RMAG ON THE ROCKS
Field Trip Report: Sediment Hosted Vanadium-Uranium of the Colorado Plateau October 29-30, 2021 Led by Dr. Ali Jaffri, Applied Stratigraphix, LLC Text and photos by Ronald L. Parker, Senior Geologist, Borehole Image Specialists, P.O. Box 221724, Denver CO 80222 ron@bhigeo.com
OUTCROP | January 2022
imaginable, yet the miners were attuned to the distinctive canary yellows of carnotite and tyuyamunite, the vibrant greens of torbernite and the brown blacks of roscoelite. Another miner’s observation was that U-V mineralization was best when alluvial architecture was assembled with a roughly 50:50 ratio of sandstone to mudstone - easily assessed by a quick visual sweep of the landscape. The geochemical rationale behind this idea is that oxidized waters carrying dissolved U and V oxyions follow the porosity and permeability in channel sandstones. The U and V oxyions are then immobilized by the reducing conditions – often mediated by included organic matter - prevalent in interstratified mudstones. We saw this 50:50 ratio of sand to mud repeatedly in regions with U and V mineralization. On Day 1, our itinerary was focused exclusively on the Salt Wash Member of the Upper Jurassic Morrison Formation in the Slick Rock district in San Miguel County, Colorado. For Day 2, we zeroed in on the Shinarump and Mossback Members of the Upper Triassic Chinle Formation in Grand and Emery Counties, Utah. To see our day 1 mines, we drove south on State 191 to Monticello, a righteous uranium town in its heyday. (Monticello was the site of the first ore-purchasing depot, established in 1948 by the US Atomic Energy Commission (AEC) (Amundson, 2004). Then, we headed east on State 491 toward the
When RMAG announced the field trip ‘Sediment-Hosted Vanadium-Uranium of the Colorado Plateau’, I was very pleased. As someone who has been interested in the hydrogeochemistry of Uranium (and the uranophile elements As, Mo, Se and V) since ~1986, this was a field trip opportunity that I had been waiting to attend for more than 25 years. And, it did not disappoint. Led by Dr. Ali Jaffri of Applied Stratigraphix, LLC., this excursion was a satisfying blend of sedimentology, stratigraphy, geochemistry, structural geology and, mining history with a rich variety of uranium and vanadium mineral occurrences. Almost everywhere we turned on this field trip, we saw vestiges of the glorious and forlorn boom-and bust cycles that have rippled through the social and cultural fabric of the Colorado Plateau over the past 120 years (Parker, 2015). Despite the end-of-October date, the weather was perfect for both days. The 5 attendees started the 1st day with a schedule, a safety refresher, a lecture on the history of U and V mining in the Colorado Plateau and an update on the most current ideas in fluvial sedimentology and U-V hydrogeochemistry. Dr. Jaffri also conveyed some of the wisdom of miners looking to emulate Vernon Pick and Charlie Steen who became household names in the 1950s as uranium millionaires (Coughlan, 1954; Ringholz, 2002). One common miners’ epithet was “follow the color.” Of course, the Colorado Plateau is splashed with a dazzling color palette of every color
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Vol. 71, No. 1 | www.rmag.org
