摘要
基于对中国西南特提斯巨型造山系的时空结构和构造－岩浆事件分析研究提出．泥盆－石炭纪时期出现于昌都－思茅陆块两侧的热幔柱导致了金沙江洋和澜沧江洋成对打开，热幔柱岩浆作用沿洋脊产出苦橄玄武岩和洋岛玄武岩，并造成区域地球化学异常。二叠纪末期出现于昌都－思茅－印支中央陆块下的冷幔柱导致了两大洋向该陆块下俯冲消减，陆块两缘发育沟－弧－盆体系，构成冷幔柱的洋壳板片在２００Ｍａ时期堆积沉落，诱发板块后继俯冲，产生滞后型孤火山－岩浆岩。发育于冈瓦纳大陆北缘的德干热幔柱在株罗纪导致怒江洋和雅鲁藏布江洋相继打开，在白垩纪末期（６６Ｍａ）形成德干玄武岩省。发育于劳亚大陆南缘的峨眉热幔柱在二叠纪，导致峨眉火成岩省的形成，在早中三叠世使甘孜－理塘断裂带扩张成洋。冷幔柱的持续发生，决定了雅鲁藏布江洋和甘孜－理塘向昌都－思茅陆块方向的俯冲消减，以及来自冈瓦纳大陆和劳亚大陆陆块分别向昌都－思茅陆块南北两侧拚贴和碰撞。
our plate suture zones and five diverse blocks bounded by these suture zones have been recognized in the Tethys domain in Sanjiang, China. These suture zones are Ganzi-Litang, Jinshajiang-Ailaoshan, Lancangjiang and Yarlung Zangbo suture zones, while the blocks are Zhongza,Qamdo-Simao, Baoshan(Qiangtang)and Lhasa blocks, cross the Tethyan Region in S. W. China. The relics ophiolites, ophiolitic melanges, abyssal sediments and high-pressure metamorphic rocks developed along these suture zones. Volcano arc or/and magma arc usually coupled with suture zone, and constitute trench-arc-basin system. The new geological data in the paper indicate that paleo-Tethys Ocean opened in Devout an-Carboniferous period to form the Lancangjiang and Jinshajiang-Ailaoshan oceanic branches in both sides of Qamdo-Simao central continent, located between Gondwana and Lauasian Lands. The two ocean slabs became to subduct forward underneath Qamdo-Simao continent (block) since Late Permian, and resulted in formation of Tuobajinghong arc-basin system and Jiangda-Luchun arc-basin system developed along southern and northern margins of the central continent, respectively. Corresponding to the subductions and closure of the two oceanic branches, the meso-Tethys became to deveolp since Triassic period. the Ganzi-Litang oceanic basin opened during Late Permian-Late Triassic, and resulted in drifting of the Zhongza block from Yangtze continent. The Yarlung Zangbo ocean and Nujiang oceanic basin opened at the end of Late Triassic and the Lhasa and Qiangtang bolcks left from northern margin of Gondwana Land. Both the Litang and Yarlung Zangbo oceanic slabs subducted forward Qamdo-Simao central continent in Late Triassic and Jurassic-Cretaceous, respectively, corresponding to the closure of both the oceans. The Triassic Yidun island-arc and Gangdise magmatic arc developed in eastern side of the Jinshajiang suture zone and southern side of Lancangjiang suture, respectively.The lithosphere evolution of the Tethys in Southwestern China seems to be complained by the plume tectonics model. The model emphasis that a huge cold plume occurred underneath the Qamdo-Simao central continent since Early Permian and two hot plumes from deeper mantle appeared in northern margin of the Gondwana Land in Late Triassic(Renuion Plume)and southern Inargin of the Yangtze continent in Late Permian(Emei Plume). The Reunion Plume resulted in the development of the Deccan flood basalt probing and breakup of the Seychells block from mainland india in Late Cretaceous(Whit and McKenzie, 1989), and probably supplied a huge driving force for the opening of the Yarlung Zangbo ocean at end of Triassic. The Emei Plume resulted in formation of the Emeishan food basalt province in Late Permian(Lu, 1996) and opening of the Litang ocean in Triassic. The cold plume underneath QalndthSimao central continent occurred in Permian period probably is located in the Vietnam downwelling center (Iodine, 1989), based on available paleo-magnetic data and seismic tomograpy in Southwestern China and dating ages of colliding granites along northeastern side of the Lancangjiang suture zone. The cold plume resulted in Subduction in early paired of two branches of the paleo-Tethys Ocean forward underneath Qamdo-Simao continent and drifting of the blocks from the margins of the Gondwana Land and Yangtze continent to the Qamdo-Simao central continent.
