Zircon U‐Pb Geochronology and Hf Isotopic Constraints on Petrogenesis of Plagiogranite from the Cuomuqu Ophiolite, Bangong Lake Area, North Tibet
Zircon U‐Pb Geochronology and Hf Isotopic Constraints on Petrogenesis of Plagiogranite from the Cuomuqu Ophiolite, Bangong Lake Area, North Tibet
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DOI：
10.1111/1755-6724.12439
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发表时间：
2015-04
期刊：
影响因子：
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通讯作者：
Yin Zhengxin;Yuan Yajuan;Lü Baofeng;Cai Zhourong;Zheng Hao;Huang Qiang-tai;X. Bin;Zhong Yun
中科院分区：
文献类型：
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作者：
Yin Zhengxin;Yuan Yajuan;Lü Baofeng;Cai Zhourong;Zheng Hao;Huang Qiang-tai;X. Bin;Zhong Yun
现场观测、地球化学特征和锆石Hf同位素数据表明，班公湖地区错木曲蛇绿岩形成于超俯冲带（SSZ）上方的弧后盆地（BAB）。对措木曲地块辉绿岩进行锆石U-Pb测年，年龄为164.3±1.9 Ma，表明蛇绿岩杂岩形成于中侏罗世成熟的班公湖-怒江洋弧后伸展期间。斜长花岗岩的锆石εHf(t)和TDMC值分别与辉绿岩的εHf(t)和TDM相似。斜长花岗岩的赋存方式及其块岩和铪同位素特征表明，它们源自地幔，与周围的辉长岩和辉绿岩伴生，是由洋壳横向漂移过程中的蚀变和水合基性岩在剪切条件下部分熔融形成的。斜长花岗岩的锆石U-Pb年龄为156.4±1.4 Ma，比赋存辉绿岩小7.9 Ma。在本研究中，对锆石年代学和 Hf 同位素数据进行了初步分析，以确定错木曲蛇绿岩杂岩中斜长花岗岩的成因。
Field observation, geochemical signatures and zircon Hf isotope data indicate that Cuomuqu ophiolite in the Bangonghu area was formed in a back‐arc basin (BAB) above a supra‐subduction zone (SSZ). Zircon U‐Pb dating of the diabase from the Cuomuqu massif yielded an age of 164.3±1.9 Ma, thus indicating that the ophiolite complex was formed in the Middle Jurassic during back‐arc extension of the mature Bangonghu‐Nujiang Ocean. The zircon εHf(t) and TDMC values of the plagiogranite are similar to the εHf(t) and TDM of the diabase, respectively. The mode of occurrence of plagiogranites and their bulk‐rock and Hf isotope characteristics indicate that they were derived from the mantle, associated with the surrounding gabbro and diabase, and were formed by partial melting of altered and hydrated mafic rocks under shear conditions during lateral drifting of the oceanic crust. The zircon U‐Pb age of the plagiogranite is 156.4±1.4 Ma, and it is 7.9 Ma younger than the hosting diabase. In this study, zircon chronological and Hf isotopic data were tentatively analyzed to determine the genesis of plagiogranites in the Cuomuqu ophiolite complex.