Precambrian sulfide deposits in the Gunnison region, Colorado
— Douglas M. Sheridan, William H. Raymond, and Leslie J. Cox

Base-metal massive sulfide deposits are currently of considerable economic interest because they are characteristically high in grade. Such deposits are mined mainly for copper, zinc, and lead, but some also contain recoverable silver and gold. New exploration has been stimulated in many parts of the world by numerous studies during the last two decades concerning various syngenetic and exhalative processes of origin and the relation of stratabound sulfide deposits to certain types of host-rock lithology (King and Thompson, 1953; Horikoshi, 1969; Anderson, 1969; Matsukuma and Horikoshi, 1970; Sangster, 1972; Stanton, 1972; Hutchinson, 1973). Many massive sulfide deposits in various places in the world are now considered to be volcanogenic. Using the newer geologic concepts and newer, more refined guides to ore, mining companies have made some outstanding new discoveries, including, for example, the recent finding of two large Precambrian deposits: one containing more than 7 million tons* of zinc-copper-lead ore at Izok Lake in the Northwest Territories, Canada (Money and Heslop, 1976, p. 24-25), and another having 60 million tons of zinc-copper ore at Crandon, Wisconsin (Eyde, 1977, p. 51).

The search for minable Precambrian sulfide deposits has been extremely active in recent years in numerous areas in Colorado, New Mexico, and southern Wyoming. The initial stimulus for this renewal of interest likely was given by Giles' suggestion (1974) that a significant part of the Precambrian terrain in northern New Mexico and southern Colorado may be a "previously unrecognized volcanogenic massive sulfide metallogenic province." Data presented by Sheridan and Raymond (1977) indicated that representative samples from many long-ignored Precambrian sulfide deposits distributed throughout western Colorado are of a grade suggesting potential economic significance.

The present report is a brief description of the geology of Precambrian sulfide deposits in the Gunnison region, Colorado. In other reports in this guidebook, the Precambrian geology along parts of the Gunnison uplift is described by D. C. Hedlund and J. C. Olson, syngenetic sulfide mineralization in the Gunnison Gold Belt is described by P. A. Drobeck, and the stratigraphy, petrology, and structure of Precambrian metamorphic rocks in the Iris district are described by A. M. Afifi.