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  • "A literature search found 46 geothermal f
    "A literature search found 46 geothermal fields for which reservoir temperatures in excess of 180degrees C have been proven by drilling and for which there is either drilling or geophysical data on which to base an estimate of field area. These fields are ranked according to area in Table 1 and their frequency distribution is shown in Fig. 2." "Sufficient information was found in the literature search to calculate an empirical value for the unit area power productivity for 18 of the 46 fields listed in Table 1. These values were calculated for each field by dividing total well productivities by the area occupied by the well field."
    s by the area occupied by the well field."  +
  • "A new geothermal system was identified fr
    "A new geothermal system was identified from 2m measurements at Emerson Pass on the Pyramid Lake Paiute Reservation in Washoe County, Nevada. This narrow NNW-trending valley contains several faults that appear to transfer dextral strain from NW-striking faults in the northern Walker Lane to N-NNW striking normal faults in the Smoke Creek Desert. The thermal anomaly extends for at least 3 km parallel to the range-front fault that defines the east side of the Emerson Pass valley. A maximum temperature of 35°C was recorded near several large tufa mounds on the valley floor down-gradient from a NNW-striking, west dipping normal fault. Also indicated on GTP ARRA spreadsheet, 3/24/2011"
    icated on GTP ARRA spreadsheet, 3/24/2011"  +
  • "A survey of diffuse CO2 efflux, soil temp
    "A survey of diffuse CO2 efflux, soil temperature and soil-gas chemistry over areas of localized vegetation-kill on and around the resurgent dome of Long Valley caldera California was performed to evaluate the premise that gaseous and thermal anomalies are related to renewed intrusion of magma. Some kill sites are long-lived features and others have developed in the past few years. Total anomalous CO2 emissions from the thirteen areas average around 8.7 t per day; but the majority of the emissions come from four sites west of the Casa Diablo geothermal power plant. Geochemical analyses of the soil-gases from locations west and east of the plant revealed the presence of isobutane related to plant operations. The Δ13C values of diffuse CO2 range from - 5.7‰ to - 3.4‰, similar to values previously reported for CO2 from hot springs and thermal wells around Long Valley. At many of the vegetation-kill sites soil temperatures reach boiling at depths <= 20 cm. Soil temperature/depth profiles at two of the high-emissions areas indicate that the conductive thermal gradient in the center of the areas is around 320°C m- 1. We estimate total heat loss from the two areas to be about 6.1 and 2.3 MW. Given current thinking on the rate of hydrothermal fluid flow across the caldera and using the CO2 concentration in the thermal fluids, the heat and CO2 loss from the kill areas is easily provided by the shallow hydrothermal system, which is sourced to the west of the resurgent dome. We find no evidence that the development of new areas of vegetation kill across the resurgent dome are related to new input of magma or magmatic fluids from beneath the resurgent dome. Our findings indicate that the areas have developed as a response to changes in the shallow hydrologic system. Some of the changes are likely related to fluid production at the power plant, but at distal sites the changes are more likely related to seismicity and uplift of the dome."
    ted to seismicity and uplift of the dome."  +
  • "An initial 2-meter survey was conducted a
    "An initial 2-meter survey was conducted at Teels Marsh in November and December of 2007. The range bounding Excelsior fault was followed as closely as terrain would allow. The two week effort resulted in over 80 measurements covering a distance greater than 26 km and the identification of two anomalous temperature zones (Figure 2). Temperatures in the northern anomaly reached as high as 26°C while temperatures at the southern anomaly were up to 35°C. These data stand in contrast to background temperatures of approximately 16-18°C. More recently, infill work completed in May 2008 provided detail at the southern anomaly. A deeper probe inserted at the location of the highest measured 2-meter-deep temperature reached a temperature of 65°C (148°F) at a depth of 9.5 meters (31 feet, Figure 3). The two anomalous temperature zones at Teels Marsh have a combined strike length of almost 4 km parallel to the western end of the Excelsior Mountain fault, and both occur where the strike of the fault changes from northeast to northwest."
