Abstract

The Tallman gold deposit is a small, low-grade, open-pitable, “Carlin type” disseminated orebody hosted in carbonaceous siltstones of Middle Pennsylvanian age. The proven ore reserve, in one large and three small deposits, totals 530,000 t at a grade of just over 0.07 oz of gold/t. A large area surrounding the ore bodies is geochemically anomalous in gold and this suggests that much more ore may be found with continued exploration of the district.

The rocks exposed in the district are dominantly limestone, dolomite, and quartzitic sandstones that have been extensively deformed by folding, thrust faulting, and high-angle faulting. Siltstones are locally abundant in three mapped formations and are believed to be particularly favorable host rocks for the gold mineralization. Intrusive rocks are present only as narrow dikes of altered material that probably was originally of intermediate composition. The dikes crop out in only a few places but float has been seen at many localities.

Quartz veins that locally contain small concentrations of high-silver tetrahedrite occur at several localities within a widespread breccia unit. These veins, which have not been found to contain significant ore bodies as yet, are thought to have formed during an earlier period of mineralization than that which produced the disseminated gold deposits.