Palmetto Mine, Tres de Mayo Mine group, Fresno Canyon, Palmetto District, Patagonia Mts, Santa Cruz Co., Arizona, USA
|Latitude & Longitude (WGS84):||31° 26' 45'' North , 110° 48' 0'' West|
|Latitude & Longitude (decimal):||31.44583,-110.80000|
|Other regions containing this locality:||Sonoran Desert, North America|
‡Ref.: Schrader, F.C. & J.M. Hill (1915), Mineral deposits of the Santa Rita and Patagonia Mountains, Arizona, USGS Bull. 582: 290.
Schrader, F.C. (1917), The geologic distribution and genesis of the metals in the Santa Rita-Patagonia Mountains, Arizona, Economic Geology: 12: 237-269.
Galbraith, F.W. & D.J. Brennan (1959), Minerals of Arizona: 42.
Keith, Stanton B. (1975), Arizona Bureau of Mines Bull. 191, Index of Mining Properties in Santa Cruz County Arizona: 74 (Table 4).
Moger, S.R. (1970) Geology of the west central portion of the Patagonia Mountains, Santa Cruz County, Arizona: Davis, University of California, M.S. thesis, 60 p.
Anthony, J.W., et al (1995), Mineralogy of Arizona, 3rd. ed.: 144, 170.
Arizona Bureau of Mines file data.
A Cu-Ag-Au-Pb-Zn-Mn mine located in the SW ¼ sec. 3 & the N ½ sec. 10, T.23S., R.15E., a little south of the center of the district and a mile north of the Jarilla Mine, at an elevation of 4,452 feet. It was located in 1880 by A.J. Stockton and partners, of Patagonia. There were some old shafts already on the property indicating that it was worked earlier, perhaps by Mexicans. Owned at times, or in part, by Stockton; Backman & Merritt Mines Co.; Monarch Mining & Milling Co.; Taft Mining & Exploration Co.; Melville Syndicate; Newcomer; and, Cummings. Coordinates updated February, 2008, using a hand held Garmin GPS unit (shaft collar) by Ronald Deblois.
The country rock is quartz monzonite intruded by small, disconnected masses of diorite in the form of sheets and dikes. The quartz monzonite and the diorite near the contacts are both chloritized and epidotized, the diorite having apparently undergone the greatest alteration.
Mineralization is lenses of argentiferous galena with minor chalcopyrite and sphalerite in a quartz, psilomelane, and gouge gangue in 2 fissure-zone veins, oxidized to cerussite, acanthite, and rich chlorargyrite pockets. The wall rock is strongly sheared and fractured Precambrian rock intruded by Jurassic granite. A major fault passes through the area and a Northeast-striking fracture zone contains weak, oxidized sulfide mineralization. Psilomelane often contains lead and silver values.
The two veins are situated about 300 feet apart and are contained in the quartz monzonite in association with the intrusive diorite. The vein filling is white quartz, limonite, psilomelane, all much sheared and broken, forming a brecciated masss of yellowish-brown to black color.
The southwest vein dips 85ºSW. and is the vein upon which the shafts are sunk. It is 2 feet wide between walls of sheared quartz monzonite separated from the ledge matter by gouge. The principal ore mineral is argentiferous galena, but considerable ore rich in chlorargyrite was also produced.
Workings include 3 shafts and surface pits. Worked by Mexicans prior to 1880 but mainly from 1910 through 1942, producing in total some 200 tons of ore averaging about 70 oz. Ag/T, 25% Pb and minor Cu & Au.
7 valid minerals.
This geological map and associated information on rock units at or nearby to the coordinates given for this locality is based on relatively small scale geological maps provided by various national Geological Surveys. This does not necessarily represent the complete geology at this locality but it gives a background for the region in which it is found.
Click on geological units on the map for more information. Click here to view full-screen map on Macrostrat.org
1400 - 1600 Ma
|Middle Proterozoic granitic rocks|
Age: Calymmian (1400 - 1600 Ma)
Description: Mostly porphyritic biotite granite with large microcline phenocrysts, with local fine-grained border phases and aplite. Associated pegmatite and quartz veins are rare. This unit forms large plutons, including the Oracle Granite, Ruin Granite, granite in the Pinnacle Peak - Carefree area northeast of Phoenix, and several bodies west of Prescott. (1400-1450 Ma)
Comments: ~ 1.4 Ga
Reference: Horton, J.D., C.A. San Juan, and D.B. Stoeser. The State Geologic Map Compilation (SGMC) geodatabase of the conterminous United States. doi: 10.3133/ds1052. U.S. Geological Survey Data Series 1052.