东亚原特提斯洋(Ⅰ):南北边界和俯冲极性

ProtoTehtys Ocean in East Asia(Ⅰ) : Northern and southern border faults and subduction polarity

原特提斯洋是从新元古代Rodinia裂解到早古生代发育于滇缅泰/保山微陆块以北、塔里木-华北陆块以南的一个复杂成因的洋盆。长期以来对原特提斯洋的南、北边界及其早古生代末俯冲极性还存在争论,而这是恢复重建Pangea超大陆聚合前构造背景的关键。本文综合利用野外地质、构造、岩浆、沉积学、地球化学、构造年代学和层析成像等最新成果,以期界定原特提斯域的南、北边界位置,确定原特提斯洋边界俯冲极性。集成分析结果表明,北界为古洛南-栾川缝合线(或宽坪缝合线)及其直至西昆仑的西延部分;南界为龙木措-双湖-昌宁-孟连缝合线。原特提斯洋北部在华北-阿拉善-塔里木陆块泥盆纪向南俯冲并与冈瓦纳大陆北缘拼合过程中,形成了一个巨型弯山构造,现保存在祁连-阿尔金-柴达木地区的中国中央造山带内。原特提斯洋南部分支也可能在泥盆纪闭合,使得包括羌北、若尔盖、扬子、华夏、布列亚-佳木斯等在内的大华南陆块、印支陆块等也向南俯冲与冈瓦纳北缘发生了聚合。

The Proto-Tethys Ocean is a complicately-originated oceanic basin originated from Supercontinent Rodinia breakup and existed from Neoproterozoic to the end of the Early Paleozoic. It was located in the range of north of the Yunnan-Burma-Thailand/ Baoshan （Sibumasu） micro-continental blocks and south of the Tarim-North China Block. There is still controversy for a long time on the southern and northern border faults and the late Early Paleozoic subduction polarity of the Proto-Tethys Ocean. It is important for understanding tectonic background, restoration and reconstruction of Supercontinent Pangea assembly. Therefore, this paper used the integrated methods for the latest results of field geology, tectonics, magmatism, sedimentology, geochemistry and tectonic chronology and tomographic imaging, to identify the positions of the southern and northern border faults of the Proto-Tethyan Tectonic Domain, and determine the subduction polarity of the Proto-Tethys Ocean. Integrated analysis results show that to the north is bounded by the paleo- Lnonan-Luanchuan Suture （or Kuanping Suture） and its extension to West Kunlun; the southern boundary is the Longmu Co- Shuaughu-Changning-Menglian Suture. The Tarim-Alax-North China Block in the north of the Proto-Tethys Ocean had a southward subduction polarity and collided with the Gondwana along the northern margin of the Gondwana in the Early Devonian, forming a giant orocline now preserved in the Qilian-Altyn Tagh-Qaidam segment of the Central China Orogen. The south branch of the Proto-Tethys Ocean may be closed, making the Greater South China Block including the North Qiangtang, Ruoergai, Yangtze and Cathaysia, Bureya-Jiamusi and Indochina blocks a southward subduction and accretion to the northern margin of the Gondwana in Devonian.