Geology and ore deposits of the Steeple Rock mining district, Grant County, New Mexico

Abstract

The Steeple Rock mining district of western Grant County, N. Mex., is in an area of block-faulted Tertiary lavas that have been intruded by rhyolite dikes and plugs. About $7 million in metals, mainly gold and silver, has been produced from mines in this district since 1882. A body of base-metal sulflde ore, uncommon in the Steeple Rock district, was exploited at the Carlisle mine from 1943 to 1946.The ore occurs in veins that occupy premineralization faults which cut the volcanic sequence. The faults belong to three groups, but nearly all the known ore is closely related to the northwest-trending group or to fault intersections.The sulfide ore occurs in a breccia zone at the intersection of the east-trending Carlisle fault and the northwest-trending Apache fault. The sulfide ore minerals are sphalerite, galena, and chalcopyrite in a gangue of quartz and altered breccia. The precious-metal ores of the district, which are associated with quartz in fault breccia, were not being mined at the time of the investigation and could not be studied in detail. In one rich specimen the silver-bearing mineral is argentite; gold probably occurs as the native metal. Additional bodies of goldsilver ore probably will be discovered.