Bagdad, Eureka District, Yavapai Co., Arizona, USA

‡Ref.: Anderson, C.A. (1950), Alteration and metallization in the Bagdad porphyry copper deposit, Arizona, Economic Geology: 45: 609-628.

Wilson, E.D., et al (1950), Arizona zinc and lead deposits, part I, Arizona Bureau of Mines Bull. 156: 122-125.

Galbraith, F.W. & D.J. Brennan (1959), Minerals of Arizona: 72, 98, 99, 111.

Medhi, P.K. (1978) Recent geological developments at the Bagdad porphyry copper deposits, Eureka mining district, Yavapai County, Arizona [abs.], in Jenney, J.P., and Hauck, H.R., eds., Proceedings of the Porphyry Copper Symposium, Tucson, Arizona, March 18-20, 1976: Arizona Geological Society Digest, v. 11, p. 79.

Anthony, J.W., et al (1995), Mineralogy of Arizona, 3rd.ed.: 161, 240, 262, 359.

Bagdad is located in west-central Arizona, 42 miles west of Prescott. The Bagdad area is a part of the much larger Eureka District.

The Bagdad area is recognized primarily as a copper district but notable amounts of Pb Zn have been mined in the area.

About two thirds of the rocks exposed in the Bagdad area are of Precambrian age. The oldest, the Yavapai schist, consists of amphibolite and mica schist derived from original lava flows, tuff, tuffaceous sediment, sandstone and shale. Sufficient relic textures and structures are preserved to detect the original characters. These rocks were folded, faulted, and intruded by a series of Precambrian igneous rocks culminating in widespread granite. The oldest of the intrusive rocks is a metarhyolite to which the Old Dick and Copper King mines are spatially related.

In the western part of the Bagdad area, rhyolite tuff rests on an eroded surface of alaskite porphyry. This tuff is probably late Cretaceous or early Tertiary in age. The quartz monzonite crops out in a series of stocks and plugs; the largest stock contains the copper ore mined at the Bagdad mine. Diorite porphyry and quartz monzonite porphyry dikes cut the quartz monzonite but probably belong to the same period of igneous intrusion.

During the Pliocene or Pleistocene, a surface of considerable relief was partly buried by Gila (?)conglomerate and intercalated basalt flows.

The Mountain Spring fault cuts the Precambrian rocks but is older than the quartz monzonite. The dip-slip displacements on this west-dipping normal fault is probably between 1,000 and 3,000 feet. The Hillside fault, also a west-dipping normal fault, but of unknown total displacement, cuts the Yavapai schist and younger rocks. This fault forms the fissure vein at the Hillside mine. Post-ore movement has displaced the Gila (?) conglomerate and lava flows 250 to 300 feet. The Mountain Spring and Hillside faults may have been connected prior to quartz monzonite intrusion.

The Hillside and Mountain Spring faults probably exerted a broad control over the distribution of the Au-Ag-Pb-Z-Cu deposits in the area. Deposits of these metals are limited essentially to a north-trending zone 2 miles wide; the faults are in the middle of this belt.

The Bozart and Hawkeye faults are of post-Gila (?) age and show displacements of 100 to 30 feet. These two faults are probably conected under an appreciable blanket of talus and soil.

In 1887 lead, associated with gold-silver ore was mined, and, by the end of 1945, 6,625,835 pounds of recoverable lead, valued in excess of $350,000 (period values), had been reported. Zinc mining started in 1917, and, by the end of 1945, 12,376,697 pounds of recoverable zinc having a value of $938,465 (period values) had been reported.