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Studies on deformation mechanisms of regional metamorphic rocks by means of microfabric analyses

区域变质岩变形机制的微结构分析研究

基本信息

批准号：
61420015
负责人：
YOSHIDA Shizuo
金额：
$ 14.85万
依托单位：
University of Tokyo
依托单位国家：
日本
项目类别：
Grant-in-Aid for General Scientific Research (A)
财政年份：
1986
资助国家：
日本
起止时间：
1986 至 1988
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-61420015/
关键词：
Metamorphic rock Slate Ophiolite Fabric Strain 変形メカニズム

项目摘要

The main purpose of this study is to know processes and mechanisms of plastic deformation of rocks by means of quantitative fabric analyses that are carried out by the x-ray texture goniometer. First, we devised and developed a computer program for measurement and data-processing through many trial experiments on micas, chlorite, hornblende, olivine, and quartz in deformed rocks. We established a highly reliable method which gives more accruate values than those from current methods, and only takes a half to one third of measuring time on a current apparatus. Results of measurement are represented quantitatively in terms of types and degrees of preferred orientation. Main results are as follows. 1. As deformation mechanisms for slates, pressure solution is dominant at a lower temperature condition, while preferred recrystallization is dominant at a higher temperature condition. The strain ellipsoids are oblate and are correlative to S fabric. 2. As deformation mechanisms for the high P/T Sambagawa metamorphic rocks, dislocation creep together with preferred recrystallization is dominant. The strain ellipsoids are generally prolate. 3. As deformational mechanism for low P/T Ryoke metamorphic rocks, diffusion creep is dominant. The strain ellipsoids are generally prolate. 4. The deformation of ultramafic tectonites, which may give a clue to know the deformational mechanism in the upper mantle, is inferred to be due to dislocation creep from the fabric pattern of olivine. In future, measurements should be carried for rocks collected from wider areas, and the relationship between amounts of strain and fabric types should be established. Comparative studies on deformation mechanisms among main orogenic belts in the world are also important to know the machanisms of plastic deformation in the deeper crust and upper mantle.

本研究的主要目的是通过X射线结构测角仪进行定量组构分析，了解岩石塑性变形的过程和机制。首先，我们设计和开发了一个计算机程序，用于测量和数据处理，通过对变形岩石中的云母、云母、角闪石、橄榄石和石英的多次试验。我们建立了一种高可靠性的方法，它比现有的方法得到更多的累积值，并且在现有的仪器上只需要一半到三分之一的测量时间。测量结果以择优取向的类型和程度定量表示。主要结果如下。1.板岩的变形机制在较低温度条件下以压溶为主，而在较高温度条件下以择优再结晶为主。应变椭球体呈扁球形，与S组构相关。2.高P/T桑巴川变质岩的变形机制以位错蠕变和择优重结晶为主。应变椭圆体通常是扁长的。3.低P/T Ryoke变质岩的变形机制以扩散蠕变为主。应变椭圆体通常是扁长的。4.超镁铁质构造岩的变形可能是由于位错蠕变引起的，这可能为认识上地幔的变形机制提供了线索。今后，应在更大范围内对岩石进行测量，并建立应变量与组构类型之间的关系。世界主要造山带变形机制的对比研究，对认识地壳深部和上地幔的塑性变形机制也有重要意义。