Late Paleozoic tectonic amalgamation of northwestern China: Sedimentary record of the northern Tarim, northwestern Turpan, and southern Junggar Basins
Late Paleozoic tectonic amalgamation of northwestern China: Sedimentary record of the northern Tarim, northwestern Turpan, and southern Junggar Basins
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DOI：
10.1130/0016-7606(1995)107
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发表时间：
1995-05
影响因子：
4.9
通讯作者：
A. Carroll;S. Graham;M. Hendrix;D. Ying;Da Zhou
中科院分区：
文献类型：
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作者：
A. Carroll;S. Graham;M. Hendrix;D. Ying;Da Zhou
田山相邻盆地中的沉积岩为中国西北部晚古生代大陆融合提供了漫长而复杂的记录，补充了该山脉内保存的岩石所提供的记录。这一记录包括沉积相、沉积物扩散模式、砂岩来源和盆地沉降速率的戏剧性变化，广泛支持了前人对田山演化的两部分解释：晚泥盆世至早石炭世塔里木陆块与田山中央的碰撞，随后该组合块体与北部的田山和博格达山在晚石炭世-早二叠世的岛弧碰撞。第一次碰撞导致了塔里木盆地内部广泛的角度不整合。碰撞后的持续汇聚沿着塔里木地块北缘形成了一个长期存在的弯曲前缘，它通过下二叠统河流和来自塔里木内部的海洋沉积物接收了至少2000米的下石炭统。随后塔里木盆地北部早二叠世陆相伸展，形成了互层陆相硅质碎屑沉积岩和镁铁质-长英质火山岩。该段砂岩起源于古田山组，主要由与流纹岩相似的岩屑火山颗粒组成。与塔里木盆地不同，吐鲁番北部和准噶尔盆地西北部石炭系和二叠系沉积以钙碱性火山岩和火山成因沉积岩为主。田山和博格达山北部的火山弧在晚石炭世早期保持活跃，在准噶尔盆地西北部沉积了一公里厚的深部海洋沉积物-重力流。晚石炭世以来，随着塔里木/田山中部地块与北田山/博格达山弧之间洋盆的闭合，主要弧型岩浆活动停止。准噶尔盆地西北部的上石炭统至下二叠统岩石组成了一个海洋深度的等深盆地的沉积充填物(在火山弧的北侧)，最终形成了一个1000米厚的海退层序。中、上二叠统砂岩起源于隆起的古田山期，具有现今出露的花岗岩的独特物源印记。准噶尔盆地晚二叠世的下沉容纳了5千米的陆相沉积；然而，这种下沉的原因及其与区域构造事件的关系仍然存在争议。
Sedimentary rocks contained in basins adjacent to the Tian Shan provide a long and complex record of the late Paleozoic continental amalgamation of northwestern China, complementing that provided by rocks preserved within the range. This record, which comprises dramatic changes in sedimentary facies, sediment dispersal patterns, sandstone provenance, and basin subsidence rates, broadly supports previous interpretations of a two-part evolution of the Tian Shan: Late Devonian to Early Carboniferous collision of the Tarim continental block with the Central Tian Shan, followed by collision of this combined block with island arcs in the north Tian Shan and Bogda Shan in Late Carboniferous–Early Permian times. The first collision resulted in widespread angular unconformities within the Tarim basin. Continued convergence following the collision created a long-lived flexural foredeep along the northern margin of the Tarim block, which received at least 2000 m of Lower Carboniferous through Lower Permian fluvial and marine sediment derived from the interior of Tarim. Subsequent Early Permian continental extension of the northern Tarim basin resulted in the deposition of interbedded nonmarine siliciclastic sedimentary rocks and mafic to felsicvolcanic rocks. Sandstone within this interval was derived from the paleo–Tian Shan, and is composed predominantly of lithic volcanic grains similar to the rhyolite. In contrast to the Tarim basin, calc-alkaline volcanic rocks and volcanogenic sedimentary rocks dominated Carboniferous and Permian sedimentation in the northern Turpan and northwestern Junggar basins. Volcanic arcs remained active in the North Tian Shan and Bogda Shan through the early Late Carboniferous, depositing a kilometers-thick interval of deep marine sediment-gravity flows in the northwestern Junggar basin. Major arc magmatism ceased in the Late Carboniferous in response to closure of the oceanic basin between the combined Tarim/Central Tian Shan block and the North Tian Shan/Bogda Shan arcs. Upper Carboniferous through Lower Permian rocks in the northwestern Junggar basin compose the sedimentary fill of a bathymetric basin of oceanic depth (on the northern side of the volcanic arcs), culminating in a 1000-m-thick marine regressive sequence. Middle to Upper Permian sandstones were derived from the uplifted paleo–Tian Shan and bear the distinctive provenance imprint of granitic rocks presently exposed within the range. Late Permian subsidence of the Junggar basin accommodated >5 km of nonmarine sediments; however, the cause of this subsidence and its relationship to regional tectonic events remain controversial.