A CONTRIBUTION TO ECONOMIC GEOLOGY GEOLOGY OF THE CHRISTMAS COPPER MINE GILA COUNTY, ARIZONA By NEJLS P. PETEKSON and EOGER W. SWANSON

The Christmas copper mine is in the Banner mining district, Gila County, Arizona. It is 8 miles north of Winkelman and 22 miles south of Globe. The mine was opened in 1905; to the end of 1943 it had produced about 55,340,000 pounds of copper. In 1946 it was operated under lease. The ore is high-lime fluxing ore, required by the smelter at Hayden. The ore produced during 1942 averaged 2.16 percent copper, but it contained no other metals paid for by the smelter. The mineral deposits are in a thick series of gently dipping Paleozoic limestones that range in age from Devonian to Permian(?). Overlying the limestones with only slight discordance is a thick sequence of Cretaceous (?) volcanic rocks, mainly andesitic tuffs, breccias, and flows. A small quartz diorite Stock has been intruded into the limestones and volcanic rocks. The Christmas fault cuts northwestward through the limestones, lavas, and the quartz diorite intrusive. The eastern part of the area has been depressed, bringing the lavas in contact with the limestones, which crop out west of the fault. The mineral deposits are of the contact metaniorphic or pyrometasomatic type. Chalcopyrite is the most abundant ore mineral, but variable amounts of bornite, chalcocite, and oxidized copper minerals are generally present. The gangue is chiefly garnet, quartz, magnetite, and unreplaced limestone. The factors that controlled the localization of the ore minerals are: (1) proximity to the limestone-quartz diorite contact, (2) favorable character of certain limestone beds, ( 3) -garnetization of the limestone, and (4) postgarnetization fracturing. The past production of the mine came mainly from ore bodies in the Naco limestone of Pennsylvania and Permian (?) age. A few small ore bodies have been mined from the Escabrosa limestone of Mississippian age. Other deposits of ore grade have been discovered by a drilling project carried on by the Bureau of Mines. Deep drilling below the .bottom level (770-foot level) of the mine alsa disclosed mineralized limestone in the lower part of the Martin limestone of Devonian age. The ore in the Naco occurs in flat tabular bodies which are replacements of certain favorable limestone beds close to their contact with the quartz diorite. The ore is confined to 11 distinct beds, which are consistently mineralized wherever they occur in favorable relationship to the contact. They constitute a zone about 425 feet thick of interbedded limestones and shale. The deposits in the Escabrosa are thick irregular bodies that lie against the contact.