans, 2010: Sch - Scheelite, Di - Diopside, Ep - Epidote, Grt - Garnet, Ves - Vesuvianite

Figure 05 - Rock exposures with tungsten ore at the Bodó and Brejuí mines.

Schematic Section (around 580-520My)

Paleo -proterozoic

Neo -proterozoic

Schematic Stratigraphy

Brasiliano Plutonics (590 - 540 Ma) Granitoids Jucurutu Fm. (630 - 600Ma) Biotite (amphibole) paragneiss partially epidotized Banded Iron Formation (Rapitan type ?) Amphibole-biotite schist with garnet Marble Banded Iron Formation interlayered with garnet amphibolite Rhyacian Augen Gneiss (2.171 Ma)

Archean

Deformed supracrustals Amphibole-Biotite augen gneiss Archean (2.512 Ma) Banded Iron Formation (Algoma type) Metaultramafic with mafic subordinated Chlorite-biotite schist interlayered with quartz-feldspar mylonite Felsic mylonitic gneiss (some volcanogenic?) Amphibole-Biotite mylonitic tonalitic gneiss

Figure 06 - Schema c cross-sec on at around 580-520 Ma and stra graphic column of the basal units of the Jucurutu Forma on.

References ARAÚJO, M.N.C., 2001. A cinemática superposta e as mineralizações auríferas da Faixa Seridó: uma abordagem meso e microscópica. Tese de Doutorado, IG/UFRN, 256 p; Aura Minerals report 2011, available in: http://www.auraminerals.com/ Operations/SaoFrancisco/Reserves-and-Resources/default.aspx. Date of access 02/10/2017. BIZZI, L.A., SCHOBBENHAUS, C., GONÇALVES, J.H., BAARS, F.J., DELGADO, I.M., ABRAM, M.B., LEÃO NETO, R., MATOS, G.M.M., SANTOS, J.O.S., 2001. Geologia, Tectônica e Recursos Minerais do Brasil. Sistema de Informações Geográficas - SIG e mapas na escala de 1:250.000.000. CPRM, Editora da Universidade de Brasília, Brasília, CD-ROM. BRITO NEVES, B.B., SANTOS, E.J., VAN SCHMUS, W.R., 2000. Tectonic history of the Borborema Province, Northeastern Brazil. In: CORDANI, U., MILANI, E., THOMAZ FILHO, A., CAMPOS, D.A. (Eds.) Tectonic Evolution of South America. Special Publication, 31st International Geological Congress, Rio de Janeiro, Brazil, p. 151-182. CABRAL NETO, I., CUNHA, L.M., SILVEIRA, F.V., OLIVEIRA, R.G., SOUZA, W.S., BEZERRA, A.K., 2015. Registro dos primeiros corpos com afinidade kimberlítica na Província Borborema, NE do Brasil. Informe Técnico N2.

MEDEIROS, V.C., MEDEIROS, W.E., JARDIM DE SÁ, E.F., 2011. Utilização de imagens aerogamaespectrométricas, landsat 7 ETM + e aeromagnéticas no estudo do arcabouço crustal da porção central do domínio da zona transversal, província Borborema, NE do Brasil. Revista Brasileira de Geofísica, v. 29, p. 83--97. SIAL, A.N., CAMPOS, M.S., GAUCHER, C., FREI, R., FERREIRA, V.P., NASCIMENTO, R.C., PIMENTEL, M.M., PEREIRA, N.S., RODLER, A., 2015. Algoma-type Neoproterozoic BIFs and related marbles in the Seridó Belt (NE Brazil): REE, C, O and Sr isotope evidence. Journal of South American Earth Sciences, v. 61, p. 33-52. SANTOS, J.E., SOUZA NETO, J.A., SILVA, M.R.R., BEURLEN, H., CAVALCANTI, J.A.D., SILVA, M.G., DIAS, V;M., COSTA, A.F., SANTOS, L.C.M.L., SANTOS, R.B., 2014. Metalogênese das porções norte e central da Província Borborema, in SILVA, M.G., ROCHA NETO, M.B., JOST, H., KUYMJIAN, R.M. (Eds.), CPRM, 2014. VELÁSQUEZ, F., DELLA GIUSTINA, M.E., OLIVEIRA, C.G., DANTAS, E.L., 2016. Lentes ultramáficas paleoarqueanas na faixa Seridó, NE do Brasil: Evidencias de reequilíbrio de óxidos de Fe-Ti-V no Brasiliano. Anais do XLVIII Congresso Brasileiro de Geologia, Porto Alegre, Rio Grande do Sul.

