Field Guide to the Black Pearl Tungsten Mine Area, Yavapai County, Arizona
Published:January 01, 1987
- PDF LinkChapter PDF
Christopher Schmitz, Donald M. Burt, 1987. "Field Guide to the Black Pearl Tungsten Mine Area, Yavapai County, Arizona", Proterozoic Ore Deposits of the Southwestern U.S., Ed DeWitt
Download citation file:
Wolframite-bearing quartz veins that have peripheral greisen-type wall rock alteration products are present in and around the Black Pearl mine (about 18 km northeast of Bagdad, Arizona). The veins are spatially related to a small albitite stock, and the largest vein, which was the only one mined, is at the apex of the stock. On the basis of field relations, this stock is interpreted to be a late differentiate related to the 1400 Ma Lawler Peak Granite, which crops out within 3 km of the mine. Other, similar albitite bodies are common in the Black Pearl mine area. Sharp contacts with country rocks (schist, monzogranite, and granodiorite), relatively unaltered xenoliths, and consistent mineralogy throughout indicate that the albitite bodies are igneous, and have undergone relatively minor postmagmatic alteration.
A thin (1- to 2-m-wide) border pegmatite unit (“stockscheider”) exists at the contact of the albitite of the Black Pearl mine and the country rock. Directional indicators and other evidence indicate that the pegmatite was formed from a volatile-rich phase at the time of magma emplacement. The sudden change from potassium-feldspar-rich pegmatite to fine-grained albitite suggests a pressure-quench of the system, perhaps owing to fracturing of and escape of volatiles up the Black Pearl vein at the apex of the stock. Similar stockscheider textures are typical of the borders of productive plutons in tungsten and tin districts worldwide.
Figures & Tables
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.