Geology and ore deposits of the Dragoon quadrangle, Cochise County, Arizona

Abstract

The area described in this report is in Cochise County in southeastern Arizona and comprises a little more than 250 square miles in the northwestern part of the county. The mining district known as Johnson Camp is near the center of the area, and the village of Dragoon on the Southern Pacific Railroad is near the southeastern corner. The area is in the Mexican Highland section of the Basin and Range province and straddles the divide between the San Pedro valley on the west and the Sulphur Spring valley on the east. The Little Dragoon Mountains in the south-central part of the area constitute the principal topographic feature. In the eastern part are the north tip of the Dragoon Mountains, the Gunnison Hills, the Steele Hills, and the south tip of the Winchester Mountains. In the west-central part are the Johnny Lyon Hills, from which a ridge extends northward and joins the Galiuro Mountains north of the area described. The rock formations of the area range in age from Precambrian to Recent. The oldest rocks are moderately metamorphosed graywackcs, slates, and lava flows that make up the Pinal schist of early Precambrian age. Also early Precambrian are rhyolite porphyry intrusive sheets and stocks, a large granodiorite mass in the Johnny Lyon Hills, and granite exposed at the south end of the Winchester Mountains. The Tungsten King granite and associated aplite on the west side of the Little Dragoon Mountains, and granite exposed at the north end of the Dragoon Mountains are also referred to the early Precambrian but could be younger. Upper Precambrian rocks, generally unmetamorphosed, include the Scanlan conglomerate, Pioneer shale, Barnes conglomerate, and Dripping Spring quartzite which are part of the Apache group; extensive diabase sills of Precambrian age were intruded into these rocks.