Investigation of geothermal potential in the Waianae caldera area, Western Oahu, Hawaii

"Studies of Lualualei Valley, Oahu have been conducted to determine whether a thermal anomaly exists in the area and, if so, to identify sites at which subsurface techniques should be utilized to characterize the resource. Geologic mapping identifies several caldera and rift zone structures in the Valley and provides a tentative outline of their boundaries. Clay mineralogy studies indicate that minor geothermal alteration of near-surface rocks has occurred at some period in the history of the area. Schlumberger resistivity soundings indicate the presence of a low resistivity layer beneath the valley floor, which has been tentatively attributed to warm water-saturated basalt. Soil and groundwater chemistry studies outline several geochemical anomalies around the perimeter and within the inferred caldera boundaries. The observed anomalies strongly suggest a subsurface heat source. Recommendations for further exploratory work to confirm the presence of a geothermal reservoir include more intensive ·surveys in a few selected areas of the valley as well as the drilling of at least three shallow (1000-m) holes for subsurface geochemical, geological and geophysical studies.""Prepared for Western States Cooperative Direct Heat Resource Assessment."Contents: Geology of Oahu and Waianae Volcano / Malcolm E. Cox and Donald M. Thomas -- Detailed geological mapping / John M. Sinton -- Mineral assemblages of basalt and soil samples / Donald M. Helstern and Pow-foong Fan -- Summary of regional geophysics / Malcolm E. Cox -- Geoelectric surveys / Mark D. Mattice and James P. Kauahikaua -- Geochemical surveys / Malcolm E. Cox and Donald M. ThomasBibliography: pages 73-76.U.S. Department of Energy grant no. DOE/ID/01713-