Development of shape- and lattice-preferred orientations of amphibole grains during initial cataclastic deformation and subsequent deformation by dissolution-precipitation creep in amphibolites from the Ryoke metamorphic belt, SW Japan
Development of shape- and lattice-preferred orientations of amphibole grains during initial cataclastic deformation and subsequent deformation by dissolution-precipitation creep in amphibolites from the Ryoke metamorphic belt, SW Japan
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DOI：
10.1016/j.jsg.2003.09.004
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发表时间：
2004-01-01
影响因子：
3.1
通讯作者：
Kanagawa, K
中科院分区：
文献类型：
--
作者：
Imon, R;Okudaira, T;Kanagawa, K
日本西南部Ryoke变质带的斜长角闪岩最初是通过碎裂作用变形的，随后是溶解-沉淀蠕变作用。最初的碎裂变形产生了较弱的形状择优取向(SPO)和较不发达的角闪石晶格择优取向(LPO)，角闪石晶格择优取向(LPO)较差，nα(近似于a[100])轴散布在面理附近，nGamma或c[001]轴散布在线理周围。在后期的溶解-沉淀蠕变变形过程中，近平行于面理的晶界优先溶解和垂直于面理的同时压实可能产生了近平行于面理的细长棕色角闪石颗粒及其LPO的明显SPO，使得它们的nGamma或c轴散布在线理周围，而nα(近似于α)和nbeta(=b[010])沿垂直于线理的带状展布。同样在这种变形过程中，绿色角闪石以孤立的颗粒或在棕色角闪石颗粒周围的压力阴影区中析出。孤立的绿色角闪石颗粒按照主应力方向成核和各向异性生长，导致这些颗粒的LPO，使得它们的nα(近似于α)方向垂直于面理，nβ(=b)在垂直于线理的面理内，n伽马(或c)轴平行于线理。此外，还有一个关联的SPO。在棕色角闪石颗粒周围的压力阴影区中，绿色角闪石的生长根据主应力方向的不同，发生在语法上或各向异性上。(C)2003爱思唯尔有限公司。保留所有权利。
Amphibolites from the Ryoke metamorphic belt, SW Japan were deformed initially by cataclasis and subsequently by dissolution-precipitation creep. Initial cataclastic deformation produced a rather weak shape-preferred orientation (SPO) of brown amphibole grains with small aspect ratios as well as a poorly developed amphibole lattice-preferred orientation (LPO) with nalpha (approximate to a[100]) axes scattered subnormal to the foliation and ngamma or c[001] axes scattered around the lineation. During later deformation by dissolution-precipitation creep, preferential dissolution at grain boundaries subparallel to the foliation and simultaneous compaction normal to the foliation have likely produced a distinct SPO of elongate brown amphibole grains subparallel to the foliation as well as their LPO such that their ngamma or c axes are scattered around the lineation, while nalpha (approximate to alpha) and nbeta ( = b[010]) are spread along a girdle normal to the lineation. Also during this deformation green amphibole precipitated as isolated grains or in pressure shadow regions around brown amphibole grains. Nucleation and anisotropic growth of isolated green amphibole grains according to the orientations of the principal stress directions roduced an LPO of these grains such that their nalpha (approximate to alpha) are oriented normal to foliation, nbeta (= b) within the foliation normal to the lineation and ngamma (or c) axes are parallel to the lineation. In addition, there is an associated SPO. Growth of green amphibole in pressure shadow regions around brown amphibole grains occurs either syntaxially or anisotropically according to the orientations of the principal stress directions. (C) 2003 Elsevier Ltd. All rights reserved.