Abstract

The Tecoma deposit is in a mineralized low-angle, younger-over-older fault zone between the Devonian Guilmette Formation and the Mississippian Chainman Formation. Ore is predominantly in silicified carbonate and shale along the fault contact, with lesser amounts of dolomite and shale ore above and below the fault, respectively. The Tecoma deposit contains geologic reserves of approximately 1.5 million t of 0.05 OPT gold and 3 OPT silver. Ore contains barite, pyrite, hematite, acanthite, native gold, arsenic oxides, and mercury.

The deposit is in the eastern fringe of the Tecoma mining district. Historical production was from high-grade silver and lead replacement bodies along the axis of a northwest-trending anticline at the Jackson Mine. The district contains miogeoclinal rocks of Devonian through Permian age that are complexly faulted and folded, and intruded by altered quartz monzonite porphyry dikes and Tertiary rhyolite domes. Silicified bodies replacing carbonate and shale (jasperoid) are common throughout the district but are concentrated near the porphyry dikes.