    ault changes from northeast to northwest."  +
  • "CO2 and heat fluxes were measured over a
    "CO2 and heat fluxes were measured over a six-week period (09/08/2006 to 10/24/2006) by the eddy covariance (EC) technique at the Horseshoe Lake tree kill (HLTK), Mammoth Mountain, CA, a site with complex terrain and high, spatially heterogeneous CO2 emission rates. EC CO2 fluxes ranged from 218 to 3500 g m- 2 d- 1 (mean = 1346 g m- 2 d- 1). Using footprint modeling, EC CO2 fluxes were compared to CO2 fluxes measured by the chamber method on a grid repeatedly over a 10-day period. Half-hour EC CO2 fluxes were moderately correlated (R2 = 0.42) with chamber fluxes, whereas average daily EC CO2 fluxes were well correlated (R2 = 0.70) with chamber measurements. Average daily EC CO2 fluxes were correlated with both average daily wind speed and atmospheric pressure; relationships were similar to those observed between chamber CO2 fluxes and the atmospheric parameters over a comparable time period. Energy balance closure was assessed by statistical regression of EC energy fluxes (sensible and latent heat) against available energy (net radiation, less soil heat flux). While incomplete (R2 = 0.77 for 1:1 line), the degree of energy balance closure fell within the range observed in many investigations conducted in contrasting ecosystems and climates. Results indicate that despite complexities presented by the HLTK, EC can be reliably used to monitor background variations in volcanic CO2 fluxes associated with meteorological forcing, and presumably changes related to deeply derived processes such as volcanic activity."
    ived processes such as volcanic activity."  +
  • "Conceptual Model: Based on conceptual mo
    "Conceptual Model: Based on conceptual models built primarily from MT and geochemical datasets, it appears that development of the Akutan geothermal resource for power and/or direct use may be feasible. These datasets point to a shallow, tabular aquifer(s) of 155-180degrees C (i.e., "outflow zone") and a deeper, hotter resource of >220degrees C (i.e., "upflow zone") that will be targeted because of its potentially lower development cost. The initial exploratory wells will attempt to verify the existence of these aquifers, and determine their potential for development. "
    termine their potential for development. "  +
  • "DC electrical sounding measurements provi
    "DC electrical sounding measurements provide a 2-D image of the resistivity distribution beneath Long Valley Caldera. Conductive zones and SP anomalies correlate with the location of known faults in agreement with previous electrical surveys of this area. The resistivity structure in the western part of the caldera with two prominent high conductive features reflects a present-day shallow hydrothermal system that is also observed in temperature logs (Sorey et al., 1991). We conclude that the part of the resurgent dome to a depth of 2.0^2.5 km is not part of the shallow hydrothermal system identified to the west. The deeper conductive regions here may be caused by hydrothermal alteration or a fluid filled fracture system."
    ration or a fluid filled fracture system."  +
  • "Data collected since 1985 from test drill
    "Data collected since 1985 from test drilling, fluid sampling, and geologic and geophysical investigations provide a clearer definition of the hydrothermal system in Long Valley caldera than was previously available. This information confirms the existence of high-temperature (> 200°C) reservoirs within the volcanic fill in parts of the west moat. These reservoirs contain fluids which are chemically similar to thermal fluids encountered in the central and eastern parts of the caldera. The roots of the present-day hydrothermal system (the source reservoir, principal zones of upflow, and the magmatic heat source) most likely occur within metamorphic basement rocks beneath the western part of the caldera. Geothermometer-temperature estimates for the source reservoir range from 214 to 248°C. Zones of upflow of hot water could exist beneath the plateau of moat rhyolite located west of the resurgent dome or beneath Mammoth Mountain. Lateral flow of thermal water away from such upflow zones through reservoirs in the Bishop Tuff and early rhyolite accounts for temperature reversals encountered in most existing wells. Dating of hot-spring deposits from active and inactive thermal areas confirms previous interpretations of the evolution of hydrothermal activity that suggest two periods of extensive hot-spring discharge, one peaking about 300 ka and another extending from about 40 ka to the present. The onset of hydrothermal activity around 40 ka coincides with the initiation of rhyolitic volcanism along the Mono-Inyo Craters volcanic chain that extends beneath the caldera's west moat."
