Additions to Bibliographies for Metallic Mineral Districts in Cochise, Graham, Greenlee, La Paz, Mohave, Pima, Santa Cruz, and Yuma Counties, Arizona
KeywordsArizona Geological Survey Open File Reports
Santa Cruz County
La Paz County
Metallic mineral districts
metallic mineral districts
MetadataShow full item record
CitationWelty, J.W., 1988, Additions to Bibliographies for Metallic Mineral Districts in Cochise, Graham, Greenlee, La Paz, Mohave, Pima, Santa Cruz, and Yuma Counties, Arizona. Arizona Geological Survey Open File Report, OFR-88-22, 36 p.
DescriptionThis report is an update to already published county metallic mineral district bibliographies for Cochise, Graham, Greenlee, La Paz, Mohave, Pima, Santa Cruz, and Yuma Counties (Schnabel and Welty, 1986a,b; and Schnabel and others 1986). In a mineral district classification, known metallic mineral occurrences are grouped according to geologic and metallogenic criteria rather than the geographic associations used in the traditional mining-district (Keith and others, 1983a,b). Ideally, a mineral district should consist of mineral occurrences that have a common genesis. A mineral-district classification is especially useful for understanding the geologic setting of mineralization and the distribution of known mineral occurrences with similar geologic settings. A mineral-district map, however, is by no means a statement of mineral potential because future discoveries within and outside established districts will affect district boundaries. Although understanding the distribution of known mineral deposits is essential in evaluating mineral potential, many other geologic and technologic factors must also be considered (Fellows, 1984).
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A GEOCHEMICAL STUDY OF ALTERATION AND MINERALIZATION IN THE WALLAPAI MINING DISTRICT, MOHAVE COUNTY, ARIZONA (MINERAL PARK, FLUID INCLUSIONS, SULFUR ISOTOPES).Lang, James Robert, 1961- (The University of Arizona., 1986)
THE DISTRIBUTION OF ALTERATION AND MINERALIZATION ASSEMBLAGES OF THE MINERAL PARK MINE, MOHAVE COUNTY, ARIZONAWilkinson, William Holbrook (The University of Arizona., 1981)The Mineral Park mine is a porphyry copper-molybdenum deposit developed within and adjacent to a Laramide quartz monzonite porphyry stock which intrudes Precambrian rocks in northwestern Arizona. The Precambrain sequence consists of older, broadly folded metasedimentary and metavolcanic rocks which were intruded by a 1700-1800 m.y. old granite gneiss batholith. The contact between the two Precambrian terranes is a major structural element in the district and appears to have been important in localizing the Laramide intrusions and mineralization. Alteration is defined by early pervasive biotitization of hornblende in the Precambrain rocks and by recrystallization of rock biotite in the quartz monzonite porphyry. Pervasively biotitized rocks are crosscut first by biotite and then by K-feldspar veinlets. Fracture-controlled, economic sulfide mineralization then began with quartz-molybdenite-K-feldspar-anhydrite and was followed by quartz-chalcopyrite-K-feldspar-anhydrite. This potassic alteration and accompanying mineralization occur throughout the deposit and are crosscut by later quartz-pyrite-sericite veinlets. Orientations of mineralized fractures evolved through time from EW during molybdenum mineralization to NW during quartz-pyrite-sericite mineralization. Fracture densities during molybdenum mineralization averaged 0.05 cm⁻¹ and increased to 0.14 cm⁻¹ during quartz-pyrite-sericite mineralization. Sulfides were deposited from low salinity fluids (0.5 - 2.0 molal) in the temperature range 330°-360°C. High salinity fluids occurred only with quartz that was earlier than sulfide deposition. No homogenization temperatures greater than 440°C were observed. Molybdenum mineralization cuts all rock types and defines a vertical cylinder with a distinct low-grade core. Ore grade molybdenum mineralization is equally distributed between Laramide and Precambrian rocks, and overall grade decreases with depth. Hypogene copper mineralization has a greater lateral distribution than molybdenum mineralization, and surrounds a low grade core coincident with the low grade molybdenum core. The distribution of alteration and mineralization assemblages and the fact that both of these features crosscut all exposed rock types suggest that copper-molybdenum mineralization was not temporally related to the quartz monzonite porphyry exposed in the mine area. The narrow range of homogenization temperatures observed and the lack of high homogenization temperatures compared with the results of computer modelled systems indicate formation of mineralization 2 to 3 km above a source intrusion. Because no evidence for boiling was observed, only minimum pressures of formation can be determined. Minimum pressures during sulfide deposition varied from 180 to 80 bars. These pressures correspond to minimum depths of formation of 2 to 3 km which is in good agreement with an inferred depth of burial of approximately 3 km based on stratigraphy restored from the adjacent Colorado Plateau.