Observation and confirmation based on survey protocol for seafloor massive sulfide deposits using acoustic survey technique and self-potential surveys

Abstract

“Zipangu in the Ocean program,” a Strategic Innovation Promotion Program (SIP) managed by the cabinet office of the government of Japan, was launched for the scientific and technological development of natural resources around the Japan Islands for recent national requirements for marine natural resources. Under this project, “Protocol for the natural hydrothermal resources” was formulated, and we tried to confirm a part of this protocol on a research cruise. In the candidate areas we chose before the cruise, we obtained the bathymetry, back scatter, water column data by the dense surveys used MBES system on a ship and narrow the candidates for AUV surveys. A clear negative self-potential (SP) zone and many mound structures were detected by AUV surveys using an electrometer and a high accuracy MBES system on an AUV in the one area of five candidates for detailed surveys. Many detailed distributions of hydrothermal plumes were also found. However, our survey methods enabled effective data acquisition for hydrothermal deposits exploration. According to the survey results in the known hydrothermal deposit, the negative SP anomaly relates to the hydrothermal deposit on the seafloor and/or under the seafloor. Therefore, this result implies that the SP anomaly detects the sub-surface structures. It is needed to obtain the certain direct evidence with hydro-thermal deposit and the detailed electrical structural analysis to confirm the reliability of our survey results. However, our survey methods obtained effective data acquisition under the hydrothermal deposit survey. New knowledges of this observation are very important guideline for the unknown hydrothermal deposit survey.