Early Cretaceous bimodal magmatism in the eastern Tethyan Himalayas, Tibet: indicative of records on precursory continental rifting and initial breakup of eastern Gondwana
Early Cretaceous bimodal magmatism in the eastern Tethyan Himalayas, Tibet: indicative of records on precursory continental rifting and initial breakup of eastern Gondwana
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西藏特提斯喜马拉雅山脉东部早白垩世双峰式岩浆作用：表明前兆大陆裂谷和东部冈瓦纳大陆初始裂解的记录
DOI：
10.1016/j.lithos.2018.12.001
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发表时间：
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期刊：
影响因子：
3.5
通讯作者：
Shufeng Yang
中科院分区：
文献类型：
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作者：
Yihong Tian;Junfeng Gong;Hanlin Chen;Lishuang Guo;Qinqin Xu;Lin Chen;Xiubin Lin;Xiaogan Cheng;Rong Yang;Lei Zhao;Shufeng Yang
在这项研究中，我们报告了一个双峰式的辉长岩-花岗质岩套在东特提斯喜马拉雅的措纳地区，这是与大印度和西澳大利亚之间的裂谷事件在冈瓦纳东部。通过全岩常量、微量元素、SHRIMP锆石U-Pb年代学和Hf同位素分析，揭示了双峰套的岩石成因，并探讨了其构造意义。我们的主要发现包括以下几点。首先，辉长岩和花岗岩同时侵位于142-137 Ma，考虑到它们之间的场关系，它们构成了一个双峰套。辉长岩的εHf（t）值为+0.04 ~+8.30，轻稀土元素富集，重稀土元素亏损，Eu异常轻微，总体上反映了辉长岩的洋岛玄武岩地幔源区特征;低MgO、CaO、Al_2O_3，轻稀土元素明显富集，重稀土元素折射率高，Eu负异常强烈，εHf（t）值为-2.01 ~+1.71，具有A_1型花岗岩的特征。根据这些观察，我们认为双峰岩套形成于大陆裂谷。辉长岩起源于地幔柱，而花岗岩则起源于上地壳含石榴子石的变岩。这一裂谷事件开始于140 Ma，这对冈瓦纳东部的最初分裂，特别是大印度与西澳大利亚的分离产生了影响。
In this study, we report a bimodal magmatic suite of gabbroic-granitic rocks in the Cuona area of the eastern Tethyan Himalayas, which is related to the rifting event between Greater India and western Australia in eastern Gondwana. Whole-rock major and trace elements, SHRIMP zircon U-Pb geochronology and Hf isotopic analysis were conducted to reveal the petrogenesis of the bimodal suite and through this to explore the tectonic implications. Our main findings include the following. First, the gabbros and granites were emplaced synchronously at 142-137 Ma, considering the field relationships they comprise a bimodal suite. Second, the gabbros are enriched in light rare-earth-elements (LREE), depleted in heavy rare-earth-elements (HREE) with slight Eu anomalies, and have εHf(t) values of +0.04 - +8.30, which as a whole, suggests that they were derived from an ocean island basalt (OIB)-like mantle source. Third, the granites display low MgO, CaO, and Al2O3, marked enrichment in LREE, highly refracted HREE with strongly negative Eu anomalies and εHf(t) values of -2.01 to +1.71, all of which ultimately gives the characteristics of A1-type granites. Based on these observations, we propose that the bimodal suite is formed in a continental rift. Specifically, the gabbros originated from the mantle plume, whereas the granites derived from the upper crust with garnet-bearing metapelite. This rifting event initiated at 140 Ma, which places bounds on the initial breakup of eastern Gondwana, specifically the separation of Greater India from western Australia.