Cambrian granitic gneiss within the central Qiangtang terrane, Tibetan Plateau: implications for the early Palaeozoic tectonic evolution of the Gondwanan margin
Cambrian granitic gneiss within the central Qiangtang terrane, Tibetan Plateau: implications for the early Palaeozoic tectonic evolution of the Gondwanan margin
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DOI：
10.1080/00206814.2016.1141329
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发表时间：
2016-02
影响因子：
2.6
通讯作者：
Yiming Liu;Cai Li;Chao-Ming Xie;Jian‐Jun Fan;Hao Wu;Qingyuan Jiang;Xin Li
中科院分区：
文献类型：
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作者：
Yiming Liu;Cai Li;Chao-Ming Xie;Jian‐Jun Fan;Hao Wu;Qingyuan Jiang;Xin Li
摘要 青藏高原位于喜马拉雅-高山造山带东部，以往的研究主要集中在蛇绿岩和高压变质带上，而对青藏高原基底的研究相对较少。藏北南羌塘地体杜古尔地区出露的寒武系花岗质片麻岩，锆石激光烧蚀电感耦合等离子体质谱（LA-ICP-MS）U-Pb年龄为502-492 Ma，为了解南羌塘地体内可能存在基岩提供了线索。花岗片麻岩在地球化学上与高 K、钙碱性 S 型花岗岩相似，片麻岩内锆石的 Hf 同位素分析得出负 εHf(t) 值（–7.4 至 – 1.1）和旧锆石 Hf 模型年龄（TDMC = 1757–1406 Ma）。这些花岗质片麻岩是由古代泥质岩部分熔融而生成的，所产生的熔体受到少量地幔衍生物质的污染。结合我们的新数据和之前的研究，我们得出结论，这些寒武纪花岗质片麻岩是在泛非构造运动之后的碰撞后构造环境中发育的。这表明南羌塘地体可能具有与拉萨、喜马拉雅、保山、贡山、腾冲地体相同的早古生代结晶基底。
ABSTRACT The Tibetan Plateau is located in the eastern Himalayan–Alpine orogen, an area where previous research has focused on ophiolites and a high-pressure metamorphic belt, whereas comparatively little research has been undertaken on the Tibetan basement. Cambrian granitic gneiss crops out in the Duguer area of the South Qiangtang terrane in northern Tibet and yields zircon laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) U–Pb ages of 502–492 Ma, providing insight into the possible existence of basement rocks within the South Qiangtang terrane. The granitic gneisses are geochemically similar to high-K, calc-alkaline S-type granites, and Hf isotopic analysis of zircons within the gneisses yields negative εHf(t) values (–7.4 to – 1.1) and old zircon Hf model ages (TDMC = 1757–1406 Ma). These granitic gneisses were generated by partial melting of ancient pelitic rocks, and the resulting melts were contaminated by a small amount of mantle-derived material. Combining our new data with previous research, we conclude that these Cambrian granitic gneisses developed in a post-collisional tectonic setting after Pan-African tectonism. This suggests that the South Qiangtang terrane might have the same early Palaeozoic crystalline basement as the Lhasa, Himalaya, Baoshan, Gongshan, and Tengchong terranes.