帕米尔构造结结构特征与构造演化
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本文为国家自然科学基金资助项目(编号:42172062)和科技部重点研发项目子课题(编号:2021YFC2901904- 1)的成果


Architecture and tectonic evolution of the Pamir Plateau: A review
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    摘要:

    位于印度—欧亚大陆碰撞造山带西段的帕米尔构造结,自震旦纪以来经历了长期的地体裂离、寒武纪至古新世俯冲增生、始新世的最终造山及始新世至全新世大型走滑—伸展、逆冲推覆及构造隆升,记录了最完整的特提斯演化及新特提斯洋关闭后陆内隆升过程。然而,对帕米尔不同地体的构造属性、原特提斯洋俯冲极性、古特提斯阶段是否存在双向俯冲、新特提斯洋俯冲导致的盆山耦合效应以及新生代大规模碱性岩浆活动的地球动力学背景等关键科学问题,仍存在很大争议。笔者等全面总结了前人对帕米尔构造结的研究成果,结合野外地质调查,对帕米尔构造结显生宙以来的构造演化过程做了概括性总结。研究表明,北帕米尔既不是塔里木前寒武纪基底的一部分,也不是三叠纪增生杂岩,它的主体是寒武纪原特提斯洋南向俯冲形成的巨厚增生杂岩(530~500 Ma)。与昆仑—阿尔金不同的是,帕米尔地区的原特提斯洋在早古生代晚期并没有关闭,这一残留洋盆在古特提斯阶段再次扩张,形成了石炭纪—早中生代有限洋盆。随着古特提斯洋的双向俯冲,中、南帕米尔相继与北帕米尔地体发生汇聚,最终拼合的时间在180 Ma左右。古特提斯洋俯冲、关闭伴随着新特提斯洋的打开和扩张,从晚侏罗世开始新特提斯洋沿Shyok缝合带北缘北向低角度或近水平俯冲(开始时间约为160~130 Ma),形成了南帕米尔—喀喇昆仑宽阔的岛弧岩浆岩带,并在中帕米尔及北帕米尔地区,发育与弧后伸展有关的地堑或半地堑沉积及具有板内特征的基性岩浆活动。新特提斯洋最终在始新世关闭(60~50 Ma左右),导致南帕米尔与洋内俯冲形成的科西斯坦—拉达克洋内弧及印度板块的最终拼合,形成了帕米尔雏形。40 Ma左右,由于俯冲板片的拆离,形成这一时期造山后碱性岩浆活动。此后,由于印度板块和欧亚板块的大陆岩石圈不断汇聚,帕米尔构造结的岩石圈厚度急剧增加,沿中帕米尔一带,可能是印度板块与欧亚板块岩石圈地幔的分界,近水平的相向俯冲导致了加厚岩石圈的拆沉,形成沿中帕米尔分布的巨量新生代碱性岩带(25~9 Ma)。

    Abstract:

    The Pamir syntax at the northern margin of the Qinghai—Xizang(Tibet) Plateau underwent a protracted evolution history of terrane drifting, accretion, collision, and final amalgamation of distinct terranes since late Neoproterozoic to early Paleocene. It recorded the whole Tethys evolution process and plays a key role for our undestanding the geodynamics of the Tethys domain. However, some key issues such as the subduction orientation of the Proto- Tethys Ocean, existence or nonexistence of bidirectional subduction of the Paleo- Tethys Ocean and the coupling between northward subdution of the Neo- Tethys Ocean and the basin—mountain architecture, are still hotlly debated. In this contribution, we have compiled the previous data and sketeched its archetecture and Tethys evolution process. Additionally, several key questions related to its tectonic evolution were discussed.Methods: syethesizing the sedimentary sequences, igneous rocks, metmorphic and structural signatures. Results: The Pamir Syntex can be divided into three main tectonic units, i, e, the Northern Pamir, the Central Pamir and the Southern Pamir. Our study demonstrated that the Northern Pamir was neither Precambrian basement nor the Triassic accretionary complex, its main part is the Cambrian accretionary complex induced by the southward subduction of the Proto- Tethys Ocean. Nevertheless, unlike the scenario of the Kunlun—Altyn orogen, the Proto- Tethys Ocean in Pamir had not closed in late Early Paleozoic, this relic ocean reopened in the initial stage of the Paleo- Tethys and the Carboniferous ocean crust within this accretionary complex and coeval rifting- related back- arc volcanic rocks at the southwestern margin of Tarim were fromed. This relic ocean was finally closed during the early Mesozoic as revealed by the Early Jurassic amphibolite- facies metamorphism of the Cambrian accretionary complex. The assumption of the Paleo- Tethys Ocean was accompanied by the opening of the Neo- Tethys Ocean, since the Middle Jurassic, the northward flat subduction of the Neo- Tethys Ocean along the Shyok zone induced the voluminous arc- type igneous rocks in Southern Pamir and at the same time, in the Central and Northern Pamir, back- arc extension basin and minor intraplate- featured igneous rocks were formed. The Neo- Tethys Ocean closed at 60~50 Ma; and at 40 Ma, alkaline volcanic rocks occurred in Kohistan and Central Pamir genetically related to slab delamination were documented. Since 40 Ma, the northward movement of the India Craton led to the quick thickening of the Pamir crust, the delamination of the thickened lithosphere mantle resulted the voluminous alkaline intrusions in the Central Pamir.

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张传林,马华东,刘晓强.2022.帕米尔构造结结构特征与构造演化[J].地质论评,68(5):1653-1673,[DOI].
ZHANG Chuanlin, MA Huadong, LIU Xiaoqiang.2022. Architecture and tectonic evolution of the Pamir Plateau: A review[J]. Geological Review,68(5):1653-1673.

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  • 收稿日期:2022-06-01
  • 最后修改日期:2022-08-10
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  • 在线发布日期: 2022-09-19
  • 出版日期: 2022-09-15