西昆仑于田南部苏巴什蛇绿混杂岩的组成、地球化学特征及地质意义

Composition and geochemistry of the Subashi ophiolitic mélange in the West Kunlun and its geological significance

在1∶25万于田县幅区域地质调查中,发现西昆仑苏巴什一带与基性侵入岩、玄武岩紧密共生的“超镁铁质岩石”,为蛇绿岩组合。该蛇绿岩有高的稀土和微量元素丰度,表明其来源于富集地幔。基性杂岩和基性火山岩低Ti、高K,大离子亲石元素(LILF)相对于高强场元素(HFSE)更加富集,以及伴生有大量陆缘碎屑沉积等特征综合说明,蛇绿岩形成于弧后盆地环境,属于SSZ型蛇绿岩。与之伴生的硅质岩中的放射虫化石显示其形成时代早于中二叠世。

During the regional geological survey of the 1∶250000 Yutian County Sheet, the authors found that 'ultramafic rocks' in the Shubashi area, West Kunlun, are intimately associated with basic intrusive rocks and basalt, which combine to form ophiolite. This ophiolite has higher REE and trace element abundances, suggesting it was derived from the enriched mantle. The basic complex and basic volcanic rocks are low-Ti and high-K, large ion lithophile elements (LILF) are enriched relative to high-field strength elements (HFSE) and there occur abundant continental-margin clastic deposits-all these suggest that the ophiolite originated in a back-arc basin, belonging to SSZ type ophiolite. Dating of radiolarians in cherts associated with the ophiolite suggests that its age is earlier than Middle Permian.