40


NW Ceará Project Tercyo R.G. Pinéo, Alex F. Lima, Mariane D. Martins, Maria D.M.R. Bessa

The Northwest Ceará Project is being developed by the Geological Survey of Brazil (CPRM) as part of its program “Geological Geophysical Integration and Predictive Prospectivity Mapping of the Brazilian Shields” (Program I). The main o b j e c t i v e o f t h i s p ro j e c t i s t o s t u d y t h e metallogenic potential and to identify new

mineral occurrences in the Martinópole Group, a Neoproterozoic meta-volcano-sedimentary sequence which hosts polymetallic Cu-Pb-Zn sulfides, copper, iron ore, manganese and barite mineralizations (Figures 01 and 02). The Granja Complex represents the basement of this supracrustal sequence and is composed of

-41°00'

-40°30'

Granja

Martinopole

1

Uruoca

3°30'

3

2 Vicosa do Ceara

Sobral

Fault

0

10

20km

LITHOSTRATIGRAPHIC UNITS PALEOGENE BARREIRAS GROUP Sandstones, conglomarates and laterites.

Metasandstones (Goiabeira Formation).Gray and blue Metamarbles (Frecheirinha Formation). Slate, phyllite and metasandstone (Caiçaras Formation). Quartzites and metasandstone (Trapiá Formation). MARTINÓPOLE GROUP Phyllites, marbles, quartzites, metacherts, metavulcanics, and BIF’s (Santa Terezinha Formation). Schists, phyllite, and BIF’s (Covão Formation). Quartzites with intercalation of schists, alc-silicate and BIF’s (São Joaquim Formation). Schists, quartzites, and paragneisses (Goiabeira Formation).

SILURIAN SERRA GRANDE GROUP Sandstones, siltites, argillites and conglomarates. CAMBRO-ORDOVICIAN

Conglomarate (Fazenda Fortaleza Formation).Sandstone, siltite and argillites (Morada Nova Formation). Polimitic Conglomerate (Barra do Sairi Formation).

Migmatitic paragneisses with lenses of quartzite, calc-silicate, marble, amphibolite, metavolcanics (700 Ma).

Polimitic Conglomerate (Aprazível Formation).Basalts and rhyolite (Parapuí Formation). Sandstone and siltite intercaleted (Pacujá Formation). Polimitic conglomerate (Massapê Formation). MERUOCA GRANITOIDS Batholiths ans stocks of red granites (532 Ma).

Metarhyolite, metabasalt, BIFs, calc-silicate, and volcanoclastic rocks (1785 Ma). FORQUILHA ORTHOGNEISSE Tonalitic to granodioritic orthogneisses with amphibolite enclaves (2049 Ma).

Brejinho Suite - Syenites and alkaline piroxenites (554 Ma).

Milonitic gneisses, paragneisses, metaultramafic rocks, marbles, amphibolite, and calc-silicate. Granitic to granodioritic orthogneisses intrusive (2100 Ma).

Tucunduba - Green Granite and granodiorite (574 Ma). Chaval Suite - Porfiritic monzogranite, granites, syenites (591 Ma).

Orthogneisses, migmatites, granulite gneisses, leucogneisses, calc-silicate, quartzite, paragneisses and amphibolite (2357 Ma).

Metatexites, diatexites, gneisses and porfiritic pink granites (650 Ma).

Figure 01 - Geological map of the NW Ceará project area.

41


TTG orthogneisses, paragneisses and granulites of Paleoproterozoic age (2.3 Ga) (Santos, 1999). The Martinópole Group is divided in four lithological formations (Figure 03) deposited on a passive continental margin between 800-750 Ma (Santos, 1999), and later deformed by the Brasiliano/Pan-African Orogeny (ca. 600 Ma) and metamorphosed to low- to medium grade (i.e. from greenschist to amphibolite facies) (Figure 04). The Goiabeira Formation at the base of the Martinópole Group consists of schists, quartzites and paragneisses. The São Joaquim Formation is mainly composed of quartzites. The Covão Formation comprises schists and phyllites. The uppermost Santa Terezinha Formationconsists of phyllites, ca r b o n ate p hy l l i te s , m a r b l e s , q u a r t z i te s , metacherts, calc-silicatic rocks, BIFs, and metavolcanic rocks, dated by zircon U-Pb at 800 Ma (crystallization age). This formation hosts deposits and mineral occurrences of copper, lead, zinc, manganese and iron, which are grouped into three separate exploration targets (Uruoca, Pedra Verde Mine and Serra de São José) (Figure 05).