    extends beneath the caldera's west moat."  +
  • "Detailed XRD studies of alteration minera
    "Detailed XRD studies of alteration mineralogy in west-moat drill holes (Flexser, 1989, 1991-this volume) show that the present temperatures in RDO-8, PLV-1, and INYO-4 are well below (65°C or more) alteration temperatures, except in the lower part of RDO-8 (below about 300 m). No XRD evidence of epidote or other relatively high-temperature ( > 230°C) alteration products was found in any of the core."
    on products was found in any of the core."  +
  • "Detailed chemical and isotopic studies no
    "Detailed chemical and isotopic studies not only help quantify the discharge, but also may provide additional insight to subsurface conditions. For example, CO2-rich groundwaters that are cold and dilute may be a general indicator that a volcano contains a pressurized gas cap."
    a volcano contains a pressurized gas cap."  +
  • "EM sounding, MT, CSAMT, dipole-dipole resistivity; reservoir model?"  +
  • "Four wells have been successfully drilled
    "Four wells have been successfully drilled into this resource since the early 1980s using a combination of funds provided by the California Energy Commission (CEC) and the United State Department of Energy (USDOE). The first three wells, FB-1, -2 and -3 have been discussed in a previous paper (Barker et al., 2005). The current status of the FBIC project to evaluate the potential geothermal resource under the reservation is that a deep exploration test well has been successfully drilled and that so far there is no data that invalidates the proposed geologic model with a hypothesized upflow temperature of 250-300 degreesF (121-149 degrees C). Thus, the proposed "play" concept is still valid and confirmation awaits obtaining of additional funds. An estimate of the funds needed has been made by Atkinson and Vass (2010, pp 15-17) - approximately $1,100,000 escalated to December 2011. In conclusion, the FBIC has succeeded in maintaining control of its geothermal assets and has a sound foundation from which to continue exploration when funding allows."
    continue exploration when funding allows."  +
  • "Growing interest and exploration dollars
    "Growing interest and exploration dollars within the geothermal sector have paved the way for increasingly sophisticated suites of geophysical and geochemical tools and methodologies. The efforts to characterize and assess known geothermal fields and find new, previously unknown resources has been aided by the advent of higher spatial resolution airborne geophysics (e.g. aeromagnetics), development of new seismic processing techniques, and the genesis of modern multi-dimensional fluid flow and structural modeling algorithms, just to name a few. One of the newest techniques on the scene, is hyperspectral imaging. Really an optical analytical geochemical tool, hyperspectral imagers (or imaging spectrometers as they are also called), are generally flown at medium to high altitudes aboard mid-sized aircraft and much in the same way more familiar geophysics are flown. The hyperspectral data records a continuous spatial record of the earth's surface, as well as measuring a continuous spectral record of reflected sunlight or emitted thermal radiation. This high fidelity, uninterrupted spatial and spectral record allows for accurate material distribution mapping and quantitative identification at the pixel to sub-pixel level. In volcanic/geothermal regions, this capability translates to synoptic, high spatial resolution, large-area mineral maps generated at time scales conducive to both the faster pace of the exploration and drilling managers, as well as to the slower pace of geologists and other researchers trying to understand the geothermal system over the long run."
    the geothermal system over the long run."  +
  • "Here we present a detailed thermal conduc
    "Here we present a detailed thermal conductivity profile for LVEW (Fig. 5a). Measurements were performed at the geothermal laboratory of the USGS on chips and core samples using divided bar and needle probe instruments. Detailed descriptions of these instruments and measurement procedures are given in Sass et al. (1971a,b)."
