SEGJ Technical Conference

Electrical and Gravity Explorations off the west coast of Kumejima

Abstract The electrical prospecting methods were conducted by a deep-tow off the west of Kumejima where the existence of the hydrothermal ore deposit was partially known, and ocean bottom gravity survey was also conducted by a ROV. In the electric survey, clear SP anomalies were observed, and the results that the areas showing the negative SP anomaly were simultaneously lower resistivity than the seawater were obtained. Based on this result and the result of the seismic reflection survey, six bowling points were selected. Five of them were points where negative SP anomaly and low resistivity were shown, and one was close to these anomalies, but no anomaly was observed. As a result, in the previous five points, the sulfide layer was confirmed although there was some amount, and at the later point there was not found sulfide layer. The ocean bottom gravity survey was also conducted on two lines crossing these bowling points in the east-west direction. As a result, high gravity anomaly was observed around the point where the sulfide layer was the thickest, which indicates that the high density materials are buried. This is considered to indicate the scale of the sulfide deposit.