The Uruoca targethas been investigated by the Geological Survey of Brazil (CPRM) during the 1980´s. It is composed of phyllites and quartzites with mylonitic structure, metachert, hydrothermal breccia, meta-rhyodacite, and laterite covers. The metachert contains concentrations of manganeseiron oxide and minor widespread crystals of bornite and pyrite. The hydrothermal breccia has a typical boxwork texture and is distributed along a NE-SW shear zone (Figure 06). The manganese mineralization at Uruoca is related to laterites aligned NE-SW, with hydroxide, iron hydroxide, hematite, magnetite and quartz fragments also arranged in a boxwork texture. The presence of manganese layers and phyllites, both intercalated and folded, suggests a syngenetic occurrence with superimposed weathering processes. Chalcopyrite, pyrite, bornite, sphalerite and galena were described from borehole samples, occurring both in fractures and veins of associated metacarbonate rocks (marbles, carbonatic phyllites, and calc-silicatic rocks) and meta-acidic volcanic rocks (Prado et al., 1980).

-41º

-40º 30'

Martinópole

Uruoca Target

Uruoca

-3º 30' 488 125

Viçosa do Ceará

71

Sobral

nT 33

5

-270

Figure 02 - Reduced-to-pole (RTP) magnetic map showing the distribution of magnetic bodies to depth of 1-2 km, with interpreted structural lineaments marked by black lines.

42


MARTINÓPOLE GROUP

808Ma

Formations BIF’s Calc-silicate

Santa Terezinha

Metafelsic Metacherts

Passive Margin 800 - 750 Ma

Santa Quitéria Arch 660-630 Ma Troiá Massif Ceará Complex Greestone belt Backarc (750 Ma)

Martinopóle Group

Canindé do Ceará Basement

Granja Complex Basement

Phyllite

Covão Continental collision Cu-Co-Ba-BIF 620-615 Ma Zn-Pb Syn-Orogenic Post-Orogenic 590 Ma 520 Ma 3 1 UHP 2

Calc-silicate

Cr-PGE Troia Massif

4 530-480 Ma

São Joaquim

Quartzites

5

7

6

2.1 Ga

480 Ma TTG 3,5-2,7 Ga

Post-Colisional

Paragneisses

Goibeira

Quartzites

2300Ma

1 - Cu-Co Pedra Verde 2 - Cu-Fe Jaíbaras 3 - Au Rerituba

Schists Granja Complex

4 - Fe Santa Quitéria 5 - Ti Independência

6 - Cr-PGE Tróia 7 - Au Pedra Branca

Figure 04 - Geodynamic model of Northwest Ceará including the Martinópole Group, showing the evolution from a passive margin to continental collision between Médio Coreaú and Ceará Central domains (modified from Araujo, 2014).

Figure 03 - Lithostratigraphic column of the Martinópole Group.

Uruoca Region

LITHOSTRATIGRAPHIC UNITS PALEOGENE

Ceará Central Domain

Médio Coreaú Domain

Pedra Verde/Serra de São José Region

Serra Grande Group

Barreiras Group NEOPROTEROZOIC CAMBRO-ORDOVICIAN Riacho Sairi Group

( (

) PALEOPROTEROZOIC

Figura 05 - Geological maps of the exploration targets in NW Ceará.

43

)

Normal fault Syncline Shear zone


Mn+Fe B

A

Figure 06 - Rock exposures from the Uruoca target: (A) Metachert with iron-copper sulfide and concentrations of Fe-Mn oxides. (B) Hydrothermal breccia with manganese, iron and quartz.

During the 1980´s a small copper mine (Pedra Verde Mine) operated in the region. The host rocks are along a NE-SW shear zone that is marked by one staggered magnetic lineament. They consist of altered phyllite progressively replaced by carbonated phyllite. The altered phyllite is 22 m thick and contains malachite and azurite as main

secondary copper minerals (Figure 07). The ore is zoned and marked by chalcocite-bornitechalcopyrite-pyrite-galena-sphalerite (Collins and Loureiro, 1971). The sulfides occur either deformed along the mylonitic foliation of the host carbonated phyllite, or along carbonate veins indicating hydrothermal precipitation (Matos, 2012).