    dures are given in Sass et al. (1971a,b)."  +
  • "In order to provide a basis for improveme
    "In order to provide a basis for improvement of methods of geothermal resource estimation, we have grouped the diverse methods appearing in the literature into four categories: 1. Method of surface heat flux, 2. Volume methods, 3. Planar fracture method, 4. Methods of magmatic head budget. We shall describe each of these categories in turn, deferring evaluation of their respective advantages and limitations to the following section." "As already noted, none of the methods described in this report appears completely satisfactory. In fact, each method requires the knowledge of specific physical factors and geologic conditions, which knowledge is almost always lacking during the a priori evaluation of a given area prior to the establishment of a production history."
    he establishment of a production history."  +
  • "Localized Strain as a Discriminator of Hi
    "Localized Strain as a Discriminator of Hidden Geothermal Systems, Vasco and Foxall, 2005. Recent work has focused on (1) collaborating with Alessandro Ferretti to use Permanent Scatterer (PS) InSAR data to infer strain at depth, (2) working with Lane Johnson to develop a dynamic faulting model, and (3) acquiring InSAR data for the region surrounding the Dixie Valley fault zone in collaboration with Dr. William Foxall of LLNL. The InSAR data have been processed and an initial interpretation of the results is ongoing. In particular, we have InSAR stacks for over twenty pairs of scenes. The use of PS data and the development of data processing techniques, such as stacking, is critical for imaging slowly varying regional strains over many years. Dr. Ferretti has developed an effective processing technique to identify permanent scatterers and observe their motion with sub-centimeter accuracy. (4) Studying the role that faults play in controlling flow in hydrothermal/magmatic systems I have completed a study of fault-fluid interaction at the Yellowstone caldera. I have also been working on leveling, GPS, EDM, and gravity data from Long Valley, California. The inversion of the deformation data has allowed us to show those faults which appear to be controlling flow at depth."
    h appear to be controlling flow at depth."  +
  • "MT, EM sounding, SP?; SP data and reservoir model may be proprietary"  +
  • "Most of 26 small (0.4<~M<~3.1) micr
    "Most of 26 small (0.4<~M<~3.1) microearthquakes at Long Valley caldera in mid-1997, analyzed using data from a dense temporary network of 69 digital three-component seismometers, have significantly non-double-couple focal mechanisms, inconsistent with simple shear faulting. We determined their mechanisms by inverting P- and S-wave polarities and amplitude ratios using linear-programming methods, and tracing rays through a three-dimensional Earth model derived using tomography. More than 80% of the mechanisms have positive (volume increase) isotropic components and most have compensated linear-vector dipole components with outward-directed major dipoles. The simplest interpretation of these mechanisms is combined shear and extensional faulting with a volume-compensating process, such as rapid flow of water, steam, or CO2 into opening tensile cracks. Source orientations of earthquakes in the south moat suggest extensional faulting on ESE-striking subvertical planes, an orientation consistent with planes defined by earthquake hypocenters. The focal mechanisms show that clearly defined hypocentral planes in different locations result from different source processes. One such plane in the eastern south moat is consistent with extensional faulting, while one near Casa Diablo Hot Springs reflects en echelon right-lateral shear faulting. Source orientations at Mammoth Mountain vary systematically with location, indicating that the volcano influences the local stress field. Events in a 'spasmodic burst' at Mammoth Mountain have practically identical mechanisms that indicate nearly pure compensated tensile failure and high fluid mobility. Five earthquakes had mechanisms involving small volume decreases, but these may not be significant. No mechanisms have volumetric moment fractions larger than that of a force dipole, but the reason for this fact is unknown."
