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Edwin H. McKee

Publications and source records attributed to Edwin H. McKee.

At least 37 records · Page 2Linked to original sources
USGS1999

Digital Geologic Map of the Nevada Test Site and Vicinity, Nye, Lincoln, and Clark Counties, Nevada, and Inyo County, California

This digital geologic map of the Nevada Test Site (NTS) and vicinity, as well as its accompanying digital geophysical maps, are compiled at 1:100,000 scale. The map compilation presents new polygon (geologic map unit contacts), line (fault, fold axis, metamorphic isograd, dike, and caldera wall) and point (structural attitude) vector data for the NTS and vicinity, Nye, Lincoln, and Clark Counties, Nevada, and Inyo County, California. The map area covers two 30 x 60-minute quadrangles-the Pahute Mesa quadrangle to the north and the Beatty quadrangle to the south-plus a strip of 7.5-minute quadrangles on the east side-72 quadrangles in all. In addition to the NTS, the map area includes the rest of the southwest Nevada volcanic field, part of the Walker Lane, most of the Amargosa Desert, part of the Funeral and Grapevine Mountains, some of Death Valley, and the northern Spring Mountains. This geologic map improves on previous geologic mapping of the same area (Wahl and others, 1997) by providing new and updated Quaternary and bedrock geology, new geophysical interpretations of faults beneath the basins, and improved GIS coverages. Concurrent publications to this one include a new isostatic gravity map (Ponce and others, 1999) and a new aeromagnetic map (Ponce, 1999).

Open-File Report↗
USGS1998

Evaluation of faults and their effect on ground-water flow southwest of Frenchman Flat, Nye and Clark counties, Nevada: a digital database

Ground-water flow through the region south and west of Frenchman Flat, in the Ash Meadows subbasin of the Death Valley ground-water flow system, is controlled mostly by faults which arrange the distribution of permeable and impermeable rocks. In addition, most permeability is along fractures caused by faulting in carbonate rocks. Large faults are more likely to reach the potentiometric surface as deep as 325 meters below the ground surface and are more likely to effect the flow path than small faults. This study concentrated on identifying large faults, especially where they cut carbonate rocks. Small faults, however, may develop as much permeability as large faults if they are penetrative and are part of an anastomosing fault_zone. The overall pattern of faults and joints at the ground surface in the Spotted and Specter Ranges is an indication of the fracture system at the depth of the water table. Most of the faults in these ranges are west-southwest-striking, high-angle faults, 100 to 3,500 meters long, with 10 to 300 meters of displacement. Many of them, such as those in the Spotted Range and Rock Valley are left-lateral strike-slip faults that are conjugate to the NW-striking right-lateral faults of the Las Vegas Valley shear zone. These faults control the ground-water flow path, which runs west-southwest beneath the Spotted Range, Mercury Valley and the Specter Range. The Specter Range thrust is a significant geologic structure with respect to ground- water flow. This regional thrust fault emplaces siliceous clastic strata into the north central and western parts of the Specter Range. These rocks act as a barrier that confines ground- water flow to the southern part of the range, directing it southwestward toward springs at Ash Meadows. These siliceous clastic aquitard rocks and overlying Cenozoic deposits probably also block westward flow of ground-water in Rock Valley, diverting it southward to the flow path beneath the southern part of the Specter Range.

Nevada↗
USGS1982

Preliminary report on the geology and gold mineralization of the Gold Basin-Lost Basin mining districts, Mohave County, Arizona

