Style of fluid flow and deformation in and around an ancient out‐of‐sequence thrust: An example from the Nobeoka Tectonic Line in the Shimanto accretionary complex, Southwest Japan
Style of fluid flow and deformation in and around an ancient out‐of‐sequence thrust: An example from the Nobeoka Tectonic Line in the Shimanto accretionary complex, Southwest Japan
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古代无序逆冲断层内部及其周围的流体流动和变形类型：以日本西南部四万十增生杂岩延冈构造线为例
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发表时间：
2009
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通讯作者：
W. Soh
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作者：
H. Mukoyoshi;T. Hirono;H. Hara;K. Sekine;N. Tsuchiya;A. Sakaguchi;W. Soh
为了了解序列外逆冲断层（OST）的变形特征和沿其沿着流动的流体类型，我们调查了日本西南部四万十增生杂岩中被解释为深层OST（7-9 km）的野冈构造线。 下盘剪切带在沿着走向方向上不仅在厚度（100 ~ 300 m）上存在显著差异，而且在岩性和矿脉发育方面也存在显著差异。 这些变化可能主要反映了岩性的差异;也就是说，砂岩为主的剪切带具有大量在微裂缝中沉淀的矿脉，相对较厚，而页岩为主的剪切带具有少量矿脉和指示高压孔隙流体的纹理，较薄。通过与浅层OST（3-5 km）的特征比较，我们得出结论，浅层OST经历了反复的脆性破坏，快速滑动和集中的流体流动，而深层OST经历了脆性和韧性变形，随后是各种风格的流体流动，这取决于岩性。
To understand the characteristics of deformation of an out‐of‐sequence thrust (OST) and the style of fluid flow along it, we investigated the Nobeoka Tectonic Line, which has been interpreted as a deep OST (7–9 km), in the Shimanto accretionary complex, Southwest Japan. The shear zone in the footwall differs significantly in the along‐strike direction not only in thickness, which varied from 100 to 300 m, but also in lithology and mineral vein development. These variations might reflect primarily differences in lithology; that is, the sandstone‐dominant shear zone with a large amount of mineral veins precipitated in microcracks is relatively thick, whereas the shale‐dominant shear zone with a small amount of veins and with textures indicating highly pressurized pore fluid, is thinner. By comparison with characteristics of a shallow OST (3–5 km), we conclude that the shallow OST has experienced repeated brittle failure with rapid slip and focused fluid flow whereas the deep OST has experienced both brittle and ductile deformation, followed by fluid flow of various styles, depending on the lithology.