    but the reason for this fact is unknown."  +
  • "Our preferred model for the unusual event
    "Our preferred model for the unusual events is that of multiple ordinary earthquakes being triggered or forced by a fluid injection into a thin volcanic conduit. An example of such a structure would be a dike connected to one or more shear or wing fractures. In this model, resonant increases in pressure in the conduit would cause the shear fractures to fail seismically at fixed time delays. For the time delays seen at Long Valley, the dimensions of the conduits would be on the order of 24�74 m. Existing models of such a conduit's resonances show that they are highly damped (e.g. Ferrick et al., 1982), and thereby likely to produce only a few shear failures. We speculate that, with continued action of the triggering process, the sub-events could evolve into observable volcanic tremors at Long Valley."
    servable volcanic tremors at Long Valley."  +
  • "Recent drilling and sampling of hydrother
    "Recent drilling and sampling of hydrothermal fluids from Long Valley permit an accurate characterization of chemical concentrations and equilibrium conditions in the hydrothermal reservoir. Hydrothermal fluids are thermodynamically saturated with secondary quartz, calcite, and pyrite but are in disequilibrium with respect to aqueous sulfide-sulfate speciation. Hydrothermal fluids are enriched in 18O by approximately 1‰ relative to recharge waters. 18O and Cl concentrations in well cuttings and core from high-temperature zones of the reservoir are extensively depleted relative to fresh rhyolitic tuff compositions. Approximately 80% of the Li and 50% of the B are retained in the altered reservoir rock. Cl mass balance and open-system 18O fractionation models produce similar water-rock ratios of between 1.0 and 2.5 kg kg_1. These water-rock ratios coupled with estimates of reservoir porosity and density produce a minimum fluid residence time of 1.3 ka. The low fluid Cl concentrations in Long Valley correlate with corresponding low rock concentrations. Mass balance calculations indicate that leaching of these reservoir rocks accounts for Cl losses during hydrothermal activity over the last 40 ka."
    ydrothermal activity over the last 40 ka."  +
  • "SP, MT, dipole-dipole resistivity, CSAMT; sufficient electrical data may be available"  +
  • "SP, dipole-dipole resistivity, CSAMT; sufficient electrical data are available. Reservoir model?"  +
  • "Sample for the present investigation cons
    "Sample for the present investigation consist of drill core and cuttings from all lithologic units identified in LVEW, cuttings from volcanic rocks in LV 13-21, core samples of Early Rhyolite and Bishop Tuff from LV13-26 and core samples of Bishop Tuff from SF38-32, LV48-29 and LV66-28 (Figs. 1 and 2). Surface samples of Early Rhyolite, Bishop Tuff and Paleozoic metasediments (Fig. 1) were also selected for comparative analysis and processed by the same procedures as the well samples. This oxygen isotope and fluid inclusion study has allowed us to determine the pathways of fluid circulation, set limits on the thermal regime, and link the source of the heat to prolonged volcanic activity."
    the heat to prolonged volcanic activity."  +
  • "Shallow temperature gradient drilling beg
    "Shallow temperature gradient drilling began at the CMAGR in January of 2010. 13 temperature gradient holes were completed to a depth of 500' below ground surface. Sites were selected based on the compilation of previous exploration and resulting data is being integrated into the most recent geologic model. This model will form the basis for the selection of a deeper (2000'-4000') temperature gradient drilling campaign at the CMAGR in 2011."
    t drilling campaign at the CMAGR in 2011."  +
  • "Since 1978, volcanic unrest in the form o
    "Since 1978, volcanic unrest in the form of earthquakes and ground deformation has persisted in the Long Valley caldera and adjacent parts of the Sierra Nevada. The papers in this special volume focus on periods of accelerated seismicity and deformation in 1980, 1983, 1989-1990, and 1997-1998 to delineate relations between geologic, tectonic, and hydrologic processes. The results distinguish between earthquake sequences that result from relaxation of existing stress accumulation through brittle failure and those in which brittle failure is driven by active intrusion. They also indicate that in addition to a relatively shallow (7-10-km) source beneath the resurgent dome, there exists a deeper (~15-km) source beneath the south moat. Analysis of microgravimety and deformation data indicates that the composition of the shallower source may involve a combination of silicic magma and hydrothermal fluid. Pressure and temperature fluctuations in wells have accompanied periods of crustal unrest, and additional pressure and temperature changes accompanying ongoing geothermal power production have resulted in land subsidence. The completion in 1998 of a 3000-m-deep drill hole on the resurgent dome has provided useful information on present and past periods of circulation of water at temperatures of 100-200°C within the crystalline basement rocks that underlie the post-caldera volcanics. The well is now being converted to a permanent geophysical monitoring station."
