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Uranium Potential and Geology of the Challis Volcanics of the Basin Creek-Yankee Fork Area, Custer County, Idaho: Final Report, Plate 1-5

Description: Appendices containing supplementary geological data of the Basin Creek-Yankee Fork area, including radioactivity measurements, locations of geochemical samples, and locations of paleomagnetic measurements to accompany a report on U.S. uranium resources in Custer County, Idaho.
Date: March 1979
Creator: Siems, Peter L.; Albers, Doyle F.; Malloy, Robert W.; Mitchell, Victoria E. & Perley, Philip C.
Partner: UNT Libraries Government Documents Department

Uranium Potential and Geology of the Challis Volcanics of the Basin Creek-Yankee Fork Area, Custer County, Idaho: Final Report

Description: From objectives: The principal objective of this work is to determine those areas that are favorable for concealed uranium deposits beneath the Challis Volcanic rocks in the area north of the Stanley Basin and south of the West Fork of Yankee Fork.
Date: March 1979
Creator: Siems, Peter L.; Albers, Doyle F.; Malloy, Robert W.; Mitchell, Victoria E. & Perley, Philip C.
Partner: UNT Libraries Government Documents Department

Intracaldera volcanism and sedimentation - Creede Caldera, Colorado

Description: Within the Creede caldera, Colorado, many of the answers to its postcaldera volcanic and sedimentary history lie within the sequence of tuffaceous elastic sedimentary rocks and tuffs known as the Creede Formation. The Creede Formation and its interbedded ash deposits were sampled by research coreholes Creede 1 and 2, drilled during the fall of 1991. In an earlier study of the Creede Formation, based on surface outcrops and shallow mining company coreholes, Heiken and Krier concluded that the process of caldera structural resurgence was rapid and that a caldera lake had developed in an annulus ({open_quotes}moat{close_quotes}) located between the resurgent dome and caldera wall. So far we have a picture of intracaldera activity consisting of intermittent hydrovolcanic eruptions within a caldera lake for the lower third of the Creede Formation, and both magmatic and hydrovolcanic ash eruptions throughout the top two-thirds. Most of the ash deposits interbedded with the moat sedimentary rocks are extremely fine-grained. Ash fallout into the moat lake and unconsolidated ash eroded from caldera walls and the slopes of the resurgent dome were deposited over stream delta distributaries within relatively shallow water in the northwestern moat, and in deeper waters of the northern moat, where the caldera was intersected by a graben. Interbedded with ash beds and tuffaceous siltstones are coarse-grained turbidites from adjacent steep slopes and travertine from fissure ridges adjacent to the moat. Sedimentation rates and provenance for elastic sediments are linked to the frequent volcanic activity in and near the caldera; nearly all of the Creede Formation sedimentary rocks are tuffaceous.
Date: June 1, 1997
Creator: Heiken, G.; Krier, D. & Snow, M.G.
Partner: UNT Libraries Government Documents Department

Geochemical evidence for waning magmatism and polycyclic volcanism at Crater Flat, Nevada

Description: Petrologic and geochemical studies of basaltic rocks in the Yucca Mountain region are currently focused on understanding the evolution of volcanism in the Crater Flat volcanic field and the mechanisms of polycyclic volcanism at the Lathrop Wells volcanic center, the youngest center in the Crater Flat volcanic field. Geochemical and petrologic data indicate that the magma chambers which supplied the volcanic centers in Crater Flat became situated at greater crustal depths as the field evolved. Deep magma chambers may be related to a waning magma flux that was unable to sustain upper crystal magma conduits and chambers. Geochemical data from the Lathrop Wells volcanic center indicate that eruptive units identified from field and geomorphic relationships are geochemically distinct. The geochemical variations cannot be explained by fractional crystallization of a single magma batch, indicating that several magma batches were involved in the formation of the Lathrop Wells center. Considering the low magma flux in the Yucca Mountain region in the Quaternary, the probability of several magma batches erupting essentially simultaneously at Lathrop Wells in considered remote. It is more likely that the Lathrop Wells center was formed by a series of eruptions that took place over many thousands of years. The geochemical data from Lathrop Wells is consistent with the concept of a complex, polycyclic volcano, which was originally proposed based on geomorphic and soil-development data.
Date: December 31, 1991
Creator: Perry, F.V. & Crowe, B.M.
Partner: UNT Libraries Government Documents Department