Phyllite carbonated with pyrite in carbonate veins

A

B

Figure 07 - Hand specimen and rock exposure from Pedra Verde mine: (A) Borehole sample of phyllite carbonate with sulfide-rich carbonate veins. (B) Malachite resulting from leaching of phyllite carbonate.

The Serra de São José target contains barite associated with Ni (500 ppm) and Co (500 ppm) anomalies in folded BIFs (Figure 08). Its rock formations comprise marbles, phyllites, schists, metagreywackes, metacherts and BIFs (Prado et al., 1979). Geophysical data indicates the possible continuity of this target underneath the Silurian sediments of the Parnaíba Basin.

followed by hydrothermal mobilization and precipitation along the NE-SW structures, during the Brasiliano/Pan-African Orogeny (ca. 600 Ma).

Field observations and a desktop study indicate the possibility of SEDEX-type deposits that formed on a passive continental margin between 800-750 Ma (Figure 09). This sedimentary event was

44


A

B

Figure 08 - Rock exposures from the Serra de São José target: (A) Outcrop of folded BIF. (B) BIF hand specimen.

Serra de São José Target Fe (BIF), Co-anomaly

sea level

Pedra Verde Mine Pelite Cu, Pb, Zn carbonated

10 km

~ ~ ~ ~ ~. . . . . . . . . .

. . . .. .

Slope and abyssal sediments Ubajara Group Pelites, marbles, psamites Martinópole Group ~ ~ Santa Terezinha Formation: pelites

.

.

.

. .

~ . .

.

~ ~ .

.

. .

~

Pelite carbonated Acid volcanic

. .

. .

.

.

. .

.

Basement

.

Carbonate rock

~.

. . . . . . . . . . . . . . . . . . . . . . . .

~

~ ~

~ .

Uruoca Target Cu, Pb, Zn, Mn, Fe

Covão Formation: pelites São Joaquim Formation: psamites Goabeira Formation: pelites, psamites Granja Complex Orthogneisses, migmatites, granulite gneisses. .. .. . .

Hydrotherma Fluid Flow Metal concentration (chemical Trap)

0

50

100 km

Figure 09 - Geologic conceptual model for SEDEX deposits (modified from Emsbo, 2009).

References: ARAUJO, C.E.G., 2014. Evolução tectônica da margem ativa Neoproterozoica do Orógeno Gondwana Oeste na Província Borborema (NE-Brasil). Tese de Doutorado. Universidade de São Paulo. USP. EMSBO, P., 2009. Geologic criteria for the assessment of sedimentary exhalative (sedex) Zn-Pb-Ag deposits: U.S. Geological Survey Open-File Report 2009-1209, 21 p. COLLINS, J.J., LOUREIRO, A.R., 1971. A Metamorphosed Desposit of Precambrian Supergene Copper. Economic Geology, v. 66, p. 192-199. MATOS, J.H.S.N., 2012. Evolução Metalogenética da Mina de Cobre Pedra Verde (CE). 107p. Dissertação (Mestrado em Geologia e Recursos Naturais) -Instituto de Geociências, Universidade Estadual de Campinas, São Paulo.

45

PRADO, F.S., MENDONÇA, J.C.G.S., MORAIS, J.B.A., MEDEITOS, M.F., ASSUNÇÃO, P.R., ANDRADE, V.A., MEDEIROS, R.P., 1979. Projeto Martinópole. Relatório Final. Volume I. Companhia de Pesquisa de Recursos Minerais - CPRM. PRADO, F.S., SCHEID, C., SILVA, S.M.P., MEDEIROS, M.F., MELO, F., 1980. Projeto Uruoca: Relatório preliminar de pesquisa de cobre, chumbo e zinco nos municípios de Uruoca, Martinópole, Marco e Senador Sá - Estado do Ceará. Volume I, Texto e Mapas geológicos. Companhia de Pesquisa de Recursos Minerais - CPRM. SANTOS, T.J.S., 1999. Evolução tectônica e geocronológica do extremo nordeste da Província Borborema. Tese de Doutorado. Instituto de Geociências e ciências exatas. UNESP.