    permanent geophysical monitoring station."  +
  • "Sufficient geophysical data are not available. Reservoir model?"  +
  • "The 2009 MT survey detects a resistivity
    "The 2009 MT survey detects a resistivity pattern typical of most economically viable geothermal reservoirs where a low resistivity, low permeability hydrothermal smectite alteration layer caps a higher temperature, permeable geothermal reservoir. The MT resistivity pattern indicates that a hydrothermally altered clay cap exists near the fumarole and probably overlies an outflow connection from the fumarole to the highest temperature hot springs."
    e to the highest temperature hot springs."  +
  • "The 87Sr/86Sr values of thermal waters an
    "The 87Sr/86Sr values of thermal waters and hydrothermal calcites of the Long Valley caldera geothermal system are more radiogenic than those of young intracaldera volcanic rocks. Five thermal waters display 87Sr/86Sr of 0.7081-0.7078 but show systematically lighter values from west to east in the direction of lateral flow. We believe the decrease in ratio from west to east signifies increased interaction of deeply circulating thermal water with relatively fresh volcanic rocks filling the caldera depression. All types of pre-, syn-, and post-caldera volcanic rocks in the west and central caldera have (87Sr/86Sr)m between about 0.7060 and 0.7072 and values for Sierra Nevada granodiorites adjacent to the caldera are similar. Sierran pre-intrusive metavolcanic and metasedimentary rocks can have considerably higher Sr-isotope ratios (0.7061-0.7246 and 0.7090-0.7250, respectively). Hydrothermally altered volcanic rocks inside the caldera have (87Sr/86Sr)m slightly heavier than their fresh volcanic equivalents and hydrothermal calcites (0.7068-0.7105) occupy a midrange of values between the volcanic/plutonic rocks and the Sierran metamorphic rocks. These data indicate that the Long Valley geothermal reservoir is first equilibrated in a basement complex that contains at least some metasedimentary rocks. Reequilibration of Sr-isotope ratios to lower values occurs in thermal waters as convecting geothermal fluids flow through the isotopically lighter volcanic rocks of the caldera fill."
    ghter volcanic rocks of the caldera fill."  +
  • "The Airborne Visible/Infrared Imaging Spe
    "The Airborne Visible/Infrared Imaging Spectrometer (AVIRIS) instrument acquired hyperspectral data over northern Fish Lake Valley in March 2003. The AVIRIS sensor is maintained by the Jet Propulsion Laboratory and collects data in 224 wavelengths from the visible to shortwave infrared (0.4 to 2.5 micro-m) at 2 m spatial resolution. The data set covers the Fish Lake Valley prospect and the Silver Peak Range foothills, which are bounded by the Emigrant Peak fault zone. Past studies have successfully used remote sensing data to map hydrothermal alteration as minerals display characteristic spectral signatures. Remote sensing studies compliment traditional field mapping, often identifying alteration minerals that are not obvious in the field. Remote sensing is used to classify mineralogy across very large geographic areas, in this case, ~190 km2. The AVIRIS data were processed using statistical and subjective methods to identify hydrothermal alteration minerals including opal, kaolinite, montmorillonite, muscovite, clinochlore, hematite, calcite and borates. Mineral distribution was compared to existing geologic maps, including a surficial geology map by Reheis and Block (2007). We identify previously unmapped deposits of siliceous sinter and several locations with abundant hydrothermal clays that appear to be fault-controlled."
