江西区域变质岩及其变质作用

    REGIONAL METAMORPHIC ROCKS AND THEIR METAMORPHISM IN JIANGXI

    • 摘要: 江西地处我国东南部,横跨两个一级构造单元,即北部属扬子准地台区和中、南部位于华南褶皱系,大致以萍乡—广丰深断裂为界。具有构造活动强烈、岩浆活动频繁、沉积作用多样、成矿条件优越等特色。地壳成长经历了多旋回、多阶段的构造发展演化,明显的大的地壳运动有:晋宁运动、加里东运动、华力西—印支运动和燕山运动,伴随每次构造运动有不同程度的变质作用产生,并形成了不同类型的变质岩石。区域变质岩石是省内

       

      Abstract: Jiangxi extends across two first-order tectonic units, the Yangtze paraplatform region in the north and the South China fold system in the south. Two metamorphic rock series exist there, which respectively formed in the Jinningian and Caledonian folding orogenic movements. In the folding orogenic phase of the early geosynclinal reversion, occurred dynamic-pressure metamorphism of the greenstone-facies sericite-albite type, which is also referred to as "Ⅰ"-type metamorphism. It is of areal distribution, belonging to this type of metamorphism. In the block-faulting orogenic phase of the geosynclinal reversion, occurred dynamothermal metamorphism of the amphibolite facies. It is of zonal or domal distribution, belonging to the polymetamorphism, but the facies changes greatly; stress and heat are the compound factor responsible to this type of metamorphism. It is mostly distributed in uplift zones of a geosyncline, in areas with distinct thermal anomalies along fractures. The heat was derived from deep-seated magmas or regenerated magmas. It is also called "Ⅱ"-type metamorphism. The "Ⅰ" type occurred before the "Ⅱ" type. In the "Ⅱ"-type metamorphism one may recognize two kinds of metamorphism: one is low-pressure metamorphism of the andalusite-silimanite type and the other is moderate-pressure metamorphism of the kyanite (-staurolite)-silimanite type. The former is more typical. In the stage of platform development, regional metamorphism in the main ceased; while in the stage of the activity of continental margins, crustal movements reactivated and contact metamorphism dominated by thermal activity of magmas was widely developed. Thus the continental crust or granites in Jiangxi province formed finally.

       

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