Surface Excursions, Mountain Pass Area
Published:January 01, 1987
0.0 Drive north past abandoned gas station on the right and old bowling alley on the left.
0.2 Turn left on residential street. Just after left turn the road forks; stay to the left on North Park Road.
0.3 Take the left fork in the road, around a satellite television dish. Just past the satellite dish turn off the paved road and take the well-traveled dirt road to your left. This dirt road goes toward an active waste dump, but turns south at the base of the waste dump.
Follow the road around the south side of the waste pile, traveling west, parallel to the Interstate Highway on your left. The dumps on the right are some of the older waste piles at the mine and are no longer used because deep mining by open pit methods of the carbonatite beneath the waste piles would entail moving the dumps. The fence around the waste piles is the property boundary of Moly Corp. Inc.; we should not go inside the fenced area. Gray rocks on the dump are 1700 Ma high-grade metaigneous and metamorphic rocks. Tan rocks on the dump are 1700 Ma granite and 1400 Ma carbonatite material. Carbonatite on this dump averages less than 3 percent combined rare-earth oxides. When this waste dump was active the cutoff grade of ore at the mine averaged 5 percent rare-earth oxides; currently the cutoff grade of ore is approximately 9 percent rare-earth oxides.
0.9 Road turns to the right (north) around the
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.