Gurupi Project Leandro D. Campos, Sulsiene M. de Souza, Diogo A. de Sordi, Felipe M. Tavares, Evandro L. Klein, Elem C.d.S. Lopes

The Gurupi Project is being developed by the Geological Survey of Brazil (CPRM) as part of its program “Geological Geophysical Integra on and Predic ve Prospec vity Mapping of the Brasilian Shields” (Program I). The project area sits on the borders of Pará and Maranhão states in northnortheast Brazil. The area is regionally divided into two geotectonic compartments that evolved 46°30'0"W

46°15'0"W

1°45'0"S

1°45'0"S

46°45'0"W

during specific cycles, including the São Luís cratonic fragment (2695-2078 Ma) to the eastnortheast and the Gurupi orogenic belt (980-591 Ma) to the west (Klein et al., 2014). The Gurupi Belt comprises Neoproterozoic sedimentary and intrusive igneous rocks. Its evolu on is related to the breakup of western Gondwana and further tectonic inversion from passive to ac ve margin

Cachoeira do Piriá Boa Vista do Gurupi

2°0'0"S

2°0'0"S

1

L E G E N D Age (Ma)

2116-2078

2167-2148

2695

2

2°15'0"S

2°15'0"S

Phanerozoic Cover Neoproterozoic-Cambrian passive margin, orogeny and continental rift 591 Piriá Formation 624 Metamicrotonalite 980 Gurupi Group Syn-, late- and post-tectonic plutonic suites Biotite-muscovite granite, leucogranite and high-K granite Greenstone belt

3 Mafic metavolcanic, volcanoclastic and Iron formation Muscovite-quartz schist and quartzites Pre-tectonic plutonic suites Amphibolite Granite Gabbro, tonalite and granodiorite Orthognaisses and migmatites Basement Complex Igarapé Grande Metatonalite 46°45'0"W

0

4

4

8 km

5 46°30'0"W

Figure 01 - Geological map of Gurupi orogen and Chega-Tudo greenstone belt (adapted from Klein et al., 2014).

46

46°15'0"W


during mid- to late Neoproterozoic. Most of the Neoproterozoic rocks are thought to be buried under the Paleozoic Parnaiba Basin (Figure 01). In the project area the Gurupi Belt is represented by metasediments of the Gurupi Group, the metamorphosed Caramujinho microtonalite and the Piriá Forma on. The Gurupi Orogeny affected the borders of the cratonic basement during the late Neoproterozoic and was responsible for lowgrade metamorphism, local hea ng and possibly minor gold remobiliza on. Paleoproterozoic Island Arc (2240 - 2050 Ma)

The São Luis cratonic fragment represents an extension of the West Africa Craton that remained in South America a er the opening of the South Atlan c Ocean. It comprises Paleoproterozoic volcanic-sedimentary sequences (greenstone belt) and plutonic suites developed in an island-arc system (Figure 02). The main rock forma ons of this cratonic fragment include: (1) Ultramafic rocks intercalated with carbonated-talc schists, mafic and felsic rocks (2160-2148 Ma), as well as volcanoclas c rocks from the Chega Tudo

Ocean Floor and Volcanic Arc

Parnaiba Block

São Luís West African Craton

Sta. Luzia do Pará Fm.

Peridotites,basalts, andesites, rhyolites and vulcanoclastics

Tromaí Suíte 2168 - 2148 Ma: tonalites, granodiorites e granites

Paleoproterozoic Arc Collision (2100 - 2080 Ma)

Orogenic Gold (Ashanti Type) Igarapé de Areia Fm.

Chega Tudo Fm. Parnaiba Block

São Luís West African Craton 2,69 Ga Tonalite 2,59 Ma Post-collisional Timbozal granite (2084 Ma)

Neoproterozoic Passive Margin (c. 980 Ma) Parnaiba Block

Negra Velha Suite 2056-2076 Ma

Sedimentary Phosfate

Sin-collisional Japiim granites (2100 Ma)

Gold Mineralization Aurizona

Tentugal Shear Zone Cipoeiro Fault

Gurupi Group and Cabeça de Porco Fm.

2240 Ma 2168-2148 Ma

Carbonic aqueous fluids of low to moderate salinity and deep origen (Klein et al., 2014)

Chega Tudo (Greenstone belt)

Neoproterozoic Orogeny (624 - 549 Ma)

32 Ton Au

Cipoeiro 52 Ton Au

Aurizona

65 Ton Au

< 1.140 Ma

Qz gold Veins

Au-Bi-As-Sb-Te

Sienite 732 Ma Nei Peixoto granite 549 Ma

Mineralitation´s age 1879-2000 Ma? Caramugim Metatonalite 624 Ma

Cloritization,carbonatatization, silicificationand sulphidation and graphite

kimberlites 340-370 C

Figure 02 - Reconstructed evolution of the Gurupi orogen, from a passive continental margin to an island arc system marked by volcano-sedimentary sequences. The gold mineralization is restricted to the Chega-Tudo greenstone belt, within sulfide-graphitic quartz veins occurring in brittle-ductile shear zones.