The Gold Basin-Lost Basin mining districts are adjacent to each other in northwestern Arizona, south of Lake Mead, and just west of the Grand Wash Cliffs. Most recorded production from lode deposits is credited to mines in the Gold Basin district, which is in the southern White Hills, whereas the bulk of the placer production has been from placers worked along the eastern flank of the Lost Basin range, about 16 km to the northeast across Hualapai Valley. Gold in quartz veins apparently was first discovered in the 1870's. Recorded production from the districts between 1901 and 1942 includes 13,508 oz gold and 6,857 oz silver, and this recorded production has a dollar value of about $359,000 of which 98 percent is credited to gold. Most known occurrences of lode gold in the districts are associated with widespread quartz-cored pegmatite-vein systems, presumably emplaced episodically during Proterozoic X, Proterozoic Y, and Late Cretaceous time into Proterozoic X metamorphic and igneous rocks. The bulk of the veins apparently were emplaced during the Late Cretaceous, and they were localized along both high- and low-angle structures in the Proterozoic X terrane. These veins appear to be associated genetically with presumably Late Cretaceous, two-mica magmatism. A Late Cretaceous two-mica monzogranite crops out in an approximately 4 to 5 km 2 area in the southern part of the Gold Basin district and includes some facies of episyenite. Some gold is found also in small episyenitic alteration pipes, or in veins caught up tectonically along a regionally extensive, low-angle detachment surface which crops out prominently in the southern White Hills, and has been traced for at least 30 km along the western flank of the White Hills. Hydrothermal micas from selected veins in the districts give K-Ar ages of 822, 712, 69, 68, and 65 m.y. (million years), and from the pipes, ages of 130 and 127 m.y. The oldest ages (822 and 712 m.y.) presumably reflect resetting of veins that probably were emplaced penecontemporaneous with emplacement of the 1,400-m.y. granite of Gold Butte, which crops out just to the north of Lake Mead. The latter ages (130 and 127 m.y.) must reflect either the presence of excess radiogenic argon in the hydrothermal environment of the evolving pipes, or contamination of the dated mineral separates by Proterozoic mica and (or) feldspar. Primary white mica from the two-mica monzogranite gives a K-Ar age of 72 m.y.. Most occurrences of gold in the veins and pipes probably reflect either remobilization of gold from gold-bearing, near-surface Proterozoic source areas, or anatectic incorporation of gold into Late Cretaceous, two-mica magmas from very deep gold-bearing Proterozoic sources. Deposition of gold occurred in a mesothermal environment during the galena-, chalcopyrite-, ferroan-carbonate-bearing stages of the veins. Homogenization studies of fluid inclusions prominent in the veins and pipes yield temperatures mostly in the range 150 to 280°C. Early-stage, trapping temperatures at the pipes probably were about 330°C and pressures in the range 500 to 700 bars can be inferred. Fluids were moderately saline, mostly 4 to 16 weight percent NaC1 equivalent, nonboiling, and also contain appreciable amounts of carbon dioxide and, in places, fluorine. Such fluids associated with the deposition of gold in these districts largely bridge the fluid composition interval between many other epithermal precious-metal and porphyry coper deposits. Approximately 350 compositional analyses obtained from native-gold samples from 20 mines in the Gold Basin district and 48 veins in the Lost Basin district show silver contents that range from 6 to approximately 50 weight percent, and copper from 0.01 to 0.5 weight percent. Metal zonation and possible relation to a porphyry copper system at depth can be inferred from some of these chemical data. The differences in the composition of placer gold from 24 occurrences in the Lost Basin district from that of nearby lode sources suggest that other sources contributed gold to the placers or that locally derived grains were enriched by oxidation and weathering of the lodes.

Arizona↗
USGS1975

Geothermal significance of eastward increase in age of upper Cenozoic rhyolitic domes in southeastern Oregon

Rhyolitic domes, flows, and ash-flow tuffs of Miocene to Holocene age form an important part of the thick sequence of Cenozoic volcanic rocks that cover southeastern Oregon east of the Cascade Range. Rhyolitic domes 11-17 m.y. old are widespread, particularly in the easternmost part of the state and in adjacent parts of Idaho and Nevada. Domes younger than 11 m.y. occur principally in two 250-km-long belts that trend N. 75° W. On the basis of 47 K/Ar radiometric dates, the rhyolitic domes in and between these belts show a remarkably well defined monotonic age progression from less than 1 m.y. old in the west to about 10 m.y. old on the east. The progression in age of the domes is sufficiently well defined that the ages of the domes can be smoothly contoured and the age of most undated domes can be estimated to within 1 m.y. The age contours are oblique to the trend of the two belts; domes younger than 4 m.y. occur only in and near the northern belt. The rate of progression is about 1 cm/yr for domes younger than about 5 m.y. and 3 cm/yr for domes 5-10 m.y. old. The change in rate of progression about 5 m.y. ago is accompanied by a change in orientation of the age contours and in area of outcrop. Inferred vents for dated rhyolitic ash-flow tuffs younger than 10 m.y. are located in areas where domes are approximately the same age as the tuffs and thus also fit the age progression. Most electric-power-producing geothermal fields in the world occur in or proximal to areas of young silicic volcanic rocks. On the basis of the well-defined age progression of rhyolitic domes in southeastern Oregon, silicic intrusive bodies sufficiently young to be heat sources for geothermal systems are likely only in the vicinity of Newberry Volcano at the west end of the northern belt of domes.

Oregon↗
USGS1973

Reconnaissance study of the strontium isotopic composition of Cenozoic volcanic rocks in the northwestern Great Basin

