Quartz lattice preferred orientation patterns and static recrystallization: Natural examples from the Ryoke belt, Japan
Quartz lattice preferred orientation patterns and static recrystallization: Natural examples from the Ryoke belt, Japan
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DOI：
10.1130/g22430.1
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发表时间：
2006-07
期刊：
影响因子：
5.8
通讯作者：
Miharu Otani;S. Wallis
中科院分区：
文献类型：
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作者：
Miharu Otani;S. Wallis
石英c轴晶格择优取向（LPO）模式已被广泛用于分析中地壳韧性变形的不同方面。然而，尽管在高级变质带中普遍存在退火显微结构，静态重结晶对这种石英LPOs的影响尚不清楚。从龙轭变质带的女田地区沿沿着几公里的剖面采集了一套石英片岩样品，这些样品到达造山后的新城英云闪长岩。样品显示出晶粒尺寸的增加和微观结构的变化，例如晶界的拉直和石英中石英夹杂物的形成，这些石英夹杂物代表与接触变质作用有关的退火。与清晰的微观结构变化相反，石英c轴LPO图案即使在强退火后也仅显示出非常小的修改。这一结果意味着，石英LPO模式不应该被抹杀的静态重结晶和石英丰富的构造岩，缺乏这种LPO模式变形的过程以外的位错蠕变。在高级岩石中，可能的过程是熔体迁移和扩散蠕变辅助的晶界滑动，这两者都具有牛顿流变学的特征。
Quartz c-axis lattice preferred orientation (LPO) patterns have been widely used to analyze different aspects of mid-crustal ductile deformation. However, despite the common presence of annealed microstructures in high-grade metamorphic belts, the effects of static recrystallization on such quartz LPOs are unclear. A suite of samples of quartz schist from the Nukata area of the Ryoke metamorphic belt was collected along profiles of several kilometers that reach the postorogenic Shinshiro tonalite. The samples show an increase in grain size and changes in microstructure, such as straightening of grain boundaries and formation of quartz-in-quartz inclusions that represent annealing related to contact metamorphism. In contrast to the clear microstructural changes, quartz c-axis LPO patterns show only very minor modifications even after strong annealing. This result implies that quartz LPO patterns should not be obliterated by static recrystallization and quartz-rich tectonites that lack such LPO patterns deformed by processes other than dislocation creep. Likely processes in high-grade rocks are grain boundary sliding assisted by melt migration and diffusion creep, both of which are characterized by Newtonian rheologies.