Abstract

A hydrothermal mineral belt in south central Colorado is defined essentially by the intersection of early Eocene east-dipping, high-angle thrust faults with middle Eocene west- and southwest-dipping, low-angle thrusts, in a zone trending southeast from Kerber Creek to Huerfano Park. West-directed movement in the north, and east-directed movement in the south toward the old central Colorado basin, formed structural intersections of probable deep penetration. The intersections of late Eocene vertical uplift faults with Oligocene to Recent normal block faults along the edge of the Sierra Blanca massif formed a minor structural intersection and the subsidiary Sierra Blanca split of the mineral belt. Mineralized districts nearest the zone of intersection are Bonanza, Dennison City, Orient, Blake, Rito Alto, Silver Cliff, Rosita, Antelope Creek and Grayback. The Cleora, Badger Creek, Red Gulch, and Currant Creek districts, and numerous isolated prospects considerably northeast of the zone, tend to obscure mineral belt definition. However, the effects of severe deformation may extend laterally considerable distances from the zone center, and would broaden the belt. The belt width appears to extend farther northeast than southwest from the zone, probably because the northeastern faults are of steeper dips than those in the southwest and, consequently, of deeper penetration. Gravels of the San Luis and West Mountain Valleys probably conceal portions of the belt. Low productivity of the belt is attributed to weakness of mineralization resulting from parallelism of compressions, epithermal and disseminated character of the ores, and lack of systematic exploration.

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