Geothermal

http://www.unr.edu/Geothermal/pdffiles/Faulds06StructuralNWGB.pdf

 www.unr.edu/Geothermal/pdffiles/Faulds06StructuralNWGB.pdf
Characterizing Structural Controls of Geothermal Fields  
in the Northwestern Great Basin: A Progress Report 

James E. Faulds, Garrett S. Vice, Melissa L. Edwards, Nevada Bureau of Mines and Geology, University of Nevada, Reno, NV 
Mark F. Coolbaugh, Great Basin Center for Geothermal Energy, University of Nevada, Reno, NV

Considering a lack of recent volcanism, the abundant geo- 
thermal activity in the northwestern Great Basin is somewhat 
anomalous.  The prolific activity may result from enhanced 
dilation on N- to NNE-striking normal faults induced by a 
transfer of NW-directed dextral shear from the Walker Lane 
to NW-directed extension in the Great Basin.  Although faults 
control most geothermal activity in the Great Basin, few 
detailed investigations have been conducted on the specific 
structural controls of individual fields.  Because knowledge of 
such structures would facilitate exploration models, we have 
embarked upon a regional study of the controls on geother- 
mal activity, which includes detailed analysis of several fields, 
reconnaissance studies of many other fields, and compilation 
of existing data.  Our findings from the Bradys, Desert Peak, 
Needle Rocks, Salt Wells, and Gerlach geothermal systems 
suggest that many fields occupy discrete steps in fault zones 
or lie in belts of intersecting, overlapping, and/or terminating 
faults.  In addition, most fields are associated with steeply dip- 
ping faults and, in many cases, with Quaternary faults.  The 
structural settings favoring geothermal activity all involve 
subvertical conduits of highly fractured rock along fault zones 
oriented approximately perpendicular to the least principal 
stress.  Features indicative of these settings that may be helpful 
in guiding exploration include: 1) major steps in range-fronts, 
2) interbasinal highs, 3) mountain ranges consisting of rela- 
tively low, discontinuous ridges, and 4) lateral terminations 
of mountain ranges.