Carbon-forming reactions under a reducing atmosphere during seismic fault slip

Abstract

Research Article| September 01, 2014 Carbon-forming reactions under a reducing atmosphere during seismic fault slip Kiyokazu Oohashi; Kiyokazu Oohashi * 1Department of Earth Sciences, Graduate School of Science, Chiba University, Chiba 263-8522, Japan *E-mail: oohashik@earth.s.chiba-u.ac.jp. Search for other works by this author on: GSW Google Scholar Raehee Han; Raehee Han 2Geologic Environment Division, Korea Institute of Geoscience and Mineral Resources (KIGAM), Daejeon 305-350, South Korea Search for other works by this author on: GSW Google Scholar Takehiro Hirose; Takehiro Hirose 3Kochi Institute for Core Sample Research, Japan Agency for Marine-Earth Science and Technology (JAMSTEC), Kochi 783-8502, Japan Search for other works by this author on: GSW Google Scholar Toshihiko Shimamoto; Toshihiko Shimamoto 4State Key Laboratory of Earthquake Dynamics, Institute of Geology, China Earthquake Administration, P.O. Box 9803, Beijing 100029, China Search for other works by this author on: GSW Google Scholar Kentaro Omura; Kentaro Omura 5National Research Institute for Earth Science and Disaster Prevention (NIED), Tsukuba 305-0006, Japan Search for other works by this author on: GSW Google Scholar Tatsuo Matsuda Tatsuo Matsuda 6Real-time Earthquake & Disaster Information Consortium, Shinjuku 160-0016, Japan Search for other works by this author on: GSW Google Scholar Geology (2014) 42 (9): 787–790. https://doi.org/10.1130/G35703.1 Article history received: 22 Mar 2014 rev-recd: 16 Jun 2014 accepted: 26 Jun 2014 first online: 09 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share MailTo Twitter LinkedIn Tools Icon Tools Get Permissions Search Site Citation Kiyokazu Oohashi, Raehee Han, Takehiro Hirose, Toshihiko Shimamoto, Kentaro Omura, Tatsuo Matsuda; Carbon-forming reactions under a reducing atmosphere during seismic fault slip. Geology 2014;; 42 (9): 787–790. doi: https://doi.org/10.1130/G35703.1 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGeology Search Advanced Search Abstract Graphite is a well-known solid lubricant and can be as important as clay minerals in reducing the frictional strength of faults. Some natural fault zones contain carbonaceous material (CM) even where host rocks do not contain it, and seismic fault motion can promote the graphitization of low-grade CM. Thus, the origin of CM in fault zones is an important issue in fault mechanics. Previous high-velocity friction experiments have revealed various chemical reactions in fault zones during seismic fault motion, but most experiments have been conducted in an atmosphere under oxic conditions. Here we report experimental results on Carrara marble (free of CM), conducted under N2 or H2 atmospheres at a slip rate of 1.3 m/s and normal stresses of 2.0–3.1 MPa. A small amount of blackish material formed in generated gouge only under reducing conditions with the H2 atmosphere, and Raman spectroscopic analysis revealed the presence of CM (amorphous carbon) in the material. The CM is attributable to (1) the generation and pyrolitic dissociation of CH4, and/or (2) a reduction reaction of emitted CO2 due to calcite decomposition. We confirmed the formation of CH4 using gas chromatography. The CM produced in experiments resembles CM in the Nojima fault (Japan) gouge in terms of Raman spectra. The granitic host rock of this fault is free of CM, and calcite is precipitated close to the CM; therefore, the CM probably formed through processes similar to those simulated in our experiments. Future research should investigate the amount and origin of CM in natural fault zones. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.