HR: 1340h
AN: T23B-0554    [Abstracts]
TI: Geophysical Investigations to Assess Geothermal Energy Potential, Socorro Peak, New Mexico
AU: * Tobin, H J
EM: tobin@nmt.edu
AF: New Mexico Tech, Earth and Env. Science Dept., Socorro, NM 87801 United States
AU: Baars, R M
EM: rmbaars@nmt.edu
AF: New Mexico Tech, Earth and Env. Science Dept., Socorro, NM 87801 United States
AU: Norman, D
EM: dnorman@nmt.edu
AF: New Mexico Tech, Earth and Env. Science Dept., Socorro, NM 87801 United States
AU: Owens, L
EM: lara@nmt.edu
AF: New Mexico Tech, Earth and Env. Science Dept., Socorro, NM 87801 United States
AU: Cumming, W
EM: wcumming@wcumming.com
AF: Cumming Geoscience, 4728 Shade Tree Lane, Santa Rosa, CA 95405 United States
AB: The Socorro Peak uplift in central New Mexico has long been known to host a strongly localized heat flow anomaly. Shallow thermal gradient wells show heat flows as high as 490 mW/m² at depths to ~100 m, superimposed on background values of 60-80 mW/m². Warm springs at the south end of the mountain block produce water of ~ 35 C, and show chemical evidence of thermal water highly diluted by shallow groundwater. Recently, interest has grown in assessing the potential for direct use of these thermal waters for space heating of buildings on the New Mexico Institute of Mining and Technology campus. We have therefore undertaken multidisciplinary exploration efforts in order to better understand the structure and hydrogeology of the hydrothermal system, and to site a planned 1000 m exploratory well. In particular, we have collected high-resolution magnetotelluric profile data at 100 m station spacing to characterize the near surface distribution of conductivity across the range bounding fault on the east side of the Socorro Peak uplift, where the geothermal gradients are highest. Two dimensional inversions of the data, constrained by known local geology, show that a single fault, corresponding to the mapped main fault, is the locus of major displacement for at least the upper 1000 m, juxtaposing footwall preCambrian and Paleozoic rocks and Tertiary volcaniclastics against hanging wall alluvial sediments of the Rio Grande Rift. We tentatively identify an imaged conductive zone at depths of 400 m or more below surface east of the fault as a regional aquitard separating the shallow groundwater from underlying possible hydrothermal systems, structurally juxtaposed with a moderately resistive block in the footwall. A synthesis of geophysical and geologic evidence for the architecture of this hydrothermal system places these units in fault contact at a strongly fractured intersection of the Socorro Canyon fault with the older ring fracture of the Socorro caldera, accompanied by localized leakage of the hydrothermal fluids in the footwall block into the rift sediment system.
DE: 5109 Magnetic and electrical properties (0925)
DE: 8010 Fractures and faults
DE: 8135 Hydrothermal systems (0450, 1034, 3017, 3616, 4832, 8424)
SC: Tectonophysics [T]
MN: Fall Meeting 2005