Electric-field-ratio Profiling at the Silsilah Tin-bearing Greisen Deposit, Kingdom of Saudi Arabia

Exploration & Mining Geology, Vol. 2, No. 2, 1993

ROBERT J. KAMILLI, U.S. Geological Survey, Tucson Field Office, University of Arizona, Tucson, Arizona, U.S.A., and CHARLES J. ZABLOCKI, U.S. Geological Survey, Saudi Arabian Mission, New York, U.S.A.

Buried, possibly mineralized granite cupolas at the Silsilah tin deposit in Saudi Arabia (lat. 26°06' N, long. 42°40' E) have been successfully located using a closely spaced electric-field-ratio profiling technique. In this study, electrical fields at 27 and 270 Hz across grounded electrodes spaced 50 m apart were measured along six traverses. This method is in-terpretable by inspection, unlike the dipole-dipole technique, which requires mathematical modeling for interpretation. In the study area, the technique allowed the authors to identify and distinguish among unroofed granite cupolas, cupolas with their aplite-pegmatite apical contact zones intact, strong (quartz-rich) and weak (relatively quartz-poor) greisens, dikes, faults, and pervasively argil-lized rocks. This method should be useful in the valuation of other shallow mineral prospects in similar settings in other parts of the world, especially deposits for which the location of vertical contrasts is important, such as veins or mineralized zones associated with the apexes of small igneous cupolas.