Rocks locally consist of Precambrian crystalline rocks, chiefly of granitic composition, cut by large masses of mesozoic (?) granite. Dikes are scattered throughout the area. Some are parallel to the prominent northwest-trending system of veins, but others trend in various directions. Remnants of volcanic rocks of probable Tertiary and Quaternary age are around the margins of the Cerbat rangebut are not present in the district proper.
The Precambrian rocks consist of a complex of amphibolite, hornblende schist, biotite schist, chlorite schist, diorite gneiss, granite and associated pegmatitic bodies, granite gneiss, schistose granite, granitic schist, and garnetiferous schist. Granite and amphibolite are the most widespread types, and the granite is predominant.
The amphibolite which is one of the oldest rocks in the area, is a dark green to black, fine to medium-grained rock commonly epidotized and cut by granite pegmatite intrusions. It is widey distributed throughout the area but is particularly conspicuous near Chloride and in the low hills between Cerbat Canyon and Mineral Park Wash.
The Precabrian granites are representedy many types. Some of the bodies are distinct and separate intrusions but others are probably differentiation facies. Typically the rock is light grey, medium-grained, gneissoid granite containing a small amount of mafic minerals, chiefly biotite. Weathered surfaces are usually light buff, less commonly reddish-brown.
Near Mineral Park in the central part of the district a large granite stock has intruded the Precambrian granites, gneisses, and schists. Its age is tentatively assigned to late Jurassic or early Cretaceus, the same as the batholiths of California and western Nevada. The granite is essentially medium-grained, slightly porphyritic, and intensely altered, although there are many facies of fine- or coarse-grained granite, granite porphyry, porphyritic granite, and granite pegmatite. Numerous small stocks and irregular bodies of greenish-black gabbro and associated diabase dikes occur most commonly in the southern part of the district. These are probably differentiation facies of the granite stock. Mineralizing solutions that formed the veins in the district are believed to be genetically related to the late Mesozoic (?) granite intrusion.
Dikes of many different compositions are widespread. In tickness they range from a few inches to 300 feet. Some extend along strike for only a hundred feet or less whereas others, notably the rhyolites, extend for long distances. The most abundant dike rocks are granite pegmatites of both Precambrian and late Mesozoic (?) age, and dikes formed from them are usually narrow and of short lateral extent. Aplites are not common. Other dike rocks, some of which are abundant locally, include lamprophyre, andesite, diabase, porphyritic granite, granite porphyry, and rhyolite, and are probably differentiation products of the late Mesozoic (?) intrusion.
The structure of the rocks is complex. Gneissic and schistose structures are common; the prevailing schistosity strikes NE with steep dips either NW or SE. Large and small folds, generally with NE trends, are common. The most predominent fold is near Chloride where the outcrop pattern of te amphibolite indicates a northeast-plunging anticline. Prominent joint systems, sheeting, and small shear zones, commonly with NW srikes, are abundant. Faulting is widespread and is usually well-expressed by a prominent system of northwest-trending fault fissures in which many of the later veins are located. The dips of the fissures are generally steep, and NE dips predominate. In places the fault fissures are in conjugate systems. The fissures show much branching and in a few places considerable horsetailing. Gouge and breccia, as well as numerous tear faults in the walls, are present along some fault fissures. The direction of the striations along the walls of the faults is nearly horizontal in places, but a greater number of striations show dips ranging from horizontal to parallel with the dip of the steep fault surface.
Deposits are mesothermal veins of prevailing northwestward strike and steep dip. Their gangue is quartz, in many places shattered and recemented by later calcite. The primary minerals are common sulfides of iron, lead, zinc and silver. Gold occurs locally in the sulfide zones. Oxidized zones contain secondary lead minerals, native silver, gold and silver chloride.
Total value of Au-Ag-Cu-Pb-Zn produced in the district from 1901 to 1946 was $23,984,960 (period values). Several additional millions may be attributed to production prior to 1901 for which records are poor.
Mineral ListMineral list contains entries from the region specified including sub-localities
137 entries listed. 85 valid minerals.
Localities in this Region
The above list contains all mineral locality references listed on mindat.org. This does not claim to be a complete list. If you know of more minerals from this site, please register so you can add to our database. This locality information is for reference purposes only. You should never attempt to visit any sites listed in mindat.org without first ensuring that you have the permission of the land and/or mineral rights holders for access and that you are aware of all safety precautions necessary.
The Resources of Arizona - A Manual of Reliable Information Concerning the Territory, compiled by Patrick Hamilton (1881), Prescott, AZ: 66-67; Wilson, E.D., et al (1934), Arizona Bureau of Mines Bull. 137: 109-110; Anthony, J.W., et al (1995), Mineralogy of Arizona, 3rd.ed.: 126, 128, 161, 169, 185, 190, 196, 205, 233, 235, 259, 261, 286, 290, 297, 309, 332, 341, 359, 365, 370, 377, 396, 432; Haury, P.S. (1947), Examination of lead-zinc mines in the Wallapai mining district, Mohave Co., AZ, US Bur. of Mines Rept. Inv. 4101; Thomas, B.E. (1949), Ore deposits of the Wallapai district, AZ, Econ.Geol.: 44:663-705; Field, W. (1966), Sulfur isotope method for discriminating between sulfates of hypogene and supergene origin, Econ.Geol.: 61:1428-1435; Galbraith, F.W. & Brennan (1959), Minerals of AZ: 25, 60, 64, 69, 72; Wilson, E.D., et al (1950), Arizona zinc and lead deposits, part I, AZ Bur. Mines Bull. 156: 138-142; Lang & Eastoe Econ Geol (1988) 83:551-567.;Econ Geol (1989) 84:650-662.
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Locality Updated: Woodsboro, Frederick Co., Maryland, USAFrom Bill Cordua, 13th Dec 2013 02:30:58