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The Development of Time Domain Ocean Bottom EM System Capable of Measuring Magnetic, IP and SP Anomalies
- Publisher: European Association of Geoscientists & Engineers
- Source: Conference Proceedings, 3rd Applied Shallow Marine Geophysics Conference, Sep 2018, Volume 2018, p.1 - 5
Abstract
As a practical exploration method for seafloor hydrothermal mineral deposits, we developed a time-domain EM system towed with a ROV. We included a magneto- impedance (MI) seafloor magnetometer with high sensitivity and wide-band MI elements, and a three-component fluxgate seafloor magnetometer functioned as the receiving magnetic sensors. Furthermore, we used three pairs of electrodes, measuring three components of the electrical potential differences to measure SP (spontaneous electrical potential), and a coincident-type receiver loop for resistivity and IP (induced polarization) measurement. Around known deposits in the Okinawa area, conductive anomalies caused by hydrothermal mineral deposits were clearly observed, and we showed that the existence of these hydrothermal deposits below the seafloor can be measured by this method. The current investigated depth is 25–35 m from the seafloor. SP anomalies measured after the electromagnetic induction phenomenon was completed at each measurement point were present at the conductive anomaly captured by this electromagnetic method,showing downward current flow on the mineral body.