12th GEOSEA 2012, Bangkok, Thailand
Geology and Petrochemistry of dike rocks in Chatree gold mine, Pichit province: Implication for Late Paleozoic tectonic setting
Tangwattananukul L1, Takasima I1, Misuta T2 Ishiyama D2 and Lunwongsa W3, Charusiri P4
Graduate School of Engineering and Resource Science, Center for Geo-Environmental Science, Akita University, 1-1 Gakuen-Machi, Akita 010-8502, Japan 2 International Center for Research and Education on Mineral and Energy Resources, Akita University, 1-1 Gakuen-Machi, Akita 010-8502, Japan 3 Exploration section, Issara Mining Company, Phechabun, Thailand 4 Earthquake and Tectonic Geology Research Unit (EATGRU), c/o Department of Geology, Chulalongkorn University, Bangkok 10330, Thailand 1
ABSTRACT The inferred Permo-Triassic Loei-Phetchabun volcanic rocks of mainly intermediate to mafic large and volcaniclastic were cut by dike rocks of intermediate composite in the Chatree gold mine. Almost all the least-altered dike rocks can be divided into two types, based on their field occurrence, i.e. the NE-SW and N-S trending dikes. The latter are cross cut by the former. Most dikes are cut ore vein/ veinlets but dike postdate then. The north-south trending dikes chemically compositions have more mafic than northeast-southwest trending dike rocks. Most northeast-southwest dike rocks have porphyritic texture with phenocrysts and microphenocrysts of mainly plagioclase with minority of clinopyroxene, olivine and Fe-oxide opaque. The groundmass generally range from felty to trachytic, the northsouth trending dikes usually show ophitic to subophitic and glassy textures, however a few samples are holocrystalline. The N-S trending dike rocks seem to contain more mafic minerals than the NE-SW trending rocks. However both dike rocks are much for hydrothermally altered than the volcanic host rocks. Geochemically, the dike rocks contain silica content ranging from 40.2 – 56.6%. Immobile elements geochemistry of dike rocks indicates the composition between andesite or basalt and subalkali basalt. Trace element data show north-south dikes are tholeiitic in composition than the northeast-southwest dike. The geochemical characteristics of the high-magnesium are typical of subduction-related magmas, with negative Sr and Zr spikes in mantlenormalized diagrams. Chondrite-normalized rare earth elements (REE) pattern indicated that the both dike rocks are somewhat enriched in light rare earth elements (LREE), with flat heavy rare earth element (HREE) pattern. Then, chondritenormalized patterns of dike rocks compared to that of the Andean continental show a parallel pattern, suggesting that both dike rocks may have formed by subduction of Nakhon Thai-oceanic plate beneath than Indochina continental plate with the contratins melts. Keywords: Dike, Chatree, trace element, REE, subduction, Late Paleozoic 79 79 GEOSEA 2012