陕西商南秦岭群闪岩系的原岩恢复与多期变质作用

    RECONSTRUCTION OF THE PROTOLITHS AND POLYPHASE METAMORPHISM OF THE AMPHIBOLITE SERIES OF THE QINLING GROUP IN SHANGNAN,SHAANXI

    • 摘要: 商南松树沟超镁铁质岩体侵位于秦岭群下部之闪岩系中。自中元古代以来,秦岭群及其中的闪岩经历过多期变形和变质作用,查其形成历史自然很不容易。尽管过去有很多岩石学家对闪岩系中的榴闪岩深感兴趣,但却无人探讨过它的成因。本文作者旨在抛砖引玉,拟从榴闪岩入手,着重讨论闪岩的原岩性质和多期变质的条件,同时也说明我们对秦岭群时代的一些认识。一、闪岩的岩石类型及其特征

       

      Abstract: The amphibolite series in the middle and lower parts of the Qinling Group in Shangnan, Shaanxi, consists of plagioclase amphiboJite and augen and massive garnet amphibolite. All the rocks exhibit the characteristics of oceanic tholeiite, and the garnet amphibolite resulted from retrogressive metamorphism of eclogite. On the basis of a study of the mineralogy and textures of the rocks, the authors have distinguished three episodes of metamorphism. In the Proterozoic, basalts were metamorphosed into amphibolites. Then during the early Paleozoic the rocks underwent metamorphism of high-pressure epidote amphibolite facies together with eclogites and ultramafic rocks that were emplaced subsequently, with the result that the diagnostic mineral glaucophane formed in large quantities. During the late Paleozoic, the rocks were transformed by superimposition of metamorphism of greenschist facies. It has been ascertained now that there might exist an ophiolite suite in the vicinity of Songshugou, which deserves further study.

       

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