Geochemistry of the Lathrop Wells volcanic center

Description: Over 100 samples have been gathered from the Lathrop Wells volcanic center to assess different models of basalt petrogenesis and constrain the physical mechanisms of magma ascent in the Yucca Mountain region. Samples have been analyzed for major and trace-element chemistry, Nd, Sr and Ph isotopes, and mineral chemistry. All eruptive units contain olivine phenocrysts, but only the oldest eruptive units contain plagioclase phenocrysts. Compositions of minerals vary little between eruptive units. Geochemical data show that most of the eruptive units at Lathrop Wells defined by field criteria can be distinguished by major and trace-element chemistry. Normative compositions of basalts at Lathrop Wells correlate with stratigraphic position. The oldest basalts are primarily nepheline normative and the youngest basalts are exclusively hypersthene normative, indicating increasing silica saturation with time. Trace-element and major-element variations among eruptive units are statistically significant and support the conclusion that eruptive units at Lathrop Wells represent separate and independent magma batches. This conclusion indicates that magmas in the Yucca Mountain region ascend at preferred eruption sites rather than randomly.
Date: March 1, 1996
Creator: Perry, F.V. & Straub, K.T.
Partner: UNT Libraries Government Documents Department

Preliminary geologic map of the Sleeping Butte volcanic centers

Description: The Sleeping Butte volcanic centers comprise two, spatially separate, small-volume (<0.1 km{sup 3}) basaltic centers. The centers were formed by mildly explosive Strombolian eruptions. The Little Black Peak cone consists of a main scoria cone, two small satellitic scoria mounds, and associated lobate lava flows that vented from sites at the base of the scoria cone. The Hidden Cone center consists of a main scoria cone that developed on the north-facing slope of Sleeping Butte. The center formed during two episodes. The first included the formation of the main scoria cone, and venting of aa lava flows from radial dikes at the northeast base of the cone. The second included eruption of scoria-fall deposits from the summit crater. The ages of the Little Black Peak and the Hidden Cone are estimated to be between 200 to 400 ka based on the whole-rock K-Ar age determinations with large analytical undertainty. This age assignment is consistent with qualitative observations of the degree of soil development and geomorphic degradation of volcanic landforms. The younger episode of the Hidden Cone is inferred to be significantly younger and probably of Late Pleistocene or Holocene age. This is based on the absence of cone slope rilling, the absence of cone-slope apron deposits, and erosional unconformity between the two episodes, the poor horizon- development of soils, and the presence of fall deposits on modern alluvial surfaces. Paleomagnetic data show that the centers record similar but not identical directions of remanent magnetization. Paleomagnetic data have not been obtained for the youngest deposits of the Hidden Cone center. Further geochronology, soils, geomorphic, and petrology studies are planned of the Sleeping Butte volcanic centers 20 refs., 3 figs.
Date: July 1, 1991
Creator: Crowe, B.M. & Perry, F.V.
Partner: UNT Libraries Government Documents Department

Geological and geophysical signatures of the Jemez lineament: a reactivated Precambrian structure

