Cauldron subsidence of Oligocene age at Mount Lewis, northern Shoshone Range, Nevada
No abstract available.
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Geology topics
Research about Nevada
Source-linked reports with geographic coverage including Nevada.
Replacement barite deposit, southern Independence Mountains, Nevada
Allochthonous Devonian chert, metaquartzite, and greenstone in the Blue Basin quadrangle,, southern Independence Mountains, Nevada, are mineralized with barite forming a deposit of possible commercial grade and size. Textural evidence indicates that the barite was deposited in the host rocks principally by replacement, to a lesser extent by a process involving displacement and expansion of the host-rock material, and to a very minor extent by fracture filling.
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The Oligocene volcanic center at Eureka, Nevada
A volcanic center covering an area of about 80 km 2 near Eureka, Nev., and active in the early Oligocene, is characterized by rhyolitic, rhyodacitic. and andesitic pyroclastic rocks, lava flows, and shallow intrusive bodies. These rocks were emplaced as intertonguing and interpenetrative units during a 5-m.y. interval; most of the volcanism was in the last 3 million years of this period (36 to 33 m.y. ago).
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K-Ar Age Relations of Granodiorite Emplacement and Tungsten and Gold Mineralization near the Getchell Mine, Humboldt County, Nevada
A granodiorite stock intrudes complexly folded and thrust-faulted Paleozoic sedimentary rocks in the Osgood Mountains of eastern Humboldt County, Nevada. Within the metamorphic aureole surrounding the pluton, the sedimentary rocks are converted to cordierite hornfels and marble; tungsten-bearing tactites developed along the contacts of the granodiorite. Cutting the granodiorite and sedimentary rocks is the Getchell fault, along which the disseminated gold ore bodies of the Getchell mine are localized. K-Ar ages of the granodiorite, andesite porphyry, tungsten-bearing tactites, and altered granodiorite from the Getchell mine indicate that emplacement, alteration, and mineralization are all part of a magmatic-thermal episode which took place approximately 90 m.y. ago.
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Geodetic determination of strain at the Nevada Test Site following the Handley event
Repeated surveys of a trilateration network (aperture greater than 20 km) centered on ground zero for the HANDLEY event, a nuclear explosion at the Nevada Test Site with yield in excess of 1 megaton, suggest that the explosion induced an east-west extension of the network by more than 50 mm. In the year following the detonation, this deformation reversed such that the final configuration represented a small east-west contraction from the pre-HANDLEY state. In the subsequent 2-year period, only minor deformation was detected. Thus, the overall response of Pahute Mesa may be described as stable. The explosion-induced deformation is thought to be partly due to slip on faults driven by the large-amplitude seismic waves from the explosion. The mechanism of the postshot relaxation is not understood.
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Gravity map of the northern Nellis Air Force Bombing and Gunnery Range, Nevada
No abstract available.
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Geologic map of the Pinto Summit quadrangle, Eureka and White Pine Counties, Nevada
No abstract available.
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The chemical composition and estimated minimum thermal reservoir temperatures of the principal hot springs of northern and central Nevada
Fifty-five of the principal hot springs in northern and central Nevada have been sampled for chemical analyses. Major element constituents, sodium, potassium, calcium, and silica suggest minimum thermal-aquifer temperatures of 140°C or more at 16 of the hot spring complexes. At least five of the hot springs issue mixed waters which may indicate thermal-aquifer temperatures significantly lower than the true thermal-aquifer temperature. Sodium is the principal cation in almost all the spring waters. Four springs in northern Nye County and adjacent Eureka County have approximately equal amounts of sodium and calcium. Bicarbonate is the principal anion in most of the spring waters. However, the sampled hot springs on the western edge of the State have chloride as the principal anion. A diffuse zone of bicarbonate chloride waters with or without sulfate separates the chloride and bicarbonate regions.
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Water-resources data collected in the Devils Hole area, Nevada, 1973-74
The U.S. Geological Survey collected water-level, spring-flow, and power-consumption data in the Devils Hole area from July 1973 through June 1974. The work for this second annual data report was financed by the National Park Service. The work for the first annual, report (Larson, 1974) was financed jointly by the U.S. Bureau of Sport Fisheries and the U.S. Geological Survey. Continuous recorders were used to monitor water levels in Devils Hole, two observation wells, and the flow from four springs. Also, monthly readings were made on two wells to help define a general trend of ground-water levels. Also, monthly meter readings of six electrically powered irrigation wells provided a record of power consumption, which in turn is a measure of the amount of water pumped. The purpose of the work is to observe the effects of groundwater withdrawals for irrigation on the level in Devils Hole and the flow from the major springs in the area. The pool in Devis Hole, which is a collapsed fault structure, is the only known native habitat of desert pupfish, Cyprinodon diabolis.
