西藏班公湖-怒江结合带北缘多龙地区侏罗纪增生杂岩的特征及意义

Zhang L.The discovery of Jurassic accretionary complexes in Duolong area,northern Bangong Co-Nujiang suture zone,Tibet,and its geologic significance

西藏班公湖-怒江成矿带北部多龙矿集区出露的增生杂岩属总体无序、局部有序的非史密斯地层,由基质和块体2个部分组成。基质为侏罗系砂泥质复理石建造,块体由大小不等的玄武岩、砂岩、硅质岩、泥质灰岩、超基性岩等组成。增生杂岩系变形强烈,发育强烈的构造置换作用,块体与基质之间由透入性挤压面理或剪切面理分隔,为典型造山带大陆增生边缘的增生杂岩。这套增生杂岩形成于侏罗纪羌塘陆块南缘的侧向增生边缘,发育于晚古生代增生杂岩系之上,与班公湖-怒江中特提斯洋壳侏罗纪时期向羌塘陆块的俯冲作用有关,侏罗纪—白垩纪羌多岩浆弧为在这套增生楔基础上发育起来的火山-岩浆弧。班公湖-怒江结合带北缘多龙地区侏罗纪增生杂岩的识别为正确认识多龙超大型斑岩铜金矿床的成矿地质背景和结合带的演化提供了新的线索。

The outcropped accretionary complexes in Duobuza-Bolong ore concentration area of northern Bangong Co-Nujiang metallogenic belt belongs to Non-Smith Strata which are totally disordered but partially ordered and deformed strongly.The bases are Jurassic sand-muddy flysch formation and blocks consisting of basalt,sandstone,silicalite,argillaceous limestone and ultrabasic rocks which differ in size.The accretionary complexes experienced strong tectonic replacement while the bases and blocks were separated by penetrative and unequal extrusion foliations or shearing foliations,suggesting accretionary complexes of a typical orogenic belt.Researches show that the accretionary complexes were derived from the lateral accretion of Jurassic southern Qiangtang massif,which was related to the subduction from Meso-Tethys Bangong Co-Nujiang oceanic crust to Qiangtang massif.Qiangduo magma arc can be described as continental margin volcanic-magmatic arc based on accretionary wedge.This new understanding provides new clues for understanding the geological background of the Duobuza-Bolong superlarge porphyry copper-gold deposit and the evolution of the Bangong Co-Nujiang suture zone.