Early Cretaceous arc granitoids from the central Lhasa subterrane: Production of the northward subduction of Yarlung Zangbo Neo-Tethyan Ocean?
Early Cretaceous arc granitoids from the central Lhasa subterrane: Production of the northward subduction of Yarlung Zangbo Neo-Tethyan Ocean?
复制标题
拉萨地体中部的早白垩世弧花岗岩：雅鲁藏布江新特提斯洋向北俯冲的产生？
DOI：
10.1002/gj.3399
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发表时间：
2019
影响因子：
1.8
通讯作者：
Yu Sheng rui
中科院分区：
文献类型：
--
作者：
Zheng Hao;Huang Qiang Tai;Cai Zhou Rong;Zhang Kai Jun;Liu Hui Chuan;Cheng Chen;Lu Li Juang;Yang Peng;Yu Sheng rui
关于拉萨地体在中生代的成因一直存在争议（羊陆-西藏特提斯洋[YZTO]向北俯冲或班公湖-怒江特提斯洋[BNTO]向南俯冲）。本文报道了阿扎勒花岗岩类的年代学、地球化学和Sr-Nd-Hf同位素数据，以阐明中央次陆壳的主导地球动力学过程。锆石LA-ICP-MS法测得其年龄分别为142.2 ± 1.0和136.6 ± 0.6Ma，表明这些岩石为同生岩石。原位锆石Hf同位素分析得出εHf（t）值为−4.2至−0.1。地球化学上，这些样品大多属于钙碱性系列，并显示出强烈富集大离子亲石元素（LILE;例如，Rb、Ba和Th）和高场强元素（HFSE;例如，Nb和Ta），表明阿扎勒花岗岩类是典型的I型花岗岩。在同位素组成方面，这些岩石也有较低的εNd（t）值（−6.51至−6.80）和较高的初始87 Sr/86 Sr比值（0.7078至0.7084），相对于来自古镁铁质下地壳部分熔融的熔体。我们认为，这些岩石应解释为俯冲带以上的熔融，同化，储存和均质化（MASH过程）的结果。综合前人的研究成果和我们的新资料，我们认为早白垩世弧相关花岗岩类的成因是由于YZTO岩石圈向北俯冲到拉萨地体之下所致。
There is ongoing debate as to the genesis of the Lhasa Terrane during the Mesozoic (northward subduction of Yanglu‐Zangbo Tethyan Ocean [YZTO] or southward subduction of Bangong–Nujiang Tethyan Ocean [BNTO]). In this paper, we report a dataset of geochronology, geochemistry, and Sr–Nd–Hf isotopes for the Azhale granitoids in order to elucidate the dominant geodynamic processes of the central subterrane. These rocks are dated at 142.2 ± 1.0 and 136.6 ± 0.6 Ma by zircon LA–ICP–MS method, indicating that these rocks were contemporaneous. In situ zircon Hf isotopic analyses yielded εHf(t) values of −4.2 to −0.1. Geochemically, these samples mostly belong to calc‐alkaline series and show strong enrichments in large‐ion lithophile elements (LILE;e.g., Rb, Ba, and Th) and depletions in high‐field‐strength elements (HFSE;e.g., Nb and Ta), indicating the Azhale granitoids are typically I‐type granite. In terms of isotopic composition, these rocks also have low εNd(t) values (−6.51 to −6.80) and high initial87Sr/86Sr ratios (0.7078 to 0.7084) relative to melts derived from partial melting of ancient mafic lower crust. We considered that these rocks should be interpreted to have resulted from melting, assimilation, storage, and homogenization (MASH process) above subduction zones. In conclusion, combined with the published and our new data, we argued for the petrogenesis of Early Cretaceous arc‐related granitoids were due to the YZTO lithosphere subducted northward beneath the Lhasa Terrane.