Subduction and accretionary tectonics of the East Kunlun orogen, western segment of the Central China Orogenic System
Subduction and accretionary tectonics of the East Kunlun orogen, western segment of the Central China Orogenic System
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DOI：
10.1016/j.earscirev.2017.12.006
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发表时间：
2018-11-01
影响因子：
12.1
通讯作者：
Li, Jianhua
中科院分区：
文献类型：
--
作者：
Dong, Yunpeng;He, Dengfeng;Li, Jianhua
以阿尔金断裂为界，昆仑造山带可分为东昆仑造山带和西昆仑造山带。E-KOB是华中造山系西段的一部分，被认为是古特提斯洋分支昆仑洋闭合后，柴达木地块与羌塘或巴颜喀拉地体碰撞形成的。根据最近出版的高质量数据汇编，本文概述了E-KOB主要构造要素的组成、性质和年龄，包括蛇绿混杂岩和相关火山岩、侵入岩体和沉积盖层序列。根据这些构造单元的多条证据，提出了一个古生代-三叠纪俯冲-增生构造模式，解释了E-KOB的时空构造格局、板块俯冲极性和增生-碰撞构造过程。东昆仑蛇绿混杂岩带由北向南划分为三个主要的蛇绿混杂岩带，即齐木湖-香日德蛇绿混杂岩带（QXM）、阿其克库勒呼-昆中蛇绿混杂岩带（AKM）和穆塔格-布青山-阿涅马根蛇绿混杂岩带（MBAM）。根据这些蛇绿混杂岩带，将鄂温克盆地划分为四个主要的构造单元：北祁连带、中昆仑带、南昆仑带和巴颜喀拉地体。根据地质学、地球化学和年代学等多方面证据，南昆仑带被解释为与奥陶纪-三叠纪昆仑洋向北俯冲有关的古生代-三叠纪弧前增生杂岩。AKM、MABM和南昆仑带构成了沿着昆仑缝合带的一个广泛的增生杂岩，标志着古特提斯洋的最终闭合，而QXM则代表了另一条缝合带的最佳表现，记录了祁穆弧后盆地的最终闭合。中昆仑带是一个从奥陶纪到三叠纪的长期岛弧构造，在约80年代末，由于祁连弧后盆地的扩张，从柴达木地块裂陷而成。485-425 Ma。综合地质、地球化学和年代学等证据，建立了东昆仑造山带的沟-弧-弧后盆地构造体系，并在古生代-三叠纪演化为沿昆仑缝合带沿着向北的长期俯冲-增生作用。
The Kunlun Orogen is generally divided into the East Kunlun Orogenic Belt (E-KOB) and the West Kunlun Orogenic Belt (W-KOB) by the Altyn Tagh fault. The E-KOB forms part of the western segment of the Central China Orogenic System (CCOS), and is considered to have formed by the collision between the Qaidam Block and Qiangtang or Bayanhar Terrane as a consequence of the closure of the Kunlun Ocean (branch of the Paleo-Tethyan Ocean). Based on a compilation recently published high-quality data, this contribution provides an overview of the composition, nature and ages of the principal tectonic elements, including ophiolitic m langes and related volcanic rocks, intrusive plutons and sedimentary cover sequences in the E-KOB. According to multiple lines of evidence from these tectonic elements, we proposed herewith a Paleozoic-Triassic subduction and accretionary tectonic model to interpret the spatiotemporal tectonic framework, plate subduction polarity, and tectonic processes from accretion to collision of the E-KOB. Three main ophiolitic m lange zones are identified in the E-KOB, from north to south, they are the Qimantagh-Xiangride ophiolitic m lange zone (QXM), the Aqikekulehu-Kunzhong ophiolitic m lange zone (AKM) and the Murtagh-Buqingshan-Anemagen ophiolitic m lange zone (MBAM). According to these ophiolitic m lange zones, the E-KOB is divided into four major tectonic units: the North Qimantagh belt, the Central Kunlun belt, the South Kunlun belt and the Bayanhar Terrane. Based on several lines of evidence from geology, geochemistry and geochronology, the South Kunlun belt is interpreted as a Paleozoic to Triassic fore-arc and accretionary complex related to northward subduction of the Kunlun Ocean during the Ordovician-Triassic time. The AKM, MABM and the South Kunlun belt constitute a wide accretionary complex along the Kunlun Suture zone that marks final closure of the major Paleo-Tethyan Ocean, while the QXM represents the best expression of another suture that records final closure of the Qimantagh back-arc basin. The Central Kunlun Belt, as a long-lived island-arc terrane from Ordovician to Triassic times, rifted from the Qaidam Block due to the spreading of the Qimantagh back-arc basin during the period of ca. 485-425 Ma. Taken into all the geological, geochemical and geochronological lines of evidence together, a trench / arc / back-arc basin tectonic system in the E-KOB was built up, and evolved into a protracted and long-lived northward-subduction and accretion along the Kunlun Suture during Paleozoic and Triassic time.