Formation of the Permian basalts and implications of geochemical tracing for paleo-tectonic setting and regional tectonic background in the Turpan-Hami and Santanghu basins, Xinjiang
Formation of the Permian basalts and implications of geochemical tracing for paleo-tectonic setting and regional tectonic background in the Turpan-Hami and Santanghu basins, Xinjiang
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DOI：
10.1007/s11430-006-0584-1
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发表时间：
2006
期刊：
影响因子：
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通讯作者：
Ding-wu Zhou;Yiqun Liu;Xiujuan Xing;J. Hao;Yunpeng Dong;Z. Ouyang
中科院分区：
文献类型：
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作者：
Ding-wu Zhou;Yiqun Liu;Xiujuan Xing;J. Hao;Yunpeng Dong;Z. Ouyang
吐哈盆地和三塘湖盆地是叠置在古生代造山带褶皱基底之上的晚古生代-中生代-新生代改造型陆内盆地。从玄武岩的地球化学对比来看，三塘湖玄武岩表现出强烈的Nb、Ta亏损和HFSE选择性富集，反映源区受到与古洋壳俯冲有关的俯冲组分的影响，具有“滞后弧火山岩”的特征。相比之下，吐哈玄武岩的Nb和Ta略有亏损，Th/Ta比值较高，类似于陆内伸展带或初始裂谷中形成的玄武岩。结合新疆北方蛇绿混杂岩带的形成时期和造山后拉张背景下的区域岩浆活动，可以推断出吐哈盆地和三塘湖盆地形成的大地构造背景与陆-陆碰撞造山后的区域拉张作用密切相关。两个盆地的玄武岩来自不同的源区，具有相似的成盆动力学背景和造山后伸展作用。尽管其背景均为陆内裂谷，但三塘湖玄武岩的源区明显受到俯冲组分的交代作用，暗示有前一次俯冲作用的存在。
The Turpan-Hami and Santanghu basins are the late Paleozoic-Mesozoic-Cenozoic reworked intracontinental basins that superposed on the folded basement of the Paleozoic orogenic belt.40Ar/39Ar geochronological study of the basalts developed in the basins reveals that the formation period is Permain (293–266 Ma). From geochemical comparison of the basalts, the Santanghu basalts exhibit a strong depletion in Nb and Ta, and a selective enrichment in HFSE, reflecting that the source region is influenced by the subducted components related to subduction of the ancient oceanic crust and characterized with “lagged arc volcanic rocks”. In contrast, the Turpan-Hami basalts show a slight depletion in Nb and Ta, high Th/Ta ratio, similar to the basalts formed in an intracontinental extensional zone or in an initial rift. Combined with the formation period of the ophiolite and ophiolite mélange zones and regional magmatic activities occurring on the post-orogenic extensional background in northern Xinjiang, it can be inferred from these geochemical characteristics that the tectonic background for forming the Turpan-Hami and Santanghu basins is closely related to the regional extension after the continent-continent collisional orogeny. The basalts of the two basins came from different sources on the post-orogenic extensional background of the similar basin-forming dynamics. Although the settings are all intracontinental rift, the source for the Santanghu basalts is obviously subjected to the metasomatism of the subducted components, implying the existence of the previous subduction.