Altered wallrocks in the central part of the Front Range mineral belt, Gilpin and Clear Creek Counties, Colorado

Geology and ore deposits of the Lawson-Dumont-Fall River district, Clear Creek County, Colorado

“…The alteration of the wallrock in this and nearby districts has been discussed in detail by Tooker ( 1963). The discussion here is based primarily on his work :and on the megascopic character of the alteration, but also in part on a detailed study of rock alteration along some pitchblende-bearing veins in Fall River.…”

“…Reports on parts of the dis- The Lawson-Dumont-Fall River district was studied from 1952 to 1954 as a part of a comprehensive investigation of the mining districts in the central part of the Front Range mineral belt by the U.S. Geological Survey on behal:f of the U.S. Atomic Energy Commission. These studies, under the supervision of P. K. Sims, consisted primarily of geologic mapping and economic studies of the ore deposits in the districts, but in addition included intensive investigations of the Tertiary igneous rock sequence (Wells, 1960) and of wallrock alteration (Tooker, 1963}. Major reports that have resulted from the mapping in the mining districts include those by Harrison and Wells on the Freeland-Lamartine district (1956) and the Chicago Creek area (1959}; reports by Sims, Armstrong, and others (1963) and Sims and Sheridan (1964) on the uranium deposits of the Front Range mineral belt; a report by Sims, Drake, and Tooker (1963} on the Central City district; and a report by Moench and Drake (1966) on the Idaho Springs district.…”

“…Clay minerals found in the altered rocks are kaolinite, illite, montmornlonite, and mixed-layer clays, Tooker, 1963).…”

Economic geology of the Idaho Springs district, Clear Creek and Gilpin Counties, Colorado

“…The Lawson-DumontFall River area to the west was studied by C. C. Hawley and F. B. Moore, and the Central City district to the north was studied by Sims, Drake, and Tooker (1963). Specialized studies of the uranium deposits (Sims, Drake, and Tooker, 1963;Sims and others, 1963;Sims and Sheridan, 1964), Tertiary igneous rocks (Wells, 1960), and wallrock alteration (Tooker, 1963) were also made.…”

“…This belt extends aINTRODUCTION uranium deposits of the region, including the few small deposits in the Idaho Springs district. Tooker (1956; studied the altered wallrocks adjacent to the veins in the region. The results of these specialized investigations within the district by Tooker, Wells, and Sims and others are summarized in this report.…”