Igneous rocks and copper mineralization in the Ray porphyry copper district, Arizona

The Ray porphyry copper district is approximately 110 km north of Tucson and 120 km east-southeast of Phoenix in southeastern Arizona. The major disseminated copper deposit at Ray has reserves estimated at 650 million tonsl of both primary and secondary ore, and occurs mostly in Precambrian Pinal Schist and diabase, but partly in the Granite Mountain Porphyry of Laramide age. The Granite Mountain Porphyry is part of a suite of Laramide igneous plutons and dikes in the Ray area that range in age from 70 to 60 m.y. and in composition from diorite to quartz monzonite. Hydrothermal biotite from the copper deposit at Ray has been dated at 65 m.y. (K-Ar age), and apatite in mineralized diabase has been reset at 60 m.y. (fission-track age). These ages indicate a close temporal and possibly genetic relationship with these Laramide igneous rocks.