Sources of the Nanwenhe - Song Chay granitic complex (SW China - NE Vietnam) and its tectonic significance
Sources of the Nanwenhe - Song Chay granitic complex (SW China - NE Vietnam) and its tectonic significance
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DOI：
10.1016/j.lithos.2017.07.017
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发表时间：
2017-10
期刊：
影响因子：
3.5
通讯作者：
Xiaoping Zhou;Jinhai Yu;Jinhai Yu;S. O’Reilly;W. Griffin;Xiaolei Wang;T. Sun
中科院分区：
文献类型：
--
作者：
Xiaoping Zhou;Jinhai Yu;Jinhai Yu;S. O’Reilly;W. Griffin;Xiaolei Wang;T. Sun
南汶河-宋寨杂岩体是一个横跨中国西南部和越南东北部的早古生代大型岩体。它位于扬子、华夏和印支陆块的构造交汇处，因此该杂岩的来源至今仍是个谜。杂岩体为高钾钙碱性过铝S型花岗岩。对该杂岩体中12个花岗质样品进行了LA-ICP-MS锆石U-Pb定年，测得其结晶年龄为436-423 Ma。锆石U-Pb-Hf同位素和地球化学资料表明，南汶河花岗岩可能主要来源于新元古代与峡江群、儋州群类似的变质泥质岩。与此相反，在南中国海南部的宋斋花岗岩可能是来自新元古代变质砂质岩类似的梵净山群和四堡群在扬子地块西南部。杂岩体中含有丰富的继承性锆石，主峰在836-808 Ma，次峰在~ 734 Ma和528-665 Ma。继承锆石的年龄分布模式和Hf同位素组成与扬子地块西南部新元古代-早古生代沉积岩中的碎屑锆石相似，而与华夏地块和印支地块的碎屑锆石不同。因此，南西造山带的基底相当于扬子地块，该杂岩可能代表了华南造山带早古生代造山带的最西端。因此，我们认为扬子地块与华夏地块的边界以及华南板块与国际板块的边界应分别位于南汶河-宋斋地区的东南和西南。
The Nanwenhe - Song Chay complex (NSCC) is a large early Paleozoic pluton straddling the border between SW China and NE Vietnam. It is located at the tectonic junction of the Yangtze, Cathaysia and Indochina blocks so that the source of the complex is still enigmatic. The rocks from the complex are high-K calc-alkaline and peraluminous S-type granite. LA-ICP-MS U–Pb dating of zircons from twelve granitic samples in the complex gives crystallization ages in the range of 436–423 Ma. Zircon U–Pb-Hf isotopes and geochemical data show that the Nanwenhe granites in the northern part of the NSCC probably were mainly derived from Neoproterozoic metamorphic pelites analogous to those in the Xiajiang and Danzhou Groups. In contrast, the Song Chay granites in the southern part of the NSCC were probably derived from Neoproterozoic metamorphic psammites analogous to those in the Fanjingshan and Sibao groups in the southwestern Yangtze Block. The granites from the complex contain abundant inherited zircons with a main peak at 836–808 Ma and subordinate peaks at ~ 734 Ma and 528–665 Ma. The inherited zircons have age distribution patterns and Hf-isotopic compositions similar to those for the detrital zircons from Neoproterozoic to Early Paleozoic sedimentary rocks in the southwestern part of the Yangtze Block, but different from those of the Cathaysia Block and Indochina Block. Therefore, the basement of the NSCC is equivalent to the Yangtze Block, and the complex may represent the westernmost tip of the early Paleozoic orogenic belt in the SCB. We thus assume that the boundaries between the Yangtze Block and the Cathaysia Block and between the SCB and ICB should be located to the southeast and southwest of the Nanwenhe - Song Chay area, respectively.