HR: 14:55h
AN: V53F-06    [Abstracts]
TI: Development of Genetic Occurrence Models for Geothermal Prospecting
AU: * Walker, J D
EM: jdwalker@ku.edu
AF: Department of Geology, University of Kansas, Lawrence, KS 66045, United States
AU: Sabin, A
EM: asabin@itsi.com
AF: Innovative Technical Solutions, Inc., 2730 Shadelands Dr., Suite 100, Walnut Creek, CA 94598, United States
AU: Unruh, J
EM: unruh@lettis.com
AF: William Lettis and Associates, 1777 Bothelo Drive, Walnut Creek, CA 94596, United States
AU: Monastero, F C
AF: Geothermal Program Office (ESC-25), Naval Air Weapons Station 429 E. Bowen Road, Mail Stop 4011, China Lake, CA 93555, United States
AU: Combs, J
EM: jimjeany@ix.netcom.com
AF: Geo Hills Associates LLC, 2445 East Lakeridge Shores, Reno, NV 89509, United States
AB: Exploration for utility-grade geothermal resources has mostly relied on identifying obvious surface manifestations of possible geothermal activity, e.g., locating and working near steaming ground or hot springs. This approach has lead to the development of over 130 resources worldwide, but geothermal exploration done in this manner is akin to locating hydrocarbon plays by searching for oil seeps. Confining exploration to areas with such features will clearly not discover a blind resource, that is, one that does not have surface expression. Blind resources, however, constitute the vast majority of hydrocarbon plays; this may be the case for geothermal resources as well. We propose a geothermal exploration strategy for finding blind systems that is based on an understanding of the geologic processes that transfer heat from the mantle to the upper crust and foster the conditions for hydrothermal circulation or enhanced geothermal exploration. The strategy employs a genetically based screening protocol to assess potential geothermal sites. The approach starts at the plate boundary scale and progressively focuses in on the scale of a producing electrical-grade field. Any active margin or hot spot is a potential location for geothermal resources. Although Quaternary igneous activity provides a clear indication of active advection of hot material into the upper crust, it is not sufficient to guarantee a potential utility-grade resource. Active faulting and/or evidence of high strain rates appear to be the critical features associated with areas of utility-grade geothermal potential. This is because deformation on its own can advect sufficient heat into the upper crust to create conditions favorable for geothermal exploitation. In addition, active deformation is required to demonstrate that open pathways for circulation of geothermal fluids are present and/or can be maintained. The last step in the screening protocol is to identify any evidence of geothermal activity, including high heat flow, anomalous temperature water wells, high-temperature indications from aqueous geothermometry and geochemistry, Pliocene or younger ages from low-temperature thermochronometers, as well as more obvious factors such as geysers and fumaroles (which by definition will be missing for blind resources). Our occurrence-model strategy inverts the current approach that relies first on obvious evidence of geothermal activity. We evaluated our approach by retrospectively applying the protocol to the characteristics of producing geothermal fields, and in all cases, known resource areas fit the parameters identified from a genetic perspective.
DE: 8130 Heat generation and transport
DE: 8135 Hydrothermal systems (0450, 1034, 3017, 3616, 4832, 8424)
DE: 8424 Hydrothermal systems (0450, 1034, 3017, 3616, 4832, 8135)
SC: Volcanology, Geochemistry, Petrology [V]
MN: 2007 Fall Meeting