Seminoe Mountains greenstone belt

The Seminoe Mountains greenstone belt represents a fragment of an Archean greenstone terrane within the Wyoming craton. The greenstone belt was mapped by Hausel,[1] who identified significant gold anomalies at Bradley Peak in banded iron formation, quartz veins and in a large altered zone of metabasalts. Mapping differentiated three mappable units that included the Bradley Peak metavolcanics, the Seminoe Formation and the Sunday Morning metasediments.

Mineral resources in the belt are varied, as is typical of most greenstone terranes. The mineral resources have not been explored in any great detail and indications are some deposits could be economic under favorable conditions. Low-grade iron deposits are widespread and include a minimum resource of 100,000,000 tons. Lapidary and decorative stone is varied and includes several types of attractive rock including serpentinite, leopard rock, jade, jasperized banded iron formation, and copper-coated (malachite, chrysocolla, cuprite) milky quartz. Copper mineralization is localized and does not represent a significant resource, as may be the same for zinc and lead.

In past years, exploration efforts have been geared to the testing of narrow quartz veins and the possibility of broader auriferous pods enclosed in altered rock has been neglected. The altered zone in the vicinity of the Penn mines should have been considered as a target for widespread low-grade gold mineralization with potential credits in silver, copper, lead, and zinc.