    clays that appear to be fault-controlled."  +
  • "The gravity data are described by (Blackw
    "The gravity data are described by (Blackwell et al., 1999; 2002). On a basin-wide scale the gravity low in Dixie Valley is strongly asymmetrical from east to west. The west side is relatively well-defined by rapid horizontal changes in the gravity anomaly value, whereas along the east side horizontal changes are more subdued and often consist of several steps. The horizontal gradient of the gravity field has proved most useful in identifying the surface projection of subsurface contacts of greatest density contrast, (Blackwell et al., 2002). Thus where the contact is sharp and large the gravity gradient shows a high value, but in areas with shallow features or small density contrasts, the gravity gradient high represents the midpoint over that feature. The terrain slope is the slope of the contours in the direction of steepest descent so it locates the magnitude and direction of the steepest gradient in any area of the map. The gravity gradients have been used to constrain the positions of faults cutting the piedmont block. Modeling of the gravity data (Blackwell et al., 1999; 2002) shows that along much of the steep east side of the Stillwater Range, piedmont faults in the valley, not the fault defined by the topography accommodate most of the displacement between the range front and the valley bottom. The pattern of the residual gravity and the gravity gradients along the eastern side of the basin is complex and in general not parallel to the edge of the valley. In that area the presence of the dense Jurassic Humboldt mafic complex complicates the pattern and combined magnetic and gravity interpretation is needed to analyze the structure. Details of the analysis will be described in Blackwell et al. (2010)."
    be described in Blackwell et al. (2010)."  +
  • "The melt zones of volcanic clusters was analyzed with recent geological and geophysical data for five magma-hydrothermal systems were studied for the purpose of developing estimates for the depth, volume and location of magma beneath each area."  +
  • "This oxygen isotope and fluid inclusion study has allowed us to determine the pathways of fluid circulation, set limits on the thermal regime, and link the source of the heat to prolonged volcanic activity."  +
  • "This paper presents a plan for increasing
    "This paper presents a plan for increasing the mapped resource base for geothermal exploration in the Western US. We plan to image large areas in the western US with recently developed high resolution hyperspectral geobotanical remote sensing tools. The proposed imaging systems have the ability to map visible faults, surface effluents, historical signatures, and discover subtle hidden faults and hidden thermal systems. Large regions can be imaged at reasonable costs. The technique of geobotanical remote sensing for geothermal signatures is based on recent successes in mapping faults and effluents the Long Valley Caldera and Mammoth Mountain in California."
    ldera and Mammoth Mountain in California."  +
  • "This second paper provides more detailed
    "This second paper provides more detailed documentation on water and rock geochemistries and describes diagnostic major and trace element ratios and concentrations that can be used to distinguish tufa columns formed from thermal waters from those that formed from non-thermal waters." "In addition to providing a potentially diagnostic lithogeochemical tool for geothermal exploration, the analysis of lithium and other elements in tufa deposits could serve as exploration guides for hot spring lithium deposits."
    n guides for hot spring lithium deposits."  +
  • "To test if it would have been possible to
    "To test if it would have been possible to find the Tungsten Mountain geothermal system with a shallow temperature survey, more than 80 2-meter-deep temperatures were recorded during a two week period in late June and early July, 2007. These measurements spanned an 8-km-long zone parallel to the range front and extended eastward from the range front up to 2 km towards the playa's edge (Figure 1). Two-meter temperatures ranged from 14.0°C up to a maximum of 26.7° C. The higher temperatures correspond to the area of exploration drilling, although anomalously high temperatures extend northeastward beyond the area of drilling. These results help to better define a thermal anomaly that generally parallels the range-front for over 5 km and remains open to the northeast."