Description: The Jemez lineament (N52/sup 0/E) is one of several northeast-trending lineaments that traverse the southwestern United States. It is defined by a 500-km-long alignment of late Cenozoic volcanic fields extending southwest from at least the Jemez Mountains in the north-central New Mexico to the San Carlos-Peridot volcanic field in east-central Arizona. Geochronologic data from Precambrian basement rocks indicate that the lineament is approximately coincident with a boundary between Precambrian crustal provinces. Characteristics of the lineament are high heat flow (>104.5 mW/m/sup 2/), an attenuated seismic velocity zone from 25 to 140 km depth, and an upwarp of the crustal electrical conductor inferred from magnetotelluric studies. The high electrical conductivity is probably caused by the presence of interstitial magma in the rocks of the mid-to-upper crust. The average electical strike within the Precambrian basement is N60/sup 0/E, supporting a relationship between the Precambrian structural grain and the Jemez lineament. The geological and geophysical data suggest that the lineament is a structural zone that extends deep into the lithosphere and that its location was controlled by an ancient zone of weakness in the Precambrian basement. Ages of late Cenozoic volcanic rocks along the lineament show no systematic geographic progression, thus indicating that a mantle plume was not responsible for the alignment of the volcanic fields.Most of the faults, dikes, and cinder cone alignments along the lineament trend approximately N25/sup 0/E and N5/sup 0/W. These trends may represent Riedel shears formed by left-lateral transcurrent movement along the structure. Less common trends of cinder cone alignments and dikes are approximately N65/sup 0/W and N85/sup 0/W. The diversity in orientation indicates that the magnitudes of the two horizontal principal stresses within the lineament have been approximately equal for at least the last 5 m.y.
Date: January 1, 1981
Creator: Aldrich, M.J. Jr.; Ander, M.E. & Laughlin, A.W.
Partner: UNT Libraries Government Documents Department

Calderas and mineralization: volcanic geology and mineralization in the Chianti caldera complex, Trans-Pecos Texas

Description: This report describes preliminary results of an ongoing study of the volcanic stratigraphy, caldera activity, and known and potential mineralization of the Chinati Mountains area of Trans-Pecos Texas. Many ore deposits are spatially associated with calderas and other volcanic centers. A genetic relationship between calderas and base and precious metal mineralization has been proposed by some and denied by others. Steven and others have demonstrated that calderas provide an important setting for mineralization in the San Juan volcanic field of Colorado. Mineralization is not found in all calderas but is apparently restricted to calderas that had complex, postsubsidence igneous activity. A comparison of volcanic setting, volcanic history, caldera evolution, and evidence of mineralization in Trans-Pecos to those of the San Juan volcanic field, a major mineral producer, indicates that Trans-Pecos Texas also could be an important mineralized region. The Chianti caldera complex in Trans-Pecos Texas contains at least two calderas that have had considerable postsubsidence activity and that display large areas of hydrothermal alteration and mineralization. Abundant prospects in Trans-Pecos and numerous producing mines immediately south of the Trans-Pecos volcanic field in Mexico are additional evidence that ore-grade deposits could occur in Texas.
Date: January 1, 1981
Creator: Duex, T.W. & Henry, C.D.
Partner: UNT Libraries Government Documents Department

The Use of Microearthquakes in Prospecting for Geothermal Areas and Magma Chambers

Description: Microearthquakes have been observed in nearly all major geothermal areas where detailed recordings have been made. These small earthquakes when recorded over a period of months are primarily confined within the geothermal areas. Such observations suggest that microearthquakes are an important part of those geothermal areas where sufficient heat transfer is taking place to allow economic production of geothermal power under present technology. These earthquakes seem to occur on the fracture systems that allow convection of heat to the surface. The tectonic stress shown by the earthquakes may be necessary to continue creating fresh surfaces for sufficient heat transfer. The strength of the rocks in major geothermal areas may also be reduced when the hot water leaches silica and other elements allowing the local tectonic stress to be released as small earthquakes. Whatever the explanation, studies of microearthquakes in major geothermal areas seem useful for trying to understand the subsurface structure of these areas and thus locating regions of convective heat transfer. Research in the US for locating magma chambers is still inadequate. Some evidence of magma chambers in the Katmai area of Alaska was reported by Kubota and Berg and Matumoto on the basis of earthquake locations, absence of some S-waves, and attenuation of high-frequency waves. Work on the unique Hawaiian volcanoes has failed so far to show clear seismic evidence of magma chambers even though deformation data imply that magma is stored at shallow depth in the summit and east rift areas. S-waves are not recorded sharply at most stations, and attenuation of high-frequency waves is observed in some areas. No significant gaps in earthquake distribution with depth have been clearly identified yet. Magma chambers in Hawaii may be plexuses of small conduits rather than large chambers. The studies of earthquake locations and lateral changes in seismic-wave attenuation ...
Date: January 1, 1974
Creator: Ward, Peter L. & Koyanagi, Robert
Partner: UNT Libraries Government Documents Department

