|Latitude & Longitude (WGS84):||31° 25' 41'' North , 110° 42' 11'' West|
|Latitude & Longitude (decimal):||31.42833,-110.70306|
|Other regions containing this locality:||Sonoran Desert, North America|
|Köppen climate type:||BSk : Cold semi-arid (steppe) climate|
A former small underground Pb-Ag-Zn-Cu-Au-Mn (Be-Mo-V-Sb) mine located on 21 patented claims totalling 420 acres in the NW¼ (S½SW¼ ?) sec. 15, T.23S., R.16E. (protracted), 1.5 miles SE of American Peak, in the south base of Mowry Hill on the north side of Mowry Wash, 4 miles North of Duquesne (Washington Camp), 5 miles South of the Trench Mine, 9 miles south of Patagonia, and about 75 miles South of Tucson, at about 5,500 feet of altitude, on private land. Started before the civil war, worked in the 1850's by Mexicans. Relocated and reopened about 1857-58 by Lt. Sylvester Mowry. Produced 1864-1952. Owned at times, or in part, by Col. Titus & Brevoort (1859); Lt Sylvester Mowry bought it in 1860 for $25,000; Fish, Bennet & Co. (from June, 1875); Fish & Silverberg; Steinfeld & Swain; Mowry Mines Co.; Santa Cruz Mining & Smelting Co.; Mitchell; Stone; B. Logan; K. Peterson; T.L. Woodruff; G.M. Grant & Woodruff; F. Metler (Metter); the U.S. Mining And Smelting Co. (1967); J.W. Douglas; R.S. Ewell; J.N. Moore; Randall; Lord; Doss; H.T. Titus; Silverberg and Steinfeld (1890-1901); General Carleton (1862-1864); Mowry Mines Co. (1904-1907); A.J. Hazeltine; Fish; Stone; J. Curtis; White and Lovelace; M. Encinas; H. Miller; F.J. Gallagher; Squires; W.J. Mitchell; Standard Metals Co.; Mowry Exploration Co.; Southwest Metallurgical Industries (1955).
Mineralization is argentiferous galena and secondary minerals in tabular replacement orebodies, with ferruginous and manganiferous gangue, along a strong fault zone and associated fissures in Paleozoic limestone. The ore zone is 864.65 meters long, 6.1 meters wide, with a depth to bottom of 152.4 meters, striking N75E, dipping 80N. Deep oxidation and supergene enrichment produced high-grade lead-silver ore in the upper section. Pods and pockets of psilomelane and pyrolusite occur in fracture zones in the limestone. The ore contains little, if any, quartz and no zinc.
The mine is on an east-west fault contact between the Paleozoic limestone and the Mesozoic quartz monzonite. The fault, called the Mowry fault by Schrader & Hill, trends N.75ºE. and dips 78ºN. and seemingly is normal. The limestone occurs on the north or hanging wall side of the fault and the quartz monzonite on the south side. The limestone essentially composes the adjoining Mowry Hill, which rises about 300 feet above the mine and seems to represent the northern part of a low dome or anticline whose southern part has been cut off by the fault, for in the east slope of the hill, the rock dips 45ºNE. At the top of the hill they dip to the north and in the west slope they dip to the northwest at about the same, or slightly less angles. Along the fault they dip 45º to 70ºN., away from the contact.
At some time later than the faulting the rocks and the fault were disturbed along a fault or shear zone about 200 feet in width, which strikes N.30ºW., and stands about vertical and which, as shown on the Mowry fault at the mine, has offset the formations by a small horizontal displacement, the rock on the east being moved 45 feet to the south. To the east of this later fault, which will be referred to as the north-south fault, the limestone for a short distance strikes N.45ºW. and dips 50ºNE; west of it the strike is N.45ºE. and the dip more regularly to the northwest at about 28º. To the north up the slope the zone dies out just below the top of Mowry Hill, apparently pasing into undisturbed cherty limestones that strike N.85ºW. and dip 43ºN. On the south, where the fault zone is about 250 feet wide, it is composed of a red iron-stained silicified breccia, apparently composed mainly of chert pebbles, which at the top of the hill seems to run into a bed of dark gray cherty limestone that continues northwestward down the west slope of the hill.
Away from the locally disturbed beds along the north-south fault the limestones are unaltered, dark blue-gray in color, thin to heavy bedded, and in places cherty. They aggregate at least 800 feet in thickness.