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Water-resources data collected in the Devils Hole area, Nevada, 1972-1973
No abstract available.
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Geology and mineral deposits of Churchill County, Nevada
Churchill County, in west-central Nevada, is an area of varied topography and geology that has had a rather small total mineral production. The western part of the county is dominated by the broad low valley of the Carson Sink, which is underlain by deposits of Lake Lahontan. The bordering mountain ranges to the west and south are of low relief and underlain largely by Tertiary volcanic and sedimentary units. Pre-Tertiary rocks are extensively exposed east of the Carson Sink in the Stillwater Range, Clan Alpine Mountains, Augusta Mountains, and New Pass Mountains. The eastern valleys are underlain by Quaternary alluvial and lacustrine deposits contemporaneous with the western deposits of Lake Lahontan. The eastern mountain ranges are more rugged than the western ranges and have higher relief; the eastern valleys are generally narrower.
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Barium in hybrid granitoid rocks of the southern Snake Range, Nevada
In a magmatic environment, barium usually substitutes for potassium in the crystallizing silicates, and the two increase together in rocks late in the differentiation sequence. Results of this study show the opposite trend in an equivalent of a large part (63-76 percent SiO 2 ) of the classic differentiation sequence that resulted mainly from assimilation of chemically distinct host rocks. The barium content of the hybrid granitoid rock appears to be controlled mainly by the barium contents of the various sedimentary rock types assimilated.
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Stable isotope and lead isotope study of the Cortez, Nevada, gold deposit and surrounding area
Isotope studies of sulfur, carbon, hydrogen, oxygen, and lead were carried out to clarify the age and origin of the Cortex gold deposit and the surrounding mineralized area. The hydrogen isotope data indicate that meteoric water was the dominant component of the ore-forming fluids at Cortez. The hydrogen isotope data support geologic evidence for a Tertiary age for the deposit. The oxidation of the ore probably occurred during the deposition of postore calcite and was caused by waters whose oxygen isotopic composition was distinctly different from that of the ore fluids. The carbon isotope data suggest that the only carbon present in the ore fluids was derived from solution of the host rock. The lead and sulfur data are consistent with a possible sedimentary derivation for the gold in the ore. Lead and sulfur isotope distributions indicate that much of the galena mineralization in the area occurred during the Jurassic.
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Earthquake history of Nevada
Since 1852, more than 30 shocks of intensity VI or greater (Modified Mercalli scale) have occurred in western Nevada. At least three of these were classified as intensity X. In addition, seven earthquakes (intensity VI or greater) were centered in the eastern part of the State. Almost 2,000 other shocks have been cataloged in the nearly 125-year period of historical records. Thus, Nevada ranks among the most seismically active States.
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Paleozoic tectonics in the Edna Mountain quadrangle, Nevada
Geologic mapping at scale 1:24,000 of the Edna Mountain 15-minute quadrangle, Humboldt County, Nev., revealed two episodes of pre-Mesozoic deformation that are difficult to reconcile with either the Antler or the Sonoma orogeny. We believe that the older episode predated the Antler orogeny and may be as old as Late Cambrian. The younger episode may have been more localized, predated the Sonoma orogeny, and was probably Late Pennsylvanian to Permian in age. Deformation related to Antler and Sonoma orogenies also occurred. These four episodes suggest that cycles of uplift, folding, faulting, and erosion began early in the development of the southern Cordillera and continued intermittently throughout Paleozoic time. West of the continental shelf was a broad subsiding basin marked by narrow troughs and elongate structural highs which emerged, matured, and diminished at different times. Waxing and waning deformation in various parts of the geosyncline acting upon local "highs" and troughs can explain the seemingly erratic distribution in north-central Nevada of different fades of time-correlative stratigraphic units and structural blocks of Paleozoic age. Telescoping of facies by thrust faulting certainly took place, but large displacements within brief periods are not essential to the validity of the explanation.
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Thallium-bearing orpiment, Carlin gold deposit, Nevada
A variety of orpiment, As 2 S 3 , containing a significant amount of thallium has been identified in the unoxidized East ore body of the Carlin gold deposit. The mineral occurs in small veinlets with barite, calcite, quartz, and realgar.
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