Geothermal spas in Hawaii: A new tourist industry. : A preliminary report

Description: There are at least three very good uses for active volcanism: Obtain energy from it. Study it. Enjoy it. We are already obtaining electrical energy and industrial heat from Kilauea's abundant resource by drilling geothermal wells and building power plants. Our Volcano Observatory is recognized as a world renowned center of learning about volcanism. Our Volcanoes National Park allows us to view and appreciate this awesome phenomenon. For several years people have speculated about the high potential in Hawaii for another way of enjoying this warmth of mother earth -- spas or resorts that would make use of water that is naturally heated and mineralized by volcanic activity. However, before spas are developed in Hawaii, answers are needed to several important questions dealing with such topics as the suitability of our geothermal waters, sources of water that could be tapped, special equipment and materials needed, land availability, governmental and environmental hurdles, and the economics of this unique business. Though a considerable amount of research is still needed, it was felt worthwhile to summarize the information gathered to date from historical works, brochures, personal communications, and other sources. This report should stimulate interest in, and perhaps accelerate, the development of one of Hawaii's most important natural resources.
Date: July 1, 1987
Creator: Woodruff, J. L.
Partner: UNT Libraries Government Documents Department

Basaltic volcanic episodes of the Yucca Mountain region

Description: The purpose of this paper is to summarize briefly the distribution and geologic characteristics of basaltic volcanism in the Yucca Mountain region during the last 10--12 Ma. This interval largely postdates the major period of silicic volcanism and coincides with and postdates the timing of major extensional faulting in the region. Field and geochronologic data for the basaltic rocks define two distinct episodes. The patterns in the volume and spatial distribution of these basaltic volcanic episodes in the central and southern part of the SNVF are used as a basis for forecasting potential future volcanic activity in vicinity of Yucca Mountain. 33 refs., 2 figs.
Date: March 1, 1990
Creator: Crowe, B.M.
Partner: UNT Libraries Government Documents Department

Geology and geothermal resources of the Rexburg Area, eastern Idaho

Description: A brief description of major Cenozoic geologic features of the Rexburg area and a discussion of their geothermal significance are presented. The study area, identified as having geothermal potential, is approximately circular, about 55 km across, and centered on the town of Rexburg. It is roughly coextensive with a complex of about eight calderas of Pliocene age, here named the Rexburg caldera complex. These calderas were the source of several major rhyolitic volcanic deposits present along the southeast margin of the eastern Snake River Plain. The geology of this area was previously mapped in reconnaissance (Prostka and Hackman, 1974) and much of it as remapped in detail in 1977 because of its recognized geothermal potential.
Date: January 1, 1978
Creator: Prostka, H.J. & Embree, G.F.
Partner: UNT Libraries Government Documents Department

Inversion results of time-domain electromagnetic soundings near Medicine Lake, California, geothermal area

Description: A number of time-domain electromagnetic (TDEM) soundings were made in the vicinity of Medicine Lake, California, during July, 1982, as part of the US Geological Survey's geothermal research program. The objectives were to evaluate the use of TDEM methods in this environment, to compare frequency and time-domain results, and to study variations in the conductive layer (Zohdy and Bisdorf, 1982) which were known to exist in the area of the Medicine Lake volcano. The TDEM soundings were made at nine sites using both single and central loop configurations (Spies, 1980). At several of the sites, the large TDEM square loop (1500 ft. per side) was also used as a transmitter loop for loop-loop frequency domain soundings (Frischknecht, 1967). The frequency domain soundings have not been processed to-date; however, to make the data available, all TDEM results and their computer inversions are being presented in this preliminary report.
Date: January 1, 1983
Creator: Anderson, W.L.; Frischknecht, F.C.; Raab, P.V.; Bradley, J.A.; Turnross, J. & Buckley, T.W.
Partner: UNT Libraries Government Documents Department

