Rheological contrast between glaucophane and lawsonite in naturally deformed blueschist from Diablo Range
Rheological contrast between glaucophane and lawsonite in naturally deformed blueschist from Diablo Range
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Diablo Range 自然变形蓝片岩中蓝闪石和硬钠石的流变对比
DOI：
10.1111/iar.12003
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发表时间：
2013
期刊：
影响因子：
--
通讯作者：
Tsujimori T
中科院分区：
文献类型：
--
作者：
Kim D.;Katayama I.;Michibayashi K.;Tsujimori T
本文研究了Diablo山脉新伊德里亚蛇纹岩体中的一种钙辉石蓝片岩的变形微观结构，以阐明钙辉石和钙辉石这两种俯冲洋壳在相对低温下的主要矿物组合的流变行为。小晶粒尺寸、不规则晶界和高长径比的晶优取向（CPOs）的发育表明变形机制可能是位错蠕变导致的恢复和动态再结晶，而铁榴石的变形机制是基于棱角晶界或直晶界的自面体晶粒的刚体旋转。富蓝透石层中两种矿物的高长宽比、较低的叶理角和较强的cpo表明应变局部化到富蓝透石层中。此外，富蓝绢石层的织物强度（晶体排列程度）和地震各向异性都高于富lawsonite层，这与微观结构分析相一致。因此，我们所有的结果都暗示蓝片岩的流变行为和地震各向异性的主要作用是蓝绢石而不是滑石。
Deformation microstructures for a lawsonite blueschist from the New Idria serpentinite body, Diablo Range, are investigated to clarify rheological behaviors of glaucophane and lawsonite, which are main mineral assemblages of subducting oceanic crust at relatively cold geotherm. Developments of crystal‐preferred orientations (CPOs) with small grain size, irregular grain boundary and high aspect ratio of glaucophane indicate deformation mechanism as recovery and dynamic recrystallization possibly accommodated by dislocation creep, while lawsonite deforms by rigid body rotation based on euhedral grains with angular or straight grain boundaries. Higher aspect ratios, lower angle to foliation, and stronger CPOs of both minerals in the glaucophane‐rich layer rather than those in the lawsonite‐rich layer suggest the strain localization into the glaucophane‐rich layer. Additionally fabric strength (the degree of crystal alignment) and seismic anisotropy are higher in the glaucophane‐rich layer than that of the lawsonite‐rich layer, which is consistent with the microstructural analyses. All our results imply, therefore, the dominant role of glaucophane rather than lawsonite for rheological behavior and seismic anisotropy of blueschist.