Development of new marine TDEM systems for the ocean bottom hydrothermal deposits

Widely accepted Time Domain EM technologies for the onshore mineral explorations are applied to the ocean bottom mineral deposits, by developing new systems with ROV (remotely operated vehicle) and practical test surveys were conducted at Ogasawara and Okinawa areas. The first parts of these developments were already published by Nakayama et al. (2011), including 3D numerical simulation and analog water tank modeling. The two new measuring systems of moving and fixed types were introduced in 2012 and the test surveys were conducted and the developed systems are proved to be practical for the marine survey. We have made the measurements of the chemical and physical properties of the ocean bottom mineral ores samples, and some of the seabed sulfide ores showed higher IP effects than the onshore samples called Black Ore which is the same ocean bed hydrothermal origin (Shingyoji et al. 2009). Then we developed new inductive square array method to measure IP effects using TDEM transmitting coil as the eddy current source.