Potential for hot-dry-rock geothermal resources: experimental results

Description: Hot dry rock (HDR) contains insufficient permeability and fluid for natural hydrothermal development, but water pumped in a circulation loop through a HDR reservoir (hydraulically fractured between two drill holes) is being tested and evaluated. The formation of such in situ heat transfer systems, and subsequent testing of the man-made geothermal reservoirs in the Jemez volcanic field, New Mexico have already indicated the technical feasibility of the hot dry rock (HDR) geothermal concept. Documented production history and heat-extraction data obtained during the period from 1978 to 1980 have confirmed heat transfer, low water loss, and predictable thermal drawdown models for the HDR systems. During a nine month test of closed-loop heat extraction operations, 15 x 10/sup 6/ kWh of thermal energy were produced. The effective heat-transfer area and volume of the reservoir increased due to secondary fracturing caused by thermal contraction of the reservoir rock, and sustained pressurization. Drilling, fracturing, and testing of a larger, hotter reservoir system is now underway on a HDR geothermal reservoir of commercial size.
Date: January 1, 1982
Creator: Rowley, J.C.; Heiken, G.; Murphy, H.D. & Kuriyagawa, M.
Partner: UNT Libraries Government Documents Department

Modeling of subsurface geology in Medicine Lake, California

Description: In this document we present the results of our analysis of data from 16 three-component seismometers and 8 dynamite explosions around the Medicine Lake volcano's Glass Mountain in northern California. The Medicine Lake volcano is located just northeast of the southeastward-trending Cascade Range of shield and small composite volcanoes. 2 refs., 6 figs.
Date: July 26, 1988
Creator: Rial, J.A. & Saltzman, N.
Partner: UNT Libraries Government Documents Department

Stratigraphy, petrology, and geochemistry of the Spurr Volcanic Complex, eastern Aleutian Arc, Alaska. [(Appendix for geothermal fluid chemistry)]

Description: The Spurr Volcanic Complex (SVC) is a calcalkaline, medium-K, sequence of andesites erupted over the last quarter of a million years by the easternmost currently active volcanic center in the Aleutian Arc. The ancestral Mt. Spurr was built mostly of andesites of uniform composition (58 to 60% SiO/sub 2/), although andesite production was episodically interrupted by the introduction of new batches of more mafic magma. Near the end of the Pleistocene the ancestral Mt. Spurr underwent Bezyianny-type avalanche caldera formation, resulting in the production of a volcanic debris avalanche with overlying ashflows. Immediately afterward, a large dome (the present Mt. Spurr) was emplaced in the caldera. Both the ashflows and dome are made of acid andesite more silicic than any analyzed lavas from the ancestral Mt. Spurr (60 to 63% SiO/sub 2/), yet contain olivine and amphibole xenocrysts derived from more mafic magma. The mafic magma (53 to 57% SiO/sub 2/) erupted during and after dome emplacement, forming proto-Crater Peak and Crater Peak. Hybrid pyroclastic flows and lavas were also produced. Proto-Crater Peak underwent glacial dissection prior to the formation of Crater Peak in approximately the same location. Appendices II through VIII contain a summary of mineral compositions; Appendix I contains geochemical data. Appendix IX by R.J. Motyka and C.J. Nye describes the chemistry of geothermal fluids. 78 refs., 16 figs., 3 tabs.
Date: December 1, 1987
Creator: Nye, C.J.
Partner: UNT Libraries Government Documents Department

