Paleokarst Controls on Localization of Uranium at Pitch Mine, Sawatch Range, Colorado: ABSTRACT

Abstract

The Pitch Mine is located at the southwestern end of the Sawatch Range in south-central Colorado. Currently being developed by Homestake Mining Co., the deposit has 7 million lb (31.5 million kg) of U3O8 delineated reserves. The uranium mineralization largely occurs in the black organic-rich matrix material of carbonate These breccias have previously been described as Pennsylvanian Belden Formation fault breccias. They are, however, morphologically similar to the Upper Mississippian fossil karst breccias within and on top of the Mississippian Leadville Formation, which host silver and base-metal mineralization in several areas of the Sawatch Range. Paleokarst relief is well exposed on the Leadville Formation within a few miles of the Pitch Mine. The karst features include lines of what appear to be karst towers with their associated sinkholes and rare preserved red-soil The towers are morphologically similar to other Late Mississippian karst towers in the Molas Lake area of southwestern Colorado. The carbonate breccias formed by surface karst weathering, as washed-in cave and sinkhole fill, and by sinkhole collapse. The black clayey matrix material was deposited in the lakes and swamps of a drowned karst regime such as the Everglades and sinkhole lake country of the Florida Peninsula today. Both the mineral assemblage and alteration at the Pitch are limited, indicating a low-temperature origin for the uranium. End_of_Article - Last_Page 826------------