Thermal decomposition of serpentine during coseismic faulting: Nanostructures and mineral reactions
Thermal decomposition of serpentine during coseismic faulting: Nanostructures and mineral reactions
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DOI：
10.1016/j.jsg.2010.09.009
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发表时间：
2010-10
影响因子：
3.1
通讯作者：
C. Viti;T. Hirose
中科院分区：
文献类型：
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作者：
C. Viti;T. Hirose
本文报道了在高速摩擦仪中以地震滑动速率（1.1 m/s）变形的含锑蛇纹岩的详细特征。对滑移带（200 μm厚）的微/纳米结构研究显示了一种带状排列，具有明显不同强度的层位紧密并置，分别由无定形到低结晶相（大块无水成分接近起始叶蛇纹石）和高度结晶的镁橄榄石和无序顽火辉石组合（尺寸为200 nm，具有类似宝石的纳米结构）组成。滑动带还承载微/纳米尺寸的Cr-磁铁矿颗粒，相对于滑动面以低角度排列，并从寄主蛇纹岩继承。总体观察表明，滑动表面上的粗糙处的摩擦加热引起温度升高至820-1200 °C（与闪温理论一致），导致蛇纹石完全脱水和非晶化，随后镁橄榄石和顽火辉石结晶（在变形后静态条件下）。这项研究的结果可能提供重要的钥匙，充分理解的力学行为和可能的地球动力学作用的蛇纹岩主办的断层通过地震周期。
This paper reports a detailed characterization of an antigorite-bearing serpentinite, deformed at seismic slip-rate (1.1 m/s) in a high-velocity friction apparatus. Micro/nanostructural investigation of the slip zone (200 μm thick) revealed a zonal arrangement, with a close juxtaposition of horizons with significantly different strength, respectively consisting of amorphous to poorly-crystalline phases (with bulk anhydrous composition close to starting antigorite) and of highly-crystalline assemblages of forsterite and disordered enstatite (200 nm in size and in polygonal-like nanotextures). The slip zone also hosts micro/nanometre sized Cr-magnetite grains, aligned at low angle with respect to the slipping surface and inherited from the host serpentinite. Overall observations suggest that frictional heating at asperities on the slipping surface induced a temperature increase up to 820–1200 °C (in agreement with flash temperature theory), responsible for serpentine complete dehydration and amorphization, followed by crystallization of forsterite and enstatite (under post-deformation, static conditions). The results of this study may provide important keys for the full comprehension of the mechanical behaviour and of the possible geodynamical role of serpentinite-hosted faults through the seismic cycle.