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Sparks, NV, United States

Martini B.A.,Ormat Nevada Inc. | Lide C.,Zonge International | Owens L.,Ormat Nevada Inc. | Walsh P.,Ormat Nevada Inc. | And 2 more authors.
Transactions - Geothermal Resources Council | Year: 2011

The active, Aleutian-arc stratovolcano Mt. Spurr and its flank-cone, Crater Peak, are the target of current geothermal exploration in the western Cook Inlet. Lying just 80 miles west of Anchorage, AK, the Mt. Spurr complex serves as both a source of hazard and of potential energy. Recent eruptive episodes ('53 and '92) make development here challenging - but the young nature of the volcanic system (all less than ∼255ka), extensive, active faulting, advanced surface alteration suites and fluid chemistries consistent with a geothermal reservoir, also make Mt. Spurr very prospective. Field reconnaissance during the summer of 2009 (including mapping and surface geochemical sampling) set the stage for a full-scale exploration program in the summer of 2010. High resolution satellite imagery coupled with LiDAR kicked-off the exploration program, providing base maps (especially structure) of this poorly known edifice. Heli-bourne aeromagnetics and an aggressive ground-based geophysical suite of gravity and MT were completed over several months. The synthesis of these datasets with additional geologic mapping, geochemical sampling and two ∼1000′ core holes have produced a working geothermal exploration model and served to elucidate large scale structural controls on this young volcanic edifice. Both deep and shallow features were identified in the geophysics and airborne LiDAR, including large scale conductors coincident with surface hydrothermal fluid flow, de-magnetized regions coincident with LiDAR-delineated surface volcanic features and major and minor fault structures coincident with known regional structural trends. We plan to target these major structures (where coincident with geophysical anomalies) with additional intermediate depth core holes in the summer of 2011, the goal of which is to define a viable geothermal reservoir (temperature, fluid and permeability). Source

Beard L.P.,Zonge International
SEG Technical Program Expanded Abstracts | Year: 2011

Interpretation of out-of-loop data from fixed-loop transient EM surveys can be enhanced by using plate models. Numerical modeling shows it is possible to distinguish flatlying conductors from vertical conductive sheets by comparing the appearance of the vertical and along-line out of loop measurements. Where multiple, steeply-dipping conductive sheets exist, the sheet nearest the transmitter may diminish the responses of more distant sheets, but will usually not cause the more distant sheet to be undetectable. Screening increases with closeness of adjacent plates and with increasing conductance. If the screening effect is not taken into account, estimates of conductance, and by inference, ore tonnage, may be underestimated. © 2011 Society of Exploration Geophysicists. Source

Wynn J.,U.S. Geological Survey | Williamson M.,Williamson and Associates | Fleming J.,Zonge International
Sea Technology | Year: 2012

The US Geological Survey (USGS) has developed and patented an electrical geophysical technology called marine induced polarization (IP) to map placer heavy minerals on and below the seafloor. A cooperative research and development agreement with several private companies has been set up to exploit this placer-mineral and hydrocarbon-mapping technology, which can be useful for mapping wrecks and is promising for rapidly mapping buried unexploded ordnance. For a subseafloor minerals application, the USGS uses a single streamer with a single current transmitter dipole, followed by multiple receiver dipoles at increasing distances. This allows mapping of IP-reactive minerals at different depths using various receiver channels. The IP anomaly coincides closely with the bathymetric signature of the northern paleochannel, seen approximately in contoured ilmenite assays. A much larger IP anomaly lies south and east of this paleochannel, where one would expect the Agulhas Current along with longshore currents to have dispersed the ilmenite over time. Source

Calvin W.M.,University of Nevada, Reno | Littlefield E.F.,University of Nevada, Reno | Kratt C.,Zonge International
Geothermics | Year: 2015

We use remote sensing data from a variety of satellite and airborne instruments to characterize mineral and thermal properties as surface indicators of geothermal resources in Nevada. We generally use satellite data as a reconnaissance tool to target higher resolution airborne data collections. Spectral data are collected from field surface locations and samples to validate remote identifications and refine mineral maps. Spectral validation is done using an ASD portable spectrometer (0.4-2.5. μm) in both field and lab configurations. We also have a Thermo/Nicolet Nexus 6700 FTIR spectrometer and shared use of a Designs and Prototypes FTIR field instrument for thermal infrared data collection. Past work has identified sinter, tufa, travertine, argillic hydrothermal alteration minerals, evaporites, vegetation concentration near springs, and thermal anomalies as indicative of resource potential and structural controls on fluid pathways. Our methodology places mineral maps into GIS databases with other geologic information to make comparisons and site assessments. We recommend target areas for subsequent exploration including shallow temperature measurements, detailed geologic mapping, and structural analyses. This paper reviews over a decade of remote sensing geothermal exploration in Nevada and summarizes the common and unique features identified by our surveys. © 2014 Elsevier Ltd. All rights reserved. Source

Beard L.P.,Zonge International
Proceedings of the Symposium on the Application of Geophyics to Engineering and Environmental Problems, SAGEEP | Year: 2012

Hypervelocity meteor impacts create circular or oval craters and fracture the subsurface. This fracturing has been associated with geothermal resources, metallic ore deposits, and even oil and gas fields. These practical targets give the study of meteor impacts importance aside from the several more basic scientific reasons for impact crater research. An examination of the worldwide distribution of known impact crater locations shows that very few craters appear on or near the magnetic equator. Although this could be mere chance, it is possible that some low latitude impact craters are buried or hidden by heavy vegetation and are overlooked because their magnetic anomalies do not appear particularly ring-like. Magnetic anomalies from impacts are variable, but three main categories capture the majority: (1) simple ring anomalies created by the uplifted rim of the crater, (2) complex crater anomalies consisting of an outer ring and a center anomaly, and (3) a simple crater filled with nonmagnetic debris in modestly magnetic bedrock. At low magnetic latitudes, each of these types can produce induced magnetic anomalies with sufficient magnitudes for detection by aeromagnetic surveys, but which are not decidedly ring-like in appearance. Low latitude rings usually show sizeable anomalies only at their north, south, east, and west extremities. The east and west anomalies may not be large enough spatially to detect with wide line spacing, but the north and south anomalies are usually spatially broad. Most of the remainder of the ring is of such low magnitude as to be almost undetectable. Complex craters produce sizeable magnetic lows in the center. Craters filled with non-magnetic debris may produce detectable magnetic highs. The ability to predict what types of anomalies may be formed by low magnetic latitude impact craters may be useful in identifying these structures in areas such as West Africa or Brazil, where dense vegetation and poor access make detailed initial inspection problematic. Source

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