Repeated coseismic infiltration of meteoric and seawater into deep fault zones: a case study of the Nojima fault zone, Japan
Repeated coseismic infiltration of meteoric and seawater into deep fault zones: a case study of the Nojima fault zone, Japan
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DOI：
10.1016/j.chemgeo.2003.08.010
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发表时间：
2003-12
期刊：
影响因子：
3.9
通讯作者：
A. Lin;N. Tanaka;S. Uda;M. Satish-Kumar
中科院分区：
文献类型：
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作者：
A. Lin;N. Tanaka;S. Uda;M. Satish-Kumar
流体对活动断裂和剪切带的渗透作用通常是在中上地壳环境中研究的。循环流体将粘土和碳酸盐等细粒沉积物沉积到断裂带的裂缝中。这种充满裂缝的细粒材料、方解石脉和氧化/风化的开放裂缝在日本野岛断裂带从近地表到1800米深的钻芯中都能很好地观察到，该断裂带触发了1995年的神户7.2级地震。粉末X射线衍射分析表明，充填裂隙的细粒物质主要由菱铁矿、方解石、浊沸石和花岗岩的细粒碎屑组成。细粒物质和方解石脉中碳酸盐物质的同位素分析表明，δ13C(Smow)值在19.3‰~27.7‰之间变化，δ13C(Pdb)值在−4.6‰到−18.5‰之间变化，与典型的大气和海水相一致。10个方解石脉样品的14C年龄范围为35.0KYR B.P.~(14)C数据表明，这些充满裂缝的细粒物质、方解石脉和棕色开口裂缝是在过去35-60KYR期间，含O2-和CO2的大气和海水反复向下渗入Nojima深部断裂带而形成的。提出了地震断层抽吸抽水模型，解释了地震断裂过程中潜水的快速变化将地下水带入深部断裂带的原因。
Fluid infiltration into active faults and shear zones is usually studied in middle to upper crustal environment. Circulating fluids deposit fine-grained sediments like clay and carbonate material into cracks within the fault zone. Such crack-fill fine-grained material, calcite veins, and oxidized/weathered open cracks are well observed in the drill cores, from near-surface to a depth of 1800 m, in the Nojima fault zone, Japan, which triggered the 1995 M7.2 Kobe earthquake. Powder X-ray diffraction analysis indicates that the crack-fill fine-grained materials are mainly composed of siderite, calcite, laumontite, and fine-grained clasts of granitic rock. Isotopic analyses of carbonate material within the fine-grained materials and calcite veins reveal variable δ13C (SMOW) values ranging from 19.3‰ to 27.7‰, and δ13C (PDB) values of −4.6‰ to −18.5‰, which are consistent with those of typical meteoric and seawater.14C dates of 10 calcite vein samples range from 35.0 to 58.4 kyr B.P. Geological, petrological, stable isotopic, and14C data suggest that these crack-fill fine-grained materials and calcite veins and brown open cracks were developed by the repeated infiltration of O2- and CO2-bearing meteoric and seawater downward into the deep Nojima fault zone during the last 35–60 kyr. We propose a seismic fault suction-pumping model to interpret the infiltration of subsurface waters being carried down into the deep fault zone by rapid potential change during episodes of seismic faulting.