47


Forma on; (2) Muscovite-quartz schists and quartzites from the Santa Luzia do Pará Forma on; and (3) Clast-supported conglomerates and quartzites (<2078 Ma) from the Igarapé de Area Forma on. These sequences were intruded by syntectonic bio te-muscovite leucogranites and post-tectonic high-K granites (2116-2078 Ma). During the same Rhyacian period, basin inversion (with collision?) and metamorphism of amphibolite to upper-greenschist facies released fluids that contributed to the extrac on, transport and deposi on of metals, resul ng in an orogenic gold system hosted in the Chega Tudo and Igarapé de Areia forma ons. Chega Tudo, Santa Luzia do Pará and Igarapé de Areia forma ons, in addi on to the Rhyacian plutonic suites and Archean basement, compose the South American counterpart of the West Africa Craton (e.g. Ashan Belt of Birimian age). Chega Tudo and Igarapé de Areia forma ons can therefore be compared with their African analogues (Ashan Belt, Sefwi and Tarkwan group), which host major gold deposits with a total gold endowment of ca. 125 MOz.

Figure 03 - Analy c signal map of the Gurupi project area.

2°0'0"S

2°0'0"S

The gold mineraliza on is exclusively hosted by the Rhyacian volcanic-sedimentary sequences and pretectonic plutonic suites. It occurs in disseminated sulfides, quartz-sulfide crack-seal shear veins, and quartz stockwork zones related to bri le-duc le

deforma on. The hydrothermal altera ons are composed of quartz, chlorite, sericite, carbonate, a l b i t e a n d s u l fi d e m i n e ra l s ( e . g . p y r i t e , a rs e n o py r i te a n d ra re c h a l co py r i te ) . T h e mineraliza on is concentrated along the Tentugal shear zone and its subsidiary branches. This shear zone is delimited to the west and east by the Chega Tudo and Cipoeiro faults, respec vely. The majority of the gold occurrences and deposits are aligned along these faults that were interpreted as deep crustal faults from the magne c source modelling (Figures 03, 04 and 05). The Tentugal shear zone and its gold trend extend for more than 100 km along strike and are thought to con nue northward under the Cambrian-Phanerozoic cover. Fluid inclusion and isotope studies indicate that the gold was deposited by aqueous-carbonic fluids of low salinity. Temperature-pressure condi ons of these fluids of metamorphic origin were es mated between 260-380°C and up to 3 kbar (Klein, 2014). The similarity between the mineraliza ons of the Tentugal shear zone (N-NE Brazil) and Birrimian forma ons (W Africa) is par cularly evident from the presence of graphite-bearing material associated with both ore bodies.

Figure 04 - Colour composite (ternary) image of the Gurupi project area with interpreted structures.

48


A Prophile 47°0'0"W

46°30'0"W

46°0'0"W

B

Depth (Km)

2

4

Chega Tudo Fault 6

8

0

20000

30000

40000

50000

60000

70000

80000

88833

Distance (m)

E

W

Chega Tudo Fault Legend Chega Tudo Fm. Igarapé de Areia Fm.

C

Collisional granites

Figure 05 - (A) Area of the analytic signal map used for structural interpretation. (B) E-W profile of magnetic source depths (red dots) and inferred structures. (C) Regional geological interpretation and location of the Chega Tudo fault system.

References: KLEIN, E.L., 2014. Ore fluids of orogenic gold deposits of the Gurupi Belt, Brazil: A review of the physico-chemical properties, sources, and mechanisms of Au transport and deposition. In: GAROFALO, P.S., RIDLEY, J.R. (Eds.), Gold transporting hydrothermal fluids in the Earths crust, Geological Society, London, Special Publications, v. 402, p. 121-145..

49


Figure 06 - Predictive map of the Gurupi Belt orogenic gold system based on the integration of geophysical and geological data. Areas with a score higher than 3 are considered as the most prospective, as exemplified by the deposits of Cachoeira, Mina Nova Sul, Cachoeira, Chega Tudo and Cipoeiro.

