Closure Time of the Junggar‐Balkhash Ocean: Constraints From Late Paleozoic Volcano‐Sedimentary Sequences in the Barleik Mountains, West Junggar, NW China
Closure Time of the Junggar‐Balkhash Ocean: Constraints From Late Paleozoic Volcano‐Sedimentary Sequences in the Barleik Mountains, West Junggar, NW China
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DOI：
10.1002/2017tc004606
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发表时间：
2017-12
期刊：
影响因子：
4.2
通讯作者：
Bo Liu;Bao-Fu Han;Jia‐fu Chen;Rong Ren;Bo Zheng;Zeng-Zhen Wang;L. Feng
中科院分区：
文献类型：
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作者：
Bo Liu;Bao-Fu Han;Jia‐fu Chen;Rong Ren;Bo Zheng;Zeng-Zhen Wang;L. Feng
准噶尔-巴尔喀什洋是古亚洲南洋的一个重要分支。它的关闭时间对于了解中亚造山带的历史很重要。中国西准噶尔巴列克山晚古生代火山沉积序列的沉积学和年代学新资料有助于确定准噶尔-巴尔喀什洋的闭合时间。铁列克提组(FM)以滨海沉积为主，但其上部含海绿石砂岩被解释为在浅水陆架环境下快速沉积。相比之下，黑山头组主要由火山岩组成，与铁列克提组整合覆盖或处于断层接触状态。磨老坝组为平行层状细砂岩和砂砾岩，层理呈渐变状，为典型的陆相河流沉积。该组不整合地覆盖在铁列克提组和黑山头组之上，并被以大陆双峰式火山组合为特征的卡拉岗组整合覆盖。砂岩碎屑锆石的U-Pb年龄和火山岩的锆石U-Pb年龄表明，铁列克提、黑山头、莫拉巴组和卡拉岗组分别沉积于法门期-图尔奈期、图尔奈期-巴什基里期、盖赫期和阿赛尔期-萨克马期。上巴什基里统至卡西莫文的缺失可能是由于西准噶尔地体的构造抬升造成的。这与西准噶尔及邻区出现的同时代缝合岩体是一致的。准噶尔-巴尔喀什洋最终应在吉赫勒洋之前闭合，稍晚于或与古亚洲大洋南部其他洋域同时闭合。
The Junggar‐Balkhash Ocean was a major branch of the southern Paleo‐Asian Ocean. The timing of its closure is important for understanding the history of the Central Asian Orogenic Belt. New sedimentological and geochronological data from the Late Paleozoic volcano‐sedimentary sequences in the Barleik Mountains of West Junggar, NW China, help to constrain the closure time of the Junggar‐Balkhash Ocean. Tielieketi Formation (Fm) is dominated by littoral sediments, but its upper glauconite‐bearing sandstone is interpreted to deposit rapidly in a shallow‐water shelf setting. By contrast, Heishantou Fm consists chiefly of volcanic rocks, conformably overlying or in fault contact with Tielieketi Fm. Molaoba Fm is composed of parallel‐stratified fine sandstone and sandy conglomerate with graded bedding, typical of nonmarine, fluvial deposition. This formation unconformably overlies the Tielieketi and Heishantou formations and is conformably covered by Kalagang Fm characterized by a continental bimodal volcanic association. The youngest U‐Pb ages of detrital zircons from sandstones and zircon U‐Pb ages from volcanic rocks suggest that the Tielieketi, Heishantou, Molaoba, and Kalagang formations were deposited during the Famennian‐Tournaisian, Tournaisian‐early Bashkirian, Gzhelian, and Asselian‐Sakmarian, respectively. The absence of upper Bashkirian to Kasimovian was likely caused by tectonic uplifting of the West Junggar terrane. This is compatible with the occurrence of coeval stitching plutons in the West Junggar and adjacent areas. The Junggar‐Balkhash Ocean should be finally closed before the Gzhelian, slightly later or concurrent with that of other ocean domains of the southern Paleo‐Asian Ocean.