Massive Sulfide Deposits at Bagdad, Arizona: End-Products of a Recurrent Early Proterozoic Volcanic Hydrothermal System
Published:January 01, 1987
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Thomas J. Connelly, Clay M. Conway, 1987. "Massive Sulfide Deposits at Bagdad, Arizona: End-Products of a Recurrent Early Proterozoic Volcanic Hydrothermal System", Proterozoic Ore Deposits of the Southwestern U.S., Ed DeWitt
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The Old Dick and Bruce massive sulfide deposits are hosted by a 3-km-thick Lower Proterozoic bimodal submarine volcanic sequence. Both deposits are at the contact between metabasalt flows and metamorphosed volcaniclastic strata of the Bridle Formation and overlying massive quartz porphyry of the Dick Rhyolite. Mixed metavolcanic and metamorphosed volcaniclastic rocks that may be part of the Butte Falls Tuff or Hillside Mica Schist overlie the Dick Rhyolite. Diverse, widespread, and locally intense hydrothermal premetamorphic alteration is spatially associated with massive sulfide mineralization is noted in both the Bridle Formation and in the Dick Rhyolite. Alteration patterns and chert suggest that hydrothermal activity was simultaneous with deposition of massive sulfide minerals and emplacement of the Bridle Formation. The recurrent, long-lived hydrothermal activity was probably driven by heat from synvolcanic mafic and felsic hypabyssal sills intruding the Bridle Formation. The delineation of previously unmapped hydrothermal alteration patterns stratigraphically beneath the Old Dick and Bruce deposits suggests a recurrent, metal-rich exhalative system that could be mineralized at different stratigraphic levels.
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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.