西藏札达曲松一带两条蛇绿岩带的初步研究

Preliminary Study on Two New Ophiolite Belts in Qusong of Zhada County, Western Tibet

雅鲁藏布江缝合带北支自札达县老武起拉向北西去向不明,南支止于札达县以东。在札达县曲松附近发现了2条蛇绿岩带——夏浦沟蛇绿岩带和波博蛇绿岩带,并在夏浦沟蛇绿岩带台丁拉一天巴拉之间发现了高压变质岩——榴闪岩,对蛇绿岩的空间分析及追索表明它们分别代表雅鲁藏布江缝合带南、北支。其中雅鲁藏布江缝合带南支在札达盆地西北缘首次被发现,而雅鲁藏布江缝合带北支则自老武起拉向西延伸,经研究区内的夏浦沟-台丁拉一带延入印控克什米尔地区,并可能向北西与什约克蛇绿岩相接。由于上述蛇绿岩分别构成北喜马拉雅构造带与札达微陆块、札达微陆块与冈底斯弧之间的板块界线,故它的发现对雅鲁藏布江缝合带西段空间结构的研究及青藏高原大地构造区划的完善具有重要意义。

The track of north branch of Yarlung Zangbo River suture zone extending from Laowuqila to the northwest was uncertain in the past. Recently, two ophiolite belts, Xiapugou ophiolite and Bobo ophiolite are found in Qusong of Zhada County, western Tibet. The high-pressure metamorphic rock is found between Taidingla and Dianbala,northwestern part of the Xiapugou ophiolite too, by 1.250 000 regional geological survey. It is verified that the two opiolites represent the north and south branches of Yarlung Zangbo River suture zone by tracing and anlyses of space. Among them, the south branch of Yarlung Zangbo River suture is found in the northwest edge of Zhada basin for the first time, while the north branch goes through Laowuqila to Taidingla in the study area,then to Keshimir now controled by India, which may link the Shiyueke ophiolite in the northwest. Since the two ophiolites are borderlines among Himalayas, tiny Zhada block, Gangdise arc, this discovery is important to the space framework research of Yarlung Zangbo suture zone and the consummatinn of tectonic division of Tibet plateaus.