Geology topics

Research about Bodie Hills

Source-linked reports with geographic coverage including Bodie Hills.

3 recordsLinked to original sources

USGS2015

Gold-silver mining districts, alteration zones, and paleolandforms in the Miocene Bodie Hills Volcanic Field, California and Nevada

The Bodie Hills is a ~40 by ~30 kilometer volcanic field that straddles the California-Nevada state boundary between Mono Lake and the East Walker River. Three precious metal mining districts and nine alteration zones are delineated in Tertiary-Quaternary volcanic and Mesozoic granitic and metamorphic rocks that comprise the volcanic field. Cumulative production from the mining districts, Bodie, Aurora, and Masonic, is 3.4 million ounces of gold and 28 million ounces of silver. Small amounts of mercury were produced from the Potato Peak, Paramount-Bald Peak, and Cinnabar Canyon-US 395 alteration zones; a native sulfur resource in the Cinnabar Canyon-US 395 alteration zone has been identified by drilling. There are no known mineral resources in the other six alteration zones, Red Wash-East Walker River, East Brawley Peak, Sawtooth Ridge, Aurora Canyon, Four Corners, and Spring Peak. The mining districts and alteration zones formed between 13.4 and 8.1 Ma in predominantly ~15–9 Ma volcanic rocks of the Bodie Hills volcanic field. Ages of hydrothermal minerals in the districts and zones are the same as, or somewhat younger than, the ages of volcanic host rocks. Based on volcanic stratigraphy, geochronology, remnant paleosurfaces, and paleopotentiometric surfaces in mining districts and alteration zones, present landforms in the Bodie Hills volcanic field reflect incremental construction of stratovolcanoes and large- to small-volume flow-domes, magmatic inflation, and fault displacements. Landform evolution began with construction of the 15–13 Ma Masonic and 13–12 Ma Aurora volcanic centers in the northwestern and northeastern parts of the field, respectively. Smaller volcanoes erupted at ~11–10 Ma in, between, and south of these centers as erosional detritus accumulated north of the field in Fletcher Valley. Distally sourced, 9.7–9.3 Ma Eureka Valley Tuff filled drainages and depressions among older volcanoes and was partly covered by nearly synchronous eruptives during construction of four large 10–8 Ma volcanoes, in the southern part of the field. The lack of significant internal fault displacement, distribution of Eureka Valley Tuff, and elevation estimates derived from floras, suggest that the Bodie Hills volcanic field attained present elevations mostly through volcano construction and magmatic inflation, and that maximum paleoelevations (>8,500 ft) at the end of large volume eruptions at ~8 Ma are similar to present elevations.

California, Nevada↗

USGS2015

Geochronology of Cenozoic rocks in the Bodie Hills, California and Nevada

The purpose of this report is to present geochronologic data for unaltered volcanic rocks, hydrothermally altered volcanic rocks, and mineral deposits of the Miocene Bodie Hills and Pliocene to Pleistocene Aurora volcanic fields of east-central California and west-central Nevada. Most of the data presented here were derived from samples collected between 2000–13, but some of the geochronologic data, compiled from a variety of sources, pertain to samples collected during prior investigations. New data presented here (tables 1 and 2; Appendixes 1–3) were acquired in three U.S. Geological Survey (USGS) 40 Ar/ 39 Ar labs by three different geochronologists: Robert J. Fleck (Menlo Park, CA), Lawrence W. Snee (Denver, CO), and Michael A. Cosca (Denver, CO). Analytical methods and data derived from each of these labs are presented separately. The middle to late Miocene Bodie Hills volcanic field (BHVF) is a large (>700 km 2 ), long-lived (~9 million years [m.y.]), episodic eruptive complex (John and others, 2012) in the southern segment of the ancestral Cascades arc (du Bray and others, written commun., 2015) north of Mono Lake and east of Bridgeport, California (fig. 1). The field is near the west edge of the Walker Lane and the northwest edge of the Mina deflection where structures related to these shear zones may have localized magmatism. The Walker Lane (fig. 1) is a broad, northwest-striking zone of right-lateral shear that accommodates right-lateral motion between the Pacific and North America plates; the Mina deflection constitutes a 60-km-long right step in the Walker Lane (Faulds and Henry, 2008; Oldow, 1992, 2003; Stewart, 1988). The Bodie Hills volcanic field includes at least 31 volcanic rock units erupted from 21 significant volcanic eruptive centers. Four trachyandesite stratovolcanoes developed along the margins of the volcanic field and numerous silicic trachyandesite to rhyolite flow dome complexes erupted more centrally. Volcanism in the Bodie Hills volcanic field peaked at two periods, ~15.0 to 12.6 million years before present (Ma) and ~9.9 to 8.0 Ma, which were dominated by emplacement of large stratovolcanoes and large silicic trachyandesite-dacite lava domes, respectively. A final period of small-volume silicic dome emplacement began in the western part of the volcanic field at ~6 Ma and culminated at ~5.5 Ma (John and others, 2012).

California, Nevada↗

USGS2015

Geologic map of the Bodie Hills, California and Nevada

The Bodie Hills covers about 1,200 km 2 straddling the California-Nevada state boundary just north of Mono Lake in the western part of the Basin and Range Province, about 20 km east of the central Sierra Nevada. The area is mostly underlain by the partly overlapping, middle to late Miocene Bodie Hills volcanic field and Pliocene to late Pleistocene Aurora volcanic field (John and others, 2012). Upper Miocene to Pliocene sedimentary deposits, mostly basin-filling sediments, gravel deposits, and fanglomerates, lap onto the west, north, and east sides of the Bodie Hills, where they cover older Miocene volcanic rocks. Quaternary surficial deposits, including extensive colluvial, fluvial, glacial, and lacustrine deposits, locally cover all older rocks. Miocene and younger rocks are tilted ≤30° in variable directions. These rocks are cut by several sets of high-angle faults that exhibit a temporal change from conjugate northeast-striking left-lateral and north-striking right-lateral oblique-slip faults in rocks older than about 9 Ma to north- and northwest-striking dip-slip faults in late Miocene rocks. The youngest faults are north-striking normal and northeast-striking left-lateral oblique-slip faults that cut Pliocene-Pleistocene rocks. Numerous hydrothermal systems were active during Miocene magmatism and formed extensive zones of hydrothermally altered rocks and several large mineral deposits, including gold- and silver-rich veins in the Bodie and Aurora mining districts (Vikre and others, in press).

California, Nevada↗