Sixteen mafic and intermediate lava flows of Eocene to Pleistocene age from the northwestern Great Basin have initial Sr 87 /Sr 86 ratios of from 0.7029 to 0.7047. Seven upper Miocene mafic and intermediate lava flows have initial ratios of from 0.7037 to 0.7041, suggesting a common source for the Steens Basalt and contemporaneous rocks of the northwestern Great Basin. Values of 0.7047 and 0.7033 obtained on olivine basalts of early Miocene and Quaternary ages, respectively, suggest that these lavas were derived from different source materials than were the late Miocene rocks. Unusually low values of 0.7029 obtained on two specimens of andesite from the Eocene Cedarville Series of Russell (1928) suggest that these lava flows were derived from still another source material. Ten silicic volcanic rocks, most from widespread and voluminous ash-flow sheets and lava complexes, have initial ratios of approximately 0.7023 to 0.7057. Some of the more radiogenic values, obtained on very highly differentiated and strontium-poor rock units, provide only an upper limit for the initial Sr 87 /Sr 86 ratios of the parent magmas. The close similiarity of the strontium isotopic composition of the silicic rocks to those of spatially and temporally associated intermediate lavas supports the concept that the widespread Miocene silicic volcanic rocks of the northwestern Great Basin were produced by the fractional crystallization of enormous volumes of mantle-derived mafic magma. The data also provide indirect support for the interpretation that the relatively radiogenic character of many salic volcanic rocks from other parts of the Great Basin largely reflects the presence of an unusually radiogenic mantle rather than the involvement of crustal material.

California, Idaho, Nevada, Oregon↗
USGS1973

Granitic rocks of the White Mountains area, California-Nevada: Age and regional significance

Potassium-argon ages have been determined on 25 biotite and hornblende samples (four coexisting biotite-hornblende pairs were dated) from a number of granitic formations in the more than 500 sq mi of dominantly granitic outcrop in the White Mountains. These new data, together with earlier published radiometric ages, indicate a group of plutons about 70 to 85 m.y. old, a single body about 210 m.y. old, another that may be about 225 m.y. old, and several between 130 and 185 m.y. old. Evidence of intrusion is lacking in the intervals of about 90 to 130 m.y. and 185 to 200 m.y. The oldest age, about 226 m.y., may represent the chance preservation of a “primary” hornblende in a body in which the dark minerals are largely recrystallized and their radiometric ages reset. This age suggests that Triassic magmatism may be more widespread along the eastern margin of the Sierra Nevada batholith than had previously been considered. The radiometric age data from the White Mountains, together with similar data from northwestern and north-central Nevada and abundant data from the central Sierra Nevada, suggest essentially continuous, albeit irregular, magmatic activity from Triassic to the end of Cretaceous, except for periods of little or no activity in earliest Jurassic and earliest Cretaceous. Episodes of magmatic activity may, and probably do, characterize specific areas, but when sufficiently large blocks of the Sierra Nevada batholith are considered, the sum of the episodes approaches a continuum.

California, Nevada↗
USGS1971

Age and chemistry of tertiary volcanic rocks in north-central Arizona and relation of the rocks to the Colorado Plateaus

During late Miocene (14.8 m.y.) to early Pliocene (10.1 m.y.) time, local latite and widespread basaltic flows accumulated with associated continental sedimentary deposits in north-central Arizona. Some of these rocks were displaced and tilted by normal faults, and new drainage, now occupied in part by basalt flows of late Pliocene age (average 5 m.y., maximum of 6 m.y.), was established at the southern margin of the Colorado Plateaus. The time of faulting and uplift of the Colorado Plateaus in this region is thus bracketed between about 10.1 and 6 m.y. ago. Five analyzed basalts fall within the tholeiitic basalt field of the alkali-silica diagram and twenty are in the alkalic basalt field; in general, they are similar to other alkali-olivine basalts from the western United States.

Arizona↗
USGS1971

Mesozoic granitic rocks in northwestern Nevada: A link between the Sierra Nevada and Idaho batholiths

Extensive areas in northwestern Nevada are underlain by granodiorite and quartz monzonite plutons, as well as less common smaller bodies of quartz diorite. Twenty-six K/Ar age determinations on rocks from this suite range from about 175 to 85 m.y., but most of the plutons are between 105 and 85 m.y. old. This Late Cretaceous intrusive epoch extending from 105 to 85 m.y. ago is here named the Lovelock intrusive epoch. Twenty-three whole-rock chemical analyses show that the granitic rocks of northwestern Nevada form a homogeneous differentiation series with a narrow range in major element distribution. The granitic plutons of northwestern Nevada are chemically and petrographically indistinguishable from granitic intrusives of equivalent age in the Sierra Nevada and Idaho batholiths, and form a link between these two major batholiths.

California, Idaho, Nevada↗
USGS1971

Tertiary igneous chronology of the Great Basin of western United States — Implications for tectonic models

The chronology of igneous activity in the Great Basin of western United States is used as a time framework for a simple plate model. This chronology suggests that a plate (Farallon plate) became underthrust to sufficient depth by the middle Tertiary to trigger the eruption of volcanic rocks of andesitic to rhyolitic composition in the central part of the Great Basin, 40 m.y. ago. This plate continued to be underthrust until about 19 m.y. ago, at which time it was completely consumed and volcanic activity ceased. When the oceanic ridge reached a certain point under the Great Basin about 16 m.y. ago, this resulted in the widespread eruption of olivine basalt and the main initial phase of Basin and Range faulting.

Arizona, California, Idaho, Nevada, Oregon, Utah↗