Redrock Mining District, Santa Cruz County, Arizona, USAi

Regional Level Types
Redrock Mining District	Mining District
Santa Cruz County	County
Arizona	State
USA	Country

A Cu-Ag-Pb-Zn-Au-Mn mining area located in T21-23S, R16-18E, G&SRM. This district adjoins the Wrightson District on the SE. It is 6 miles wide and extends from Sonoita creek between Patagonia and the Pennsylvania Ranch 11 miles southeastward to Meadow valley Flat and Canelo Pass. Harshaw Creek forms the southwest boundary, and the northeast boundary approximately coincides with the axis of the Canelo Hills. The first mining in the district was done by a party of Frenchmen who arrived in the late 1870's.

Three camps, the Hale, Jensen, and La Plata, were active circa 1915, and one additional was abandoned. Crittenden, on Sonoita Creek, where an adobe smelter was located in the early days, was at one time the principal town of the region, but Patagonia superseded it. The Hale camp was on Harshaw Creek, 4 miles SE of Patagonia, and the Jensen camp was in Redrock Canyon, 7½ miles in an airline SE of Patagonia.

Topography is mountainous and in part rugged.

The district contains four types of rock, which are disposed in parallel northwest-southeast belts. Beginning on the northeast they are limestone, conglomerate, andesite and rhyolite.

The limestone belt is only a part of a much broader belt of undifferentiated Paleozoic limestones that lie outside the district. Within the district the belt has a width of about a mile. It includes the crest of the Canelo Hills and their upper southwest slope. The general structure is that of a monocline dipping to the SW, with a fault plane somewhere along the northeastern flank of the hills. The belt is composed of relatively thick-bedded, cherty limestones of usually light gray color, which strike parallel to the ridge, about N35ºW, and dip 15º to 30º SW. These beds flatten to the east, near the crest of the range, on the eastern flank of which thin-bedded limestones dip to the SW at medium angles.

Overlying the limestone on the SW is a belt of coarse reddish conglomerate composed of pebbles and cobbles of red sandstone, limestone, chert, red rhyolite, and dark andesite cemented by sand, whose estimated thickness is between 300 and 500 feet. It dips 30º SW, and is probably of Tertiary age.

The valley of Redrock Canyon is underlain by flows of dark gray porphyritic andesite which overlie the sedimentary rocks of the Canelo Hills, usually overlapping the red conglomerate, and, toward the south, near Meadow Valley Flat, andesite also overlaps the older limestones.

A peculiar flat-topped hill a mile NNW of the Jensen Ranch is composed of reddish rhyolite similar to that of Red Mountain, south of Patagonia. The mountain which lies between Harshaw and Redrock canyons and reaches an altitude of 5,700 feet is also rhyolite, as is the spur running northeastward toward the flat-topped hill just mentioned.

The andesite flows of Redrock Canyon cover this rhyolite and have a rather even upper limit at elevations of about 4,900 to 5,100 feet. The andesite weathers into rounded forms of a dull-gray to chocolate-brown color. It is cut by an approximately east-west system of faults whose fissures are occupied by dikes of a black porphyritic, olivine-bearing basalt, also by dikes of a seemingly younger light colored acidic intrusive rock that trend in both east-west and north-south directions. Both of these intrusive rocks crop out boldly above the surface of the older mass.

The dome-shaped hill just northwest of Canelo Pass is composed of a rather coarse granite porphyry which is exposed on its west flank and is overlain by andesite. The andesite flow, however, is apparently thin, as it is reported that at depth of 70 feet in one mine the quartz porphyry was encountered under andesite, the contact between the two dipping about 30ºN.

Mineralization is: (1) Small, shallow, and generally weak, oxidized copper, lead, and zinc minerals, with some supergene enrichment in silver, associated with fault and fracture zones in Laramide andesitic and rhyolitic volcanics; and, (2) Manganese minerals in a fractured and brecciated zone in Jurasic welded tuff.

Workings are shallow shaft, adit, and open cut operations. Prospected and worked sporadically from the 1880's, mainly for pockets of high-grade silver.

Total production would amount to some 530 tons of ore containing about 20 tons of Cu, 21 tons of Pb, 2 tons of Zn, a few oz. of Au and 56,000 oz. of silver. A few tons of hand picked manganese ore were shipped.

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