Early Proterozoic Gold Mineralization, Alteration Assemblages, and Geochemistry of the Huron-Montezuma Prospect, Yavapai County, Arizona
Published:January 01, 1987
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Patrick F. O'Hara, 1987. "Early Proterozoic Gold Mineralization, Alteration Assemblages, and Geochemistry of the Huron-Montezuma Prospect, Yavapai County, Arizona", Proterozoic Ore Deposits of the Southwestern U.S., Ed DeWitt
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Metavolcanic and metasedimentary rocks of the Yavapai Series (Anderson and Creasey, 1958) crop out within the area described in this study. These rocks were originally subdivided into the Ash Creek Group and Alder Group (Anderson and Blacet, 1972). Isotopic data led Anderson and others (1971) to replace the name Alder Group with the Big Bug Group, which includes all the rocks of the Yavapai Series exposed in the Prescott-Jerome area.
The Big Bug Group is divided into three formations. From oldest to youngest they are: 1) Green Gulch Volcanics; 2) Spud Mountain Volcanics; and 3) Iron King Volcanics (Anderson and Silver, 1976). The Green Gulch Volcanics are not present in the area of this study and will not be discussed. The thickness of the Big Bug Group cannot be measured with confidence because of the probability that unrecognized small folds on the flanks of major folds duplicate the section, and because of probable thinning and thickening of units during deformation (Anderson and Blacet, 1972c).
The Iron King Volcanics are composed of a thick sequence of metamorphosed, pillowed and amygdaloidal andesitic and basaltic flows. Locally the Iron King contains thin interbeds of metamorphosed rhyolitic tuff and flows units. The youngest part of the Iron King is a mixed metatuff of andesitic to rhyolitic composition that crops out in the trough of an overturned syncline.
The Iron King Volcanics have been informally subdivided into members (O'Hara, 1981; unpublished map) in order to facilitate mapping for industry. The area encompassing the Montezuma, Swindler
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Proterozoic Ore Deposits of the Southwestern U.S.
This field conference of the Society of Economic Geologists, held in conjunction with the 1987 Annual Meeting of the Geological Society of America in Phoenix, Arizona, investigates various Proterozoic ore deposits in southeastern California and western and central Arizona. The trip starts in Las Vegas, Nevada, and ends in Phoenix, Arizona. Although Proterozoic ore deposits and geology are emphasized, the field trip traverses a variety of tectonic provinces, each containing ore deposits of various ages. Many geologic features and ore deposits that are not Proterozoic in age will be discussed during the course of the trip, but no stops will be made to investigate any of these, features.
The morning part of the trip starts in the Mesozoic foreland fold and thrust belt of Nevada and southeastern California, goes just east of the Mesozoic batholith belt of California, and ends in crystalline basement containing Early and Middle Proterozoic metamorphic and plutonic rocks. Within this basement is exposed the Middle Proterozoic Mountain Pass Carbonatite deposit, the largest source of rare-earth elements in the world. The Mountain Pass Carbonatite will be the focus of our morning stops.
The afternoon part of the trip crosses Early Proterozoic high-grade metamorphic rocks and plutonic rocks east of Mountain Pass. Ore deposits noted along the afternoon portion of the trip include middle Tertiary epithermal, gold-rich veins at Searchlight, Nevada, and disseminated gold deposits in Tertiary volcanic rocks near Hart Peak in the New York Mountains. The trip continues across the Colorado River trough along the border of California and Arizona, where crystalline basement and its cover of Tertiary volcanic rocks and plutons have been greatly extended along listric normal faults and low-angle detachment faults. The afternoon part of the trip ends in Oatman, Arizona, a district famous for its middle Tertiary epithermal, gold-rich deposits. The ore deposits at Oatman will be the subject of a slide show and talk after supper on the first night of the trip.
The first day ends with an evening drive across a middle Tertiary volcanic pile near Oatman. The first night will be spent in Kingman, Arizona.
Assemble at the Las Vegas Convention Center, south of the Hilton Hotel. Take any main street south to Tropicana Avenue. Turn west on Tropicana, past the Las Vegas Strip, and continue to Interstate Highway 15. Turn south on Interstate 15 toward Mountain Pass, California. Mileage starts at 0.0.