    r 5 km and remains open to the northeast."  +
  • "We investigate the effects of viscoelasti
    "We investigate the effects of viscoelastic (VE) rheologies surrounding a vertically dipping prolate spheroid source during an active period of time-dependent deformation between 1995 and 2000 at Long Valley caldera. We model a rapid magmatic inflation episode and slip across the South Moat fault (SMF) in late 1997. We extend the spherical VE shell model of Newman et al. (Newman, A.V., Dixon, T.H., Ofoegbu, G., Dixon, J.E., 2001. Geodetic and seismic constraints on recent activity at Long Valley caldera, California: Evidence for viscoelastic rheology. J. Volcanol. Geotherm. Res. 105, 183-206.) to include a prolate spheroid geometry more accurately representing the probable source geometry inferred from other studies. This paper presents the first attempt to geodetically constrain the volcanic deformation source volume at Long Valley, a parameter for hazard assessment. Including fault slip along the SMF explains significant deformation observed with several EDM baselines and components of two continuous GPS time series. Additionally, the model explains the spatial extent of deformation observed by InSAR data covering the 1997-98 inflation episode. For the time period studied, the VE model requires modest pressure changes (maximum of 14.3 MPa) that are far lower than the overburden pressure (~115 MPa), and less than the maximum for a purely elastic model with the same geometry and elastic strength (~45 MPa). Thus, the inclusion of a realistic VE component significantly lowers the inferred pressures necessary to explain observed surface deformation. Though our model is non-unique, it is consistent with a broader variety of data compared to purely elastic models. Only right-lateral slip, and not dilitation, was necessary to explain offsets in EDM data near and crossing the SMF."
    ts in EDM data near and crossing the SMF."  +
  • "active seismic" - assume reflection  +
  • "active seismic" - did not specify reflection or refraction  +
  • "active seismic" - no indication as to whether reflection or refraction  +
  • "active seismic" - no indication of reflection or refraction  +
  • "active seismic" - no info on whether reflection or refraction  +
  • "geothermometry" - no indication of silica or cation  +
  • "seismic analyses" - no indication of acti
    "seismic analyses" - no indication of active/passive, reflection/refraction, etc. ---> "On the contrary, in areas with little or no volcanic activity, assumptions on the nature, size and characteristics of the source of the thermal anomaly are generally much more difficult and hypothetical. In these circumstances, some useful data can be obtained from accurate seismic analyses, together with a seismotectonic and geodynamic interpretation of all the available information such as historic seismic events, deep velocity of seismic waves, etc. Reasonable hypotheses can usually be formulated for the presence of active regional phenomena favoring the development of a heat anomaly, such as a mantle rise, presence of shallow magma chambers, wide acidic intrusions, regional deep faulting, etc."
    intrusions, regional deep faulting, etc."  +
  • "shallow temp"  +
  • "sufficient geophysical data are not available"  +
  • (1) Assembly and review of relevant published and proprietary literature and previous geothermal investigations in the region;  +
  • (2) detailed geologic mapping of the Emigrant Miocene sedimentary basin and surrounding Paleozoic basement rocks;  +
  • (4) synthesis of geologic mapping results
    (4) synthesis of geologic mapping results and lithologic logs for 3_D geologic characterization of the prospect area; (5) compilation of relevant data from the foregoing sub_activities into a Geographic Information Systems (GIS) database for visualization and mapping, and to facilitate the development of an exploration model; and (6) development of a refined conceptual geologic model to guide siting of the proposed slim hole.
    to guide siting of the proposed slim hole.  +
  • (Louisiana & Mississippi): "cased, non
    (Louisiana & Mississippi): "cased, non-flowing boreholes at least 150 m deep were sought on an opportunistic basis through state geological surveys and U.S. Geological Survey offices. Representative samples of drill cuttings were used for laboratory measurements of thermal conductivity. A total of 38 new heat flow values, ranging from less than 1 heat flow unit (hfu) (41.8 mW/m 2) to more than 2 hfu, were determined (Smith and Dees, in preparation), and a wedge-shaped zone of elevated thermal gradients and positive heat flow anomalies can be depicted (Fig. 1)."
    flow anomalies can be depicted (Fig. 1)."  +
  • (maybe)  +