The limestone is much purer along the north-south fault than away from it, but along the Mowry fault some of the limestone has been metamorphosed to a fine-grained marble. The limestone contains also some interbedded quartzite.
The quartz monzonite south of the Mowry fault is a reddish-gray, massive, porphyritic granitoid rock with phenocrysts of feldspar and inch in diameter. It is composed mainly of orthoclase, oligoclase-andesine, and quartz in about equal amounts, the orthoclase including some microperthite and microcline. Considerable dark silicate is present, some as biotite but most as hornblende, which, however, is nearly all altered to heavy, dark green masses consisting principally of chlorite or allied decomposition products and oxide of iron. Apatite is present as an accessory mineral, and some pyrite, marcasite, and chalcopyrite occur as secondary minerals. The rock on the whole is considerably altered, especially the soda-lime feldspars, which are highly sericitized. It is classified with the Mesozoic intrusive rocks, and is regarded as intrusive into the limestone. For 60 to 100 feet back from the Mowry fault the rock is much altered and stained with iron and manganese, and along the fault it is sheared and crushed, and the nearly parallel shear planes dip steeply to the south, away from the fault.
Croppings extend interruptedly along the contact fissure for more than 1/2 mile. The deposit forms an almost continuous tabular sheet along a 600 foot stretch occupied by mine openings. Ore shoots occur at intervals along a NE-trending vein and pitch 40-60SW. Several deposits occur as mantos, following limestone for several 100's of feet beyond the shear zone.
The Mowry fault is offset by west end and east end faults; The west end fault block is laterally displaced 50 feet to the south. Copper and iron sulfides were first encountered on the 400 foot level. Coarsely crystalline galena occurs in lenses and masses embedded in manganiferous gangue. A large ore body and several sheets or veins of Mn are found at the 150 foot level. The lack of quartz and zinc is noteworthy. The quartz monzonite is underlain by a gabbro intrusion at the 235 foot level.
Cropping out at several points in the camp southwest of the mine and seemingly intruding the limestone along the Mowry fault in the deep part of the mine, is a dark greenish or nearly black, massive, medium-grained, crystalline rock locally known as basalt, and in the mine, where it approximately parallels the fault and vein, it is known as the '500-foot lime dike.' It is actually an almost typical gabbro, composed mainly of labradorite or closely allied basic soda-lime feldspar, augite, or other pyroxene and contains considerable magnetite and iron, some biotite, and seemingly olivine, with accessory apatite. The rock on the whole is highly altered. The augite, whose abundance in places is indicated by the form of the crystal casts, is mostly changed to green amphibole, smaragdite, and chlorite, and the feldspars are greatly kaolinized and altered to epidote. Calcite and magnetite are present as secondary minerals, the former occurring both in isolated crystals or grains and in macroscopic veinlets and seams on joint planes and fracture lines, together with a few seams or veinlets of secondary quartz.
The manganese deposit is on the north or hanging wall side of an East-West fault contact between Paleozoic limestone and quartz monzonite. Gabbro intrudes the limestone along the fault. From surface the vein extends downward (500 feet) to the bottom of the mine in a continuous sheet and was ore-bearing almost throughout. Most of the orebodies; however, occur apparently as replacements of the adjacent limestone. The Mn + Fe formation is about 20% of the total orebody.
Tectonic elements include the Mowry Falt Block with downthrow to the north.
Workings include an 'old' shaft at 350 feet deep (1881), additional shafts and numerous tunnels and drifts. There are 15,000 feet of drifts, raises, and winzes connecting to the surface by at least 6 shafts. Developments included diamond drilling (1954-1955) by Ventures Ltd. of Cananda. This mine was probably worked by Jesuits and Mexicans prior to 1850 and later was mined up through 1952. Total estimated and reported production of Pb-Ag ore would be some 200,000 tons averaging about 4% Pb, 3 oz. Ag/T, and minor Cu, Zn, and Au. During WWI & WWII, some 7,500 long tons of about 25% Mn were shipped.
24 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
66 - 145 Ma
|Mesozoic sedimentary rocks|
Age: Cretaceous (66 - 145 Ma)
Lithology: Sedimentary rocks
Reference: Chorlton, L.B. Generalized geology of the world: bedrock domains and major faults in GIS format: a small-scale world geology map with an extended geological attribute database. doi: 10.4095/223767. Geological Survey of Canada, Open File 5529. 
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.