Paleomagnetism of the Quaternary Cerro Prieto, Crater Elegante, and Salton Buttes volcanic domes in the northern part of the Gulf of California rhombochasm

Description: Deviating thermomagnetic directions in volcanics representing the second and fifth or sixth pulse of volcanism suggest that the Cerro Prieto volcano originated about 110,000 years B.P. and continued to be active intermittently until about 10,000 years ago.
Date: February 1, 1980
Creator: de Boer, J.
Partner: UNT Libraries Government Documents Department

{sup 40}Ar/{sup 39}Ar laser fusion and K-Ar ages from Lathrop Wells, Nevada, and Cima, California: The age of the latest volcanic activity in the Yucca Mountain area

Description: K-Ar and {sup 40}Ar/{sup 39}Ar ages from the Lathrop Wells volcanic center, Nevada, and from the Cima volcanic field, California, indicate that the recently reported 20-ka age estimate for the Lathrop Wells volcanic center is incorrect. Instead, an age of 119 {plus_minus} 11 to 141 {plus_minus} 10 ka is indicated for the Lathrop Wells volcanic center. This age corrected is concordant with the ages determined by two independent isotopic geochronometric techniques and with the stratigraphy of surficial deposits in the Yucca Mountain region. In addition, paleomagnetic data and radiometric age data indicate only two volcanic events at the Lathrop Wells volcanic center that are probably closely linked in time, not as many as five as recently reported. 32 refs., 2 figs., 2 tabs.
Date: May 1, 1991
Creator: Turrin, B.D. & Champion, D.E.
Partner: UNT Libraries Government Documents Department

The Lathrop Wells volcanic center: Status of field and geochronology studies

Description: The purpose of this paper is to describe the status of field and geochronology studies of the Lathrop Wells volcanic center. Our perspective is that it is critical to assess all possible methods for obtaining cross-checking data to resolve chronology and field problems. It is equally important to consider application of the range of chronology methods available in Quaternary geologic research. Such an approach seeks to increase the confidence in data interpretations through obtaining convergence among separate isotopic, radiogenic, and age-correlated methods. Finally, the assumptions, strengths, and weaknesses of each dating method need to be carefully described to facilitate an impartial evaluation of results. The paper is divided into two parts. The first part describes the status of continuing field studies for the volcanic center for this area south of Yucca Mountain, Nevada. The second part presents an overview of the preliminary results of ongoing chronology studies and their constraints on the age and stratigraphy of the Lathrop Wells volcanic center. Along with the chronology data, the assumptions, strengths, and limitations of each methods are discussed.
Date: March 1, 1992
Creator: Crowe, B.; Morley, R.; Wells, S.; Geissman, J.; McDonald, E.; McFadden, L. et al.
Partner: UNT Libraries Government Documents Department

The Timber Mountain magmato-thermal event: An intense widespread culmination of magmatic and hydrothermal activity at the southwestern Nevada volcanic field

Description: Eruption of the Rainier Mesa and Ammonia Tanks Members Timber Mountain Tuff at about 11.5 and 11.3 Ma, respectively, resulted in formation of the timber Mountain (TM) caldera; new K-Ar ages show that volcanism within and around the TM caldera continued for about 1 m.y. after collapse. Some TM age magmatic activity took place west and southeast of the TM caldera in the Beatty -- Bullfrog Hills and Shoshone Mountain areas, suggesting that volcanic activity at the TM caldera was an intense expression of an areally extensive magmatic system active from about 11.5 to 10Ma. Epithermal Au-Ag, Hg and fluorite mineralization and hydrothermal alteration are found in both within and surrounding the Timber Mountain -- Oasis Valley caldera complex. New K-Ar ages date this hydrothermal activity between about 13 and 10 Ma, largely between about 11.5 and 10 Ma, suggesting a genetic relation of hydrothermal activity to the TM magmatic system.
Date: May 1, 1988
Creator: Jackson, M.R. Jr.
Partner: UNT Libraries Government Documents Department