柴达木盆地北缘“达肯大坂群”的再厘定

    Redefinition of the "Dakendaban Group" on the northern margin of the Qaidam basin

    • 摘要: 柴达木盆地北缘原划为古元古代的“达肯大坂群”出露相当广泛,不仅包含了变质程度不同的表壳岩,而且包括了时代迥然不同的变质深成侵入体。原“达肯大坂群”至少有四种类型的岩石组合:其中德令哈杂岩形成时代最老,为古元古代早期的产物;厘定后所称的达肯大坂岩群为一套中至高级变质、并以副变质岩为主的表壳岩系统,推测其形成时代为古元古代晚期至中元古代;第三套岩石组合为花岗片麻岩,主要形成于新元古代早期,不属于沉积地层范畴,其中大量出现榴辉岩包体;榴辉岩除以规模较小的独立包体形式赋存于新元古代花岗片麻岩中外,还和大理岩、石英岩、含石榴石片岩共生在一起,在花岗片麻岩中形成规模较大的残块,这些榴辉岩及与其共生的表壳岩共同构成鱼卡河或沙柳河岩群。

       

      Abstract: The strata on the northern margin of the Qaidam basin were originally assigned to the Paleopro-terozoic"Dakendaban Group".It,exposed quite extensively,includes not only supracrustal rocks of dif-fering metamorphic grades but also metamorphosed plutons of utterly different ages.Recent study indicates that it comprises at least four suites of rock associations.The first suite is called the Delingha complex,which is the oldest,being the early Paleoproterozoic product.The second one is the redefined so-called Dakendaban Group-complex,which is a suite of medium-to high-grade metamorphic supracrustal rocks dominated by parametamorphic rocks and is inferred to be of late Paleoproterozoic to Mesoproterozoic age.The third suite is granite gneiss,formed mainly in the early Neoproterozoic and not belonging to sedimen-tary strata,in which there appear large quantities of eclogite inclusions.The last suite is eclogites,which occur as separate small inclusions or large relics in the Neoproterozoic granite gneiss and also are associated with marble,quartzite and garnet-bearing schist;these eclogites and their associated supracrustal rocks com-bine to form the Iqe River or Shaliu River Group-complex.

       

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