上部地壳的流体作用与大理岩的低温塑性被引量：9

Fluid flow and low temperature plasticity of marble in the upper crustal level.

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摘要本文应用光学显微镜、透射电子显微镜和阴极发光显微镜系统研究了 Waterberg断层带 (纳米比亚 )内粗晶大理岩中发育的构造岩。宏观碎裂结构与微观糜棱状结构是断层构造岩的主要特点。巨大的变形碎屑与弥漫的细小颗粒基质形成了鲜明的反差。广泛发育的压溶缝合线与多阶段方解石细脉遍布构造带不同部位。TEM亚微分析表明 ,细粒基质是由粗大碎屑经过亚颗粒旋转 ,并伴随着局部颗粒边界迁移形成的动态重结晶颗粒。虽然亚颗粒粒度具有简单的峰值分布 (～ 0 .3～0 .4μm) ,但动态重结晶颗粒的粒度却具有较大的变化范围 (0 .1～ 3.0μm )并具有多峰值分布的趋势。 TEM亚微结构 (晶格位错结构 )分析与亚颗粒、动态重结晶粒度、变形双晶宽度统计分析充分证明变形—恢复过程的非稳态特点。结合阴极发光分析阐明在上部地壳环境中 ,方解石大理岩经历脆性变形过程中 ,流体相广泛介入到变形作用中 ,并促进岩石的非稳态脆 -韧性转变与低温塑性的出现。 Optical, TEM and Cathodoluminescence microscopes are applied to study the calcite tectonites from coarse grained marble in the Waterberg fault zone (Namibia). The tectonites are characterized by macroscopic cataclastic and microscopic mylonitic structures. Very huge clasts and diffusive fine grained matrix present an obvious contrast. Highly developed stylolite seams by pressure solution and multi stages of calcite veining are widely distributed in the fault zone. It is shown from TEM analysis that the fine grained matrix materials are mainly derived from the huge clasts by subgrain rotation and local grain boundary migration. The subgrain sizes have a tendency of simple peak distribution (0.3~0.4μm), while the grain sizes of dynamically recrystallized new fine grains vary to a certain extent (0.1~3.0μm), with a tendency of multiple peaks. The TEM submicrostructural analysis, together with the statistical data on grain sizes of sub grains and dynamically recrystallized new fine grains, and twin widths, indicates the unsteady state of the deformation recovery processes. Microstructural and cathodoluminescence analysis of the deformed rocks suggests that fluid phases are widely involved in the brittle ductile deformation in the upper crust. They may contribute to the unsteady transition from brittle to ductile and induce the occurrence of the low temperature plasticity of the rocks. Hydrolytic weakening mechanism dominated by fluid enhanced dislocation activity and recovery processes may best explain the low temperature plasticity of marble in the upper crustal level.

作者刘俊来 Weber K Walter J

机构地区吉林大学地球科学系格廷根大学岩石圈地质与动力学研究所