Natural gamma ray logging at sea-floor hydrothermal deposit in Izena Hole off-shore Okinawa

Yoshinori Sanada, Yasuhiro Yamada, Kazuya Kitada, Tatsuo Nozaki, Hidenori Kumagai, Jun Ichiro Ishibashi, Lena Maeda

Research output: Contribution to conferencePaperpeer-review

1 Citation (Scopus)


Natural gamma ray logging was carried out at the five wells in Izena Hole off-shore Okinawa by D/V Chikyu on November to December in 2016. This is one of the research cruise under an umbrella of Cross-ministerial Strategic Innovation Promotion Program (SIP), "Next-generation technology for ocean resources exploration (Zipangu in the Ocean program)". The purpose of this survey is to understand geological profile and distribution of the subsurface hydrothermal deposit. It is difficult to take good quality and recovery cores in hydrothermal brittle formation. On the other hand, the continuous natural gamma ray logging data allows us to describe continuous vertical formation profile. The memory-type logging tool was stuck out just below the drill bit at the bottom of borehole after cutting cores. The tool measures logging data during pulling out of the hole. Natural gamma ray, temperature and pressure were measured in the boreholes. The gamma ray data by logging tool has good correlation with that in the core data by laboratory measurement until ~30-80m below sea floor at the good core recovery intervals. The logging data are only continuous profile below the depth till maximum 180m below sea floor. The gamma ray data indicate classification of sediment layer, ore body, and alternate layer in this region. The temperature logging indicates potential of hydrothermal deposit activity. The pressure data shows static water column.

Original languageEnglish
Publication statusPublished - 2017
Event23rd Formation Evaluation Symposium of Japan 2017 - Chiba, Japan
Duration: Oct 11 2017Oct 12 2017


Other23rd Formation Evaluation Symposium of Japan 2017

All Science Journal Classification (ASJC) codes

  • Geotechnical Engineering and Engineering Geology
  • Geology
  • Energy Engineering and Power Technology
  • Economic Geology
  • Geochemistry and Petrology


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