Geochemistry of Tl and selected elements in four Carlin-Type Gold deposits
Four Carlin-type sediment hosted precious metals deposits and a rhyolite hosted precious metals deposit from the western United States have been analyzed for Ag, Au, Ba, Cu, I, K, Li, Mn, Pb, Rb, Sr, Tl, and Zn, and the relationship between Tl, Rb, and Kin mineralized and unmineralized rocks has been studied. Also evaluated is the enrichment of iodine over reported average elemental abundances in rocks using a revised spectrophotometric method. The Carlin-type gold deposits studied include Carlin, Jerritt Canyon, Alligator Ridge, and Mercur. The rhyolite hosted Rawhide deposit was studied as a comparison. The mineralized rocks of the Carlin-type deposits contain significantly higher concentrations of Tl than unmineralized samples. The Carlin and Mercur deposits have higher contents of Tl in the oxidized mineralized rocks than in the carbonaceous mineralized rocks. Using the Tl-Rb-K relationship, mineralized and unmineralized samples are separated into two distinct populations in the Carlin-type deposits and this analysis may be used to successfully outline potential mineralized areas. Iodine in the rhyolite hosted Rawhide gold deposit is found in concentrations more than .40 times those cited for an average rhyolite indicating that iodine may be an effective pathfinder element for volcanic hosted epithermal gold systems.
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