Division of Exploration Technology / Research and investigation committee on resource exploration from land to ocean to develop fundamental and big data processing techniques

[3101-06-05] Integration of spatial models of resistivity and chemical concentration data by drillings for metal-grade imaging of a seafloor hydrothermal vent area

○Vitor Ribeiro de Sá¹, Katsuaki Koike¹, Tadanori Goto¹, Katsuhiko Suzuki² (1. Kyoto University, 2. JAMSTEC)

Chairman: Akihisa Kizaki (Akita university)

Keywords:Geostatistics, Seafloor hydrothermal vent area, Resistivity-logging data, Element concentration, Okinawa Trough

Seafloor hydrothermal vent areas have been important exploration target as a source of volcanogenic massive sulphide (VMS) type deposit. As compared to land areas, geological information usually obtained by drilling surveys and well logging is quite limited in seafloor in both the amount and location. Therefore, spatial modeling of metal grade is difficult to be archived with adequate accuracy. For this problem, this study aims to enable such modeling by geostatistical analyses of resistivity and chemical concentration data by drillings in a seafloor hydrothermal vent area by selecting the Iheya North Knoll, situated 15 km NW of Okinawa Island, as a case study. This area is in the middle Okinawa Trough, a back-arc basin under an extensional stress field. Turning band, a geostatistical simulation method, is used to clarify the 3D resistivity distribution and then, the distribution is combined with the metal concentrations for producing a preliminary metal-grade model. As the result, high grade zones of layered shape are estimated at certain depths and their formation is considered to be controlled by hydrothermal fluid flows and mixing with sea water.