The occurrence of graphite-bearing fault rocks in the Atotsugawa fault system, Japan: Origins and implications for fault creep
The occurrence of graphite-bearing fault rocks in the Atotsugawa fault system, Japan: Origins and implications for fault creep
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DOI：
10.1016/j.jsg.2011.10.011
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发表时间：
2012-05
影响因子：
3.1
通讯作者：
K. Oohashi;T. Hirose;Kenta Kobayashi;T. Shimamoto
中科院分区：
文献类型：
--
作者：
K. Oohashi;T. Hirose;Kenta Kobayashi;T. Shimamoto
断层带中的石墨虽然是一种众所周知的固体润滑剂，但却很少受到关注。本文报道了日本中部Atotsugawa断层系断层带中存在丰富的石墨。断层岩的细观和微观观察揭示了断裂带中碳的两个富集过程。一种是压力溶解过程或一般的扩散传质，其从岩石中去除水溶性矿物如石英和碳酸盐，导致不溶性矿物（包括碳）的富集。另一个过程是石墨从高温富碳流体中沉淀出来，在碎裂断层带内形成石墨填充裂缝。这两个过程导致的浓度，高达12重量%的石墨，在Atotsugawa断层带，相比之下，0至3重量%的含碳物质的寄主岩石。该浓度足够高，使得石墨在宽范围的滑动率下影响摩擦性能。石墨的存在可能为Atotsugawa断层系统西部的低电阻率、微震模式和断层蠕动沿着提供解释。石墨作为断层的弱化剂和稳定剂应受到更多的关注。
Graphite in fault zones has received little attention even though it is a well-known solid lubricant that could affect frictional properties of faults dramatically. This paper reports the presence of abundant graphite in fault zones of the Atotsugawa fault system, central Japan. Mesoscopic and microscopic observations of fault rocks revealed two processes of carbon enrichment in fault zones. One is a pressure solution process or diffusive mass transfer in general which removes water-soluble minerals such as quartz and carbonates from rocks, resulting in the enrichment of insoluble minerals including carbon. The other process is precipitation of graphite from a high-temperature carbon-rich fluid, forming graphite filling fractures within cataclasitic fault zones. The two processes have led to the concentration, up to 12 wt% of graphite, in the Atotsugawa fault zones, compared to 0 to 3 wt% of carbonaceous materials in the host rocks. This concentration is high enough for graphite to affect frictional properties at wide range of slip rates. The presence of graphite may provide an explanation for the low resistivity, the patterns of microearthquakes and fault creep along the western part of the Atotsugawa fault system. Graphite should receive more attention as a weakening and stabilizing agent of faults.