Geology and geochemistry of the colt mesa copper deposit, Circle Cliffs Area, Utah

The Colt Mesa copper deposit, Circle Cliffs area, Utah, is located at the contact of a paleochannel deposit of the Shinarump Member of the Chinle Formation and the underlying Moenkopi Formation. The ore body is tabular in form and is composed of chalcopyrite, bornite, digenite covellite, and chalcocite. Minor amounts of zinc, lead, cobalt, nickel, molybdenum, uranium, vanadium and silver are associated with copper mineralization. The Colt Mesa deposit is genetically similar to uranium deposits in the Circle Cliffs area. The ore fluid was a low temperature, dilute aqueous medium such as groundwater. All of the elements enriched in the ore zone are soluble at low concentrations in an oxidizing, neutral to slightly acid environment. Precipitation of ore elements as sulfides was caused by a decrease in the Eh of the ore solution. The greater range of solu­bility of uranium indicates that it can remain in solution after the precipitation of copper.