Tribochemical wearing in S-C mylonites and its implication to lithosphere stress level
Tribochemical wearing in S-C mylonites and its implication to lithosphere stress level
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S-C糜棱岩的摩擦化学磨损及其对岩石圈应力水平的影响
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发表时间：
2002
期刊：
影响因子：
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通讯作者：
H. Nagahama
中科院分区：
文献类型：
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作者：
N. Nakamura;H. Nagahama
本文提出了一种揭示S-C糜棱岩（糜棱岩中具有c -表面的糜棱岩的s -叶理）中c -表面作为局部高剪切应变带的脆性起源的新方法。全球范围内的剪切带宽度(W)和位移(D)数据表明，韧性糜棱岩的W/D比值恒定在10−0.3，而脆性碎裂岩的W/D比值在10−1 ~ 10−3之间变化，表明该比值是区分韧性剪切带和脆性剪切带的诊断指标。日本东北部Hatagawa剪切带花岗质S-C糜棱岩沿c面剪切位移矿物的新测量W-D数据被添加到世界W-D目录中，并绘制在高W/D比为10−1.5的脆性原点上。根据这一结果和热液条件下磨损形成的摩擦化学磨损理论，S-C糜棱岩中的C-表面可能是在岩石圈应力水平约300 MPa、温度为400℃、花岗岩水作用下的碎裂变形形成的。这一结果表明，在S-C糜棱岩地层深处，变形主要是塑性的，岩石圈应力水平很高。
A new approach for revealing the brittle origin of C-surfaces as localized high shear strain zones in S-C mylonites (mylonites with C-surfaces cutting through a mylonitic S-foliation) is presented. A compiled worldwide catalog of width (W) and displacement (D) data for shear zones indicates that ductile mylonites show a constant W/D ratio of 10−0.3 and ratios of brittle ‘cataclasites’ vary in magnitude from 10−1 to 10−3, implying that the ratio is a diagnosis for discriminating ductile and brittle shear zones. A newly measured W-D data of shear displaced minerals along C-surfaces in granitic S-C mylonites from the Hatagawa shear zone in northeast Japan is added on the worldwide W-D catalog, being plotted on a brittle origin with the high W/D ratio of 10−1.5. Using this result and a tribochemical wear theory which accounts for wear formation under hydrothermal conditions, C-surfaces in the S-C mylonite might have been formed by cataclastic deformation under the lithosphere stress level of ca. 300 MPa at temperature of 400°C with water for granite. This result suggests a high lithosphere stress level at the depth of the S-C mylonite formation where deformation is predominantly plastic.