Petrology and geochronology of the Namche Barwa Complex in the eastern Himalayan syntaxis, Tibet: constraints on the origin and evolution of the north-eastern margin of the Indian Craton
Petrology and geochronology of the Namche Barwa Complex in the eastern Himalayan syntaxis, Tibet: constraints on the origin and evolution of the north-eastern margin of the Indian Craton
复制标题
DOI：
10.1016/j.gr.2011.02.002
复制
发表时间：
2012
影响因子：
6.1
通讯作者：
Zeming Zhang;Xin Dong;M. Santosh;Feng Liu;Wei Wang;Fei Yiu;Zhenyu He;K. Shen
中科院分区：
文献类型：
--
作者：
Zeming Zhang;Xin Dong;M. Santosh;Feng Liu;Wei Wang;Fei Yiu;Zhenyu He;K. Shen
藏南东喜马拉雅构造结的南迦巴瓦杂岩（NBC）一般被解释为大喜马拉雅层序的东北端，包括沿印度大陆北方边缘沿着的新元古代至早古生代沉积地层。野外调查和岩石学研究表明，NBC主要由正片麻岩、副片麻岩、斜长角闪岩和钙硅酸盐岩组成。锆石U-Pb数据表明，该正片麻岩的原岩形成于古元古代晚期。1610 Ma和早古生代约。490-500Ma。斜长角闪岩来自1645 ~ 1590 Ma的镁铁质岩浆岩。从新太古代到早古生代，副片麻岩中锆石的继承性年龄变化很大，主要有4个年龄群：2490 Ma、1640 Ma、990 Ma和480 Ma。钙硅酸盐岩中有锆石，早古生代变质年龄为538 Ma。新生代变质锆石U-Pb年龄在8 ~ 30 Ma之间，最大值为23 Ma。这些，加上以前的结果表明，NBC最初来自安第斯型造山带后，哥伦比亚超大陆组装，并经历了多次改造的格伦维尔，泛非和喜马拉雅造山。与构成喜马拉雅造山带西部和中部高级变质核的大喜马拉雅层序相比，东喜马拉雅构造结的NBC具有不同的物源和构造背景。因此，我们推断NBC最初是中印度构造带东段的一部分。
The Namche Barwa Complex (NBC) in the eastern Himalayan syntaxis, south Tibet, is generally interpreted as the north-eastern extremity of the exposed Greater Himalayan Sequence, comprising Neoproterozoic to early Paleozoic sedimentary strata along the northern margin of the Indian continent. Field and petrological investigations indicate that the NBC consists mainly of orthogneiss, paragneiss, amphibolites and calc-silicate rocks. U–Pb zircon data demonstrate that the protoliths of the orthogneiss formed during late Paleoproterozoic at ca. 1610Ma and also in early Paleozoic at ca. 490–500Ma. The amphibolites were derived from mafic magmatic rocks formed during 1645 to 1590Ma. Zircons in the paragneisses have highly variable inherited zircon ages ranging from the Neoarchean to early Paleozoic, with four major age populations of 2490Ma, 1640Ma, 990Ma and 480Ma. The calc-silicate rock has zircons with early Paleozoic metamorphic age of 538Ma. Almost all the rocks of the NBC have been metamorphosed during Cenozoic with the metamorphic zircon U–Pb ages ranging from 8 to 30Ma and a peak at 23Ma. These, together with previous results suggest that the NBC was originally derived from an Andean-type orogeny following the Columbia supercontinent assembly, and experienced multiple reworking during the Grenvillian, Pan-African and Himalayan orogenies. We conclude that the NBC in the eastern Himalayan syntaxis was derived from different provenance and tectonic setting as compared to those of the Greater Himalayan Sequence which constitutes the high-grade metamorphic core of the western and central Himalayan orogenic belt. We thus infer that the NBC was originally part of the eastern segment of the Central Indian Tectonic Zone.