杨天南, 徐宏顺. 2008: 通过构造岩鉴别岩石动态重结晶的机制. 地质通报, 27(9): 1459-1467.
    引用本文: 杨天南, 徐宏顺. 2008: 通过构造岩鉴别岩石动态重结晶的机制. 地质通报, 27(9): 1459-1467.
    YANG Tian-nan, XU Hong-shun. 2008: Mechanisms of dynamic recrystallization: recognition from natural tectonites. Geological Bulletin of China, 27(9): 1459-1467.
    Citation: YANG Tian-nan, XU Hong-shun. 2008: Mechanisms of dynamic recrystallization: recognition from natural tectonites. Geological Bulletin of China, 27(9): 1459-1467.

    通过构造岩鉴别岩石动态重结晶的机制

    Mechanisms of dynamic recrystallization: recognition from natural tectonites

    • 摘要: 岩石如书,包含着丰富的地球演化信息。通过破解这本天书,地质学家得以了解发生在地球内部的地质过程。构造岩中的显微构造是“写在岩石中的变形过程”。通过显微构造观察,可以了解岩石矿物的变形机理。以天山造山带内发育的糜棱岩为具体实例,介绍了中、下地壳层次变形岩石动态重结晶的机理及形成的相关显微构造的特点。由于构造岩均是经历过重结晶作用的产物,显微观察只能揭示变形矿物重结晶的机制。在中、下地壳层次,矿物动态重结晶的主要机理分为3种(从低温到高温):膨胀鼓出(BLG,又称膨凸)、亚晶粒旋转(SGR)和高温颗粒边界迁移(GBM)。这3种方式形成各具特色的显微构造:BLG形成近等粒交叉舌状构造;SGR产生定向排列的拉长新颗粒条带;而GBM造成典型的具不规则状颗粒边界、大小悬殊的新颗粒组合、颗粒内部波状消光不明显的显微构造。除了温度条件外,应变速率对动态重结晶机制也有明显的影响。在显微构造观察过程中,详细、全面应该是最重要的原则。

       

      Abstract: As the major research target of geologists, “rock is like book” (K-K-K), which contains abundant information of the Earth’s evolutionary history. Microstructure in tectonites is a “deformation process written in stone”. Observations of microstructure may reveal the deformation mechanism of associated rocks and minerals. Take for example mylonite occurring in the Tianshan orogenic belt, the authors introduce the dynamic recrystallization mechanism of deformed rocks at the middle and lower crustal levels and features of related microstructures. As tectonites are all the product of recrystallization, they can only reveal the mechanism of deformed minerals. At the middle and lower crustal levels three major dynamic recrystallization mechanisms of minerals (from low to high temperatures): bulging (BLG), subgrain rotation (SGR), and high-temperature grain boundary migration (GBM), which result in formation of different microstructures. The typical microstructure formed by BLG is featured by interlobated fine and equigranular structure. SGR gives rise to ribbons consisting of oriented elongated new grains. GBM forms an assemblage of typical new grains with irregular grain boundaries and greatly varied grain size and microstructure with indistinct wavy extinction inside grains. Besides temperature conditions, strain rates also have significant effect on the dynamic recrystallisation mechanism. “Detail” and “completeness” should be the main principles in microtectonic observations and structural data interpretation.

       

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