50


Nova Brasilândia Project Elias M.G. Prado, Anderson A. Souza, Guilherme I.T. Guerra, Gustavo N. Bergami, Luciano C. da Silva, Thiago R. Rodrigues

The Nova Brasilândia Project is being developed by the Geological Survey of Brazil (CPRM) as part o f i t s p ro g ra m s “G e o l o g i c a l G e o p hy s i c a l Integra on and Predic ve Prospec vity Mapping of the Brasilian Shields” (Program I) and “Mineral Poten al Assessment of the Brazilian VolcanoSedimentary Sequences” (Program III). The studied area is located in Rondônia State and was selected a er the recent discovery of polymetallic sulfides in the metasedimentary sequence of Migran nópolis Forma on, Nova Brasilândia Group (Figure 01). The Nova Brasilândia Group (NBG) is divided into the Rio Branco and the Migran nópolis forma ons (Scandolara and Rizzo o, 1994). The Rio Branco Forma on comprises coarse and finegrained amphibolites, metagabbros and 550000

gabbronorites, in tectonic contact with h o r n b l e n d e - t re m o l i te - ga r n e t g n e i s s e s . I t exhibits a strong posi ve magne c anomaly, with rocks that were interpreted by Scandolara and Rizzo o (1994) as formed during ri ing and opening of a narrow proto-ocean. T h e M i g ra n n ó p o l i s Fo r m a o n o n t o p i s composed of siliciclas c sediments with a minor volcanic component, including kyanite-staurolite gneiss, sillimanite-muscovite-bio te gneiss, muscovite-bio te-feldspar-quartz gneiss with lenses of hornblende-tremolite-garnet gneiss, fine-grained amphibolite, metagabbroic sills and scarce metabasalts. The mineral assemblages of these rocks indicate metamorphism of upper amphibolite to granulite facies related to the closure of the basin. Low-angle tectonics

600000

650000

700000

Paresis Basins

8700000

Quartenary Basins

LEGEND Quaternary Basins Parecis Basins (Neoproterozoic/Paleozoic) Meso-Neoproterozoic Basin Meso-Neoproterozoic Mafic lntrusions Stenian Syn- to Late-tectonic Granites Carbonate Mine Zn,Pb,Cu 1 Au Ar sanal Mine Cu Ar sanal Mine

Nova Brasilândia Basin (Mesoproterozoic) Migran nópolis Fm. Quar zites Amphibolites Paragneisses Schist’s Calc-silicates Zn,Pb,Cu d: Au Occurrence Cu Occurrence

Figure 01 - Geological map of the Nova Brasilândia project area.

51

0

10

20km

Nova Brasilândia Basin (Mesoproterozoic) Rio Branco Fm Volcaninc and Plutonic Mafic Rocks with Cale-Silicate Lenses Ectasian Basement Calymmian Basement Thrust Fault Normal Fault Transpressional Shear Zone

8650000

Paresis Basins


affec ng the units masks the primary contacts between the metasediments and the mafic rocks. From the highly deformed rock sequences (Figure 02), a schema c stra graphic column prior to deforma on was recons tuted (Figure 03). The Migran nópolis sediments were deposited around 1215 ± 20 Ma either in an intracon nental ri or on a passive margin of the Amazonian Craton (Rizzo o et al., 1999) (Figure 04). Aeromagne c anomalies suggest that the NBG sedimentary sequence extends at least 500 km in the E-W direc on, with its eastern and western ends covered by Cretaceous and Quaternary sediments, respec vely (Figure 05).

Occurrences of Zn-Pb-Cu polymetallic sulfides were iden fied in areas prospected by Mineração Santa Elina. They are characterized by strongly oxidized massive and disseminated sulfide zones (surface gossans), iron oxide veinlets and stockworks, siliceous breccia and quartz veins. The Zn-Pb-Cu sulfide-rich hydrothermal breccia and gossans are hosted by muscovite-bio tefe l d s p a r- q u a r t z g n e i s s i n t e rc a l a t e d w i t h sillimanite-bio te-muscovite gneiss, hornblende-tremolite-garnet gneiss (calcs i l i c a t e ro c k s ) , fi n e - g ra i n e d a m p h i b o l i t e (metagabbro) and BIF. The massive sulfide zones occur as stra form mineralized lenses alterna ng

Quaternary Basin Arenites, sil tes and argillites Parecis Basin Conglomerates, Arenites, and argillites Meso-Neoproterozoic Basin Meta-psamites and meta-pelites

Quaternary Basin Arenites, sil tes and argillites

Migran nópolis Fm.

