Rifting of the Indian passive continental margin: Insights from the Langjiexue basalts in the central Tethyan Himalaya, southern Tibet
Rifting of the Indian passive continental margin: Insights from the Langjiexue basalts in the central Tethyan Himalaya, southern Tibet
复制标题
印度被动大陆边缘的裂谷：藏南特提斯喜马拉雅中部朗杰雪玄武岩的见解
DOI：
10.1130/b36204.1
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发表时间：
2022
期刊：
影响因子：
--
通讯作者：
Yue Yahui
中科院分区：
文献类型：
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作者：
Wang Chao;Ding Lin;Cai Fulong;Zhang Liyun;Li Zhenyu;Yue Yahui
藏南特提斯喜马拉雅三叠纪构造环境一直存在争议，是揭示新特提斯洋开启机制和冈瓦纳大陆裂解历史的关键。本文报道了藏南特提斯喜马拉雅序列中227 - 225 Ma的基性火山岩，它们形成于典型的被动大陆边缘环境。玄武岩为拉斑玄武岩，具有高TiO 2（3.20 - 3.38 wt%）和中等MgO（4.05 - 5.40 wt%）含量，并显示出富集轻稀土元素和弱的负Nb、Ta、Eu和Ti异常。这些地球化学成分，再加上均匀的全岩εNd（t）（+1.50至+2.70）值，表明岩浆是由深层石榴子石源的低度熔融产生的，该源被大洋岛屿玄武岩非均质改性。类型的成分。结合其他地质证据，我们认为特提斯喜马拉雅地区晚古生代-中生代岩浆演化总体上是一个岩石圈减薄过程，即从晚二叠世的大陆裂谷系统发展到三叠纪的岩浆活动减弱。这一解释进一步支持了新特提斯洋以被动方式打开以及冈瓦纳大陆在晚古生代的裂解是由岩石圈减薄引发的假说。因此，随后的岩浆活动与正常软流圈物质的被动上涌有关。
The Triassic tectonic setting of the Tethyan Himalaya in southern Tibet remains controversial and is key to revealing the mechanism of Neo-Tethys Ocean opening and the breakup history of Gondwana. This paper reports 227−225 Ma mafic volcanic rocks interbedded within the Tethyan Himalaya sequence in southern Tibet, which were formed in a typical passive continental margin setting. The basalts are tholeiitic with high TiO2 (3.20−3.38 wt%) and moderate MgO (4.05−5.40 wt%) contents and exhibit enrichment in light rare earth elements and weak negative Nb, Ta, Eu, and Ti anomalies. These geochemical compositions, combined with uniform whole-rock εNd(t) (+1.50 to +2.70) values, indicate that the magmas were derived by low-degree melting of a deep-seated garnet source that was heterogeneously modified by an oceanic island basalt-type of component. Given the other geological evidence, we propose that the magmatic evolution of the Tethyan Himalaya during the late Paleozoic−Mesozoic was generally a lithospheric thinning process, that is, it evolved from a fully developed continental rift system during the Late Permian to wane during the Triassic. This interpretation further supports the hypothesis that the Neo-Tethys Ocean opened in a passive pattern and that the breakup of Gondwana in the late Paleozoic was initiated by lithospheric thinning. Therefore, the subsequent magmatism was related to the passive upwelling of normal asthenospheric materials.