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Combining 3D ERT, drone and satellite images with geochemical analysis to investigate the nature of the Goshogake hydrothermal field, Japan.

Matteo Lupi 1, Adriano Mazzini2, Kareshma Narine1, Julien Sfalcin3, Marceau Gresse4, Perach Nuriel1

  • Affiliations: 1Department of Earth Sciences, University of Geneva, Geneva, Switzerland 2Department of Earth Sciences, University of Oslo, Oslo, Norway 3Invert, Echichens, Switzerland 4Geological Survey of Japan (AIST), Ibaraki, Japan

  • Presentation type: Talk

  • Presentation time: Thursday 11:00 - 11:15, Room R290

  • Programme No: 3.8.3

  • Theme 3 > Session 8

Abstract

The western flank of the Akita Yakeyama Volcano (Tokoku, Japan), hosts the Goshogake hydrothermal system. Interestingly, Goshogake lies between the magmatic volcanic arc and the sedimentary hydrocarbon-rich backarc of Japan. Goshogake features a large variety of surface manifestations with temperatures ranging from 33 to 97 °C along with acidic pH values of approximately 2.5. The hydrothermal emissions emerge at the base of a narrow valley, where a N-S fault system framing the Akita Yakeyama volcano is suggested to occur. We conducted a 3D Deep Electrical Resistivity Tomography, combined with drone-derived thermal photogrammetry and satellite images. A total of 25 Iris Fullwavers were deployed to acquire electrical resistivity data across the Goshogake hydrothermal field. The inverted resistivity model shows a conductive system enabling differentiation of the conduits feeding the vents. Data were compared with geochemical analyses which indicate that the active sites are H2S- and CO2-dominated with a clear mantle-derived isotopic signature. In contrast, colder seepage sites reveal the presence of minor quantities of methane, although its origin (either thermogenic or abiotic) remains unsolved. Ongoing analyses conducted on the inferred oil films will allow to distinguish its origin. Potential scenarios include a) the presence of shallow oil derived from the alteration of recent organic-rich deposits, or b) deep oil originating from the thermo-methamorphism of deep seated lacustrine deposits hosting the volcanic complex. If the second scenario is validated, Goshogake could well be Japan's first known example of a sedimentary-hosted geothermal system considerably increasing regions suited for geothermal potential.