Deformation fabrics of natural blueschists and implications for seismic anisotropy in subducting oceanic crust
Deformation fabrics of natural blueschists and implications for seismic anisotropy in subducting oceanic crust
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DOI：
10.1016/j.pepi.2013.06.011
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发表时间：
2013-09
影响因子：
2.3
通讯作者：
Daeyeong Kim;I. Katayama;K. Michibayashi;T. Tsujimori
中科院分区：
文献类型：
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作者：
Daeyeong Kim;I. Katayama;K. Michibayashi;T. Tsujimori
俯冲带尤其在俯冲板块内部产生强烈的应力，并形成特殊的高压低温环境。因此，蓝片岩的研究对于认识俯冲带的活动应力和揭示其丰富的含水相的地流体循环具有重要意义。通过对自然变形蓝片岩和实验变形蓝片岩的结构分析，揭示了蓝片岩对俯冲洋壳地震各向异性和地震活动性的影响。第一个子项目研究了加利福尼亚迪亚波罗山脉新伊德里亚蛇纹岩体中天然蓝片岩中蓝闪石和钙辉石的流变学对比。反面体-亚面体蓝水晶表现出较强的晶体偏好取向（CPOs），晶粒尺寸小，晶界不规则，长径比高，表明可能是位错蠕变导致的恢复和动态再结晶。自面体到亚面体的花岗岩由于棱角晶界或直晶界的刚体旋转而变形。富蓝透石层与富蓝透石层相比，蓝透石和lawsonite的纵横比更高，片理角更小，cpo更强，地震各向异性更高，表明应变局部化到富蓝透石层。另一方面，与石榴石相比，蓝闪石具有更高的纵横比、更小的片理角、更强的cpo和更高的地震各向异性。
Subduction zone could generate strong stresses especially within subducting slab and also it makes special high pressure and low temperature environments. Ergo study on blueschist is important to understand active stresses in subduction zone and in addition to reveal geofluid circulations owing to abundant hydrous phases in it. Fabric analyses of naturally and experimentally deformed blueschists were investigated to delineate its implications for seismic anisotropy and source of seismicity in subducting oceanic crust. The first subproject dealt rheological contrast of glaucophane and lawsonite in natural blueschist from the New Idria serpentinite body, Diablo Range, California. Anhedral to subhedral glaucophane shows strong crystal-preferred orientations (CPOs) with small grain size, irregular grain boundary, and high aspect ratio, indicating recovery and dynamic recrystallization possibly accommodated by dislocation creep. Euhedral to subhedral lawsonite deforms by rigid body rotation due to angular or straight grain boundary. Glaucophane-rich layer contains higher aspect ratio, lower angle to foliation, stronger CPOs, and higher seismic anisotropy of glaucophane and lawsonite than those in lawsonite-rich layer, suggesting the strain localization into the glaucophane-rich layer. On the other hand, glaucophane has higher aspect ratio, lower angle to foliation, stronger CPOs, and higher seismic anisotropy than lawsonite,