Carbonaceous materials in the fault zone of the longmenshan fault belt: 2. characterization of fault gouge from deep drilling and implications for fault maturity

Li Wei Kuo, Jyh Rou Huang, Jiann Neng Fang, Jialiang Si, Sheng Rong Song, Haibing Li, En Chao Yeh

研究成果: 雜誌貢獻文章

6 引文 斯高帕斯(Scopus)

摘要

In recent works on the determination of graphitization of carbonaceous materials (CM) within the principal slip zone (PSZ) of the Longmenshan fault (China), we demonstrated that the formation of graphite, resulted from strain and frictional heating, could be evidence of past seismic slip. Here we utilize Raman Spectroscopy of CM (RSCM) on the CM-bearing gouges in the fault zone of the Longmenshan fault belt, at the borehole depth of 760 m (FZ760) from the Wenchuan earthquake Fault Scientific Drilling project-1 (WFSD-1), to quantitatively characterize CM and further retrieve ancient fault deformation information in the active fault. RSCM shows that graphitization of CM is intense in the fault core with respect to the damage zone, with the graphitized carbon resembling those observed on experimentally formed graphite that was frictionally generated. Importantly, compared to the recognized active fault zone of the Longmenshan fault, the RSCM of measured CM-rich gouge shows a higher degree of graphitization, likely derived from high-temperature-perturbation faulting events. It implies that FZ760 accommodated numerous single-event displacement and/or at higher normal stresses and/or in the absence of pore fluid and/or along a more localized slip surface(s). Because graphite is a well-known lubricant, we surmise that the presence of the higher degree graphitized CM within FZ760 will reduce the fault strength and inefficiently accumulate tectonic stress during the seismic cycle at the current depth, and further infer a plausible mechanism for fault propagation at the borehole depth of 590 m during the Mw 7.9 Wenchuan earthquake.

原文英語
文章編號393
期刊Minerals
8
發行號9
DOIs
出版狀態已發佈 - 2018 九月 7

ASJC Scopus subject areas

  • Geotechnical Engineering and Engineering Geology
  • Geology

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