Upper and Great Western groups, Jackson Canyon, Old Baldy District, Santa Rita Mts, Pima Co., Arizona, USA

‡Ref.: Schrader, F.C. & J.M. Hill (1915), Mineral deposits of the Santa Rita and Patagonia Mountains, Arizona, USGS Bull. 582: 168, 173.

Arizona Bureau of Mines file data.

MRDS database Dep. ID file #10162339, MAS ID #0040190583.

A group of scattered Cu prospects with surface and underground workings located on claims located in sec. 31, T19S, R15E, from ¼ mile to ½ mile south of the Iron Mask Mine, in Jackson Canyon, and on the adjoining ridges, beginning at an elevation of about 6,000 feet and lying principally between 7,200 and 7,500 feet. Owned by Mr. McCleary.

Mineralization is fissure vein(s). The general country rock is rhyolite, which is intruded by masses of a dark-gray dense rock, probably a diorite, which is low in ferro-magnesian minerals and which, though seemingly related to the rock at the Jackson and Iron Mask Mines, is different. This diorite contains a large amount of disseminated magnetite and some pyrite, and nearly all the deposits are associated with it.

The rocks are traversed by east-west fractures, in the larger of which pyrite, chalcopyrite, and drusy, iron-stained quartz have been deposited. Films of the sulphides occur also on joint planes, of which one set trends northeasterly and another set northwesterly.

A second body of the diorite occurs on the ridge between Jackson and Birthday canyons at elevations between 6,360 and 6,600 feet. It trends north, is about 500 feet wide, and, like the larger body, contains widely disseminated pyrite and chalcopyrite and a few specks of native copper near the surface. The sulphides, which begin a few feet below surface, are mostly concentrated along north-south and northeast-southwest joint planes.