Quartzite

Parecis Basin Conglomerates, Arenites, sil tes and argillites

Schist Paragneiss

Meso-Neoproterozoic Basin Meta-psamites and meta-pelites

Amphibolite lenses Schist

Migran nópolis Fm. Quartzite

Calc-silicate lenses

Schist Paragneisses and meta-conglomerates with cacl-silicate and amphibolite lenses Zn, Pb, Cu Ore

Paragneiss Zn, Pb, Cu Ore Meta-conglomerate Thrust fault Rio Branco Fm. Paragneisses

Thrust fault

Mafic Volcanics Calc-silicate lenses

Rio Branco Fm. Paragneisses Mafic Volcanics with Calc-silicate lenses Mafic Plutonic

Mafic Plutonic Thrust fault

Thrust fault Mesoproterozoic Basement Ortogneiss Syn- to late-tectonic granite

Mesoproterozoic Basement Ortogneiss Mafic intrusion

Figure 02 - Stra graphic column of the deformed Nova Brasilândia volcano-sedimentary sequence.

Syn- to late-tectonic granite

Mafic intrusion

Figure 03 - Recons tuted stra graphic column of the Nova Brasilândia volcano-sedimentary sequence prior to deforma on.

52


Migran nópolis Fm.

Sandstones

Mafic volcanics

Crystalline basement Arkose, sandstones and siltstones

Mafic plutonics Conglomerates and turbidites

Shale and siltstones

Limestone and calcareous shale

Zn, Pb, Cu mineraliza on Rio Branco Fm.

Figure 04 - Paleoenvironmental reconstruc on of the Nova Brasilândia volcanosedimentary sequence, based on the model of SEDEX deposits from Emsbo (2009).

0

A Figure B

P i m e n t a

B u e n o

20

40km

G r a b e n

?

Rio Branco Fm.

C o l o r a d o

G r a b e n

-64°

-8°

-60°

BRAZIL

Au ar sanal mine

RONDÔNIA

Cu ar sanal mine

-12°

Cu occurrence

Nova Brasilândia Group

Zn-Pb-Cu occurrence

Project area

BOLIVIA

B

0

10

20km

Figure 05 - Aeromagne c map of the Nova Brasilândia project area. (A) Regional coverage showing the major magne c lineaments, Nova Brasilândia Group area, and metallic mineral occurrences. (B) Detailed coverage of the Nova Brasilândia Group area.

53


with sulfide-bearing muscovite-bio te-feldsparquartz gneiss. These polymetallic sulfide zones are 5-40 m thick and 0.3-3 km long.Hydrothermal altera ons with >25% of gahnite (Zn oxide) near siliceous breccias were con nuously mapped along a 2.5 km ESE-WNW trend. Most of the sulfide-rich zones occur concentrated along a magne c lineament of at least 50-km long, which was interpreted as a sinistral transpressional fault (Figure 06). The Zn-Pb-Cu sulfide deposit of Nova Brasilândia presents similari es with SEDEX-type deposits that have undergone high- grade metamorphism

such as for example in Broken Hill, Australia. The two deposits have comparable host rocks, geotectonic se ng, and metamorphic condi ons. Further studies by the Geological Survey of Brazil (CPRM) and associated universi es will be aimed at be er understanding the factors controlling this mineraliza on and at establishing a geological model. Syn and late tectonic A-type granites intruded NBG and affected the mineraliza on by increasing Sn and W grades in the gossans, in par cular near the contact with the plutonic bodies.

Figure 06 - (A) Gossan exposure including a massive sulfide vein (4 m thick) hosted by paragneiss of the Migran nópolis Forma on. Sample from this outcrop contains quartz, sulfides, gahnite and iron oxides, with composi on of 5.9% Zn, 0.74% Pb and 0.17% Cu; (B) Hand specimen showing weathered sulfides along the folia on plane and in veins, with composi on of 0.61% Zn, 1.1% Pb and 0.24% Cu.

References: EMSBO, P., 2009. Geological criteria for the assessment of sedimentar exhalative (sedex) Zn-Pb-Ag deposits: U.S. Gelogical Survey Open-File Report 2009-1209, 21 p. RIZZOTO, G.J., LIMA, E.F., CHEMALE JR., F., 1999. Acresção continental no Estoniano do sudeste de Rondônia. In: SBG-Núcleo Norte, Sim.Geol. da Amazônia, 6, Manaus-AM.

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Brazil Geological Survey under the Spotlight 2ª Edição

Geological survey of brazil under spotligth 2ª edição (distribuição)  
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