金沙江变质带变质作用时期的确定

    DETERMINATION OF THE AGE OF METAMORPHISM OF THE JINSHA RIVER METAMORPHIC BEIT

    • 摘要: 川藏交界金沙江流域广泛发育一套由前寒武系茶马贡群、古生界、三叠系义敦群组成的区域变质岩系,呈近南北向展布,大体与金沙江在该段的走向一致。本文讨论的金沙江变质带西以玉树—羊拉弧形断裂为界,东至欧巴纳—定曲河—中甸断裂,北起四川省白玉县经巴塘县、得荣县、向南经奔子栏、中甸延入云南省境内。东西宽约40公里、南北长达300余公里。呈近南北向“牛角”形(图1)。其所处大地构造位置按中国地质科学院1978年划分意见属滇藏地槽褶皱区“三江”印支褶皱系。这里地质构造复杂、矿产资源丰富亟待进一步研究开发。

       

      Abstract: The metamorphic rock series developed in the Jinsha River area on the Sichuan-Xizang(Tibet)border has long attracted the attention of the geological circle,and for years various schools have expressed different views on the age and nature of its metamorphism. In this paper,in the light of available geological data on the metamor- phism,magmatism and tectonic movements,the author proposes nine lines of evidence or indications and suggests that the present area experienced at least two phases of important metamorphic events:(i)the first phase took place in the late Hercynian time,starting at the end of the formation of the lower Permian E’aqin Group and terminating prior to the upper Permian deposition,and the metamorphism of this phase may be referred to as the late Hercynian high-pressure type regional metamorphism;(ii) the second phase took place in the period from the Triassic to pre-Pa- leogene,and the metamorphism may be called the Indosinian-Yanshanian regional dynamic metamorphism.The former is the main phase of metamor- phism,on which the latter was superimposed.

       

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