西藏察隅地区古元古代德玛拉岩群的特征

西藏察隅地区出露一套由片岩、片麻岩、变粒岩夹斜长角闪岩及大理岩等组成的中深变质岩系。通过岩石学、岩石地球化学、同位素地质学及原岩建造的研究，并采用构造—岩层—事件方法的分析与对比，新建立了墨色同岩组和蛇躲岩组两个岩石地层单位，统称为德玛拉岩群。依据Ｓｍ Ｎｄ法年龄２１４５～２２６４Ｍａ将其时代确定为古元古代。该岩群与印度马德拉斯和斯里兰卡形成于２３００～２１００Ｍａ的孔达岩系十分相似，可能是冈瓦纳古陆核北缘的一套浅海相沉积

Paleoproterozoic Demala Group-complex in the Zayu Area, Tibet

A medium and high grade metamorphic series is exposed in the Zayu area, Tibet. It consists of schist, gneiss and granulitite （leptynite） with amphibolite and marble. On the basis of petrological, geochemical and isotope geological studies and characteristics of protoliths combined with the integrated comparison and analysis of structure strata events, two lithostratigraphic units the Mosetong and Shedu formation complexes have been newly established, which are called by a joint name the Demala Group complex. According to its Sm Nd ageof 2 264～2 145 Ma, it is considered to be Paleoproterozoic in age. The rocks of this group complex very closely resemble khondalite formed 2 300～2 100 Ma ago in Madras of India and Sri Lanka, so it is possibly a sequence of neritic deposits on the northern margin of the nucleus of Gondwana.