西藏班公湖-怒江缝合带北缘多龙矿集区晚三叠世—侏罗纪增生杂岩结构及其对成矿地质背景的约束

The formation and its geologic significance of Late Triassic-Jurassic accretionary complexes and constraints on metallogenic and geological settings in Duolong porphyry copper gold ore concentration area,northern Bangong Co-Nujiang suture zone,Tibet

西藏班公湖-怒江缝合带北缘多龙斑岩铜金矿集区出露的晚三叠世—侏罗纪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。基质为晚三叠世—侏罗纪砂泥质复理石建造,块体由大小不等的玄武岩、安山玄武岩、灰岩、砂岩、硅质岩、辉长岩、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、剪切面理或韧性剪切断层分隔,为典型造山带大陆增生边缘的增生杂岩。多龙斑岩铜矿的含矿斑岩体侵位于侏罗纪增生杂岩系或以侏罗纪增生杂岩系为基底的岛弧型火山岩系中,属增生楔基础上发育的具有超大型潜力的岛弧型斑岩铜金矿床,其外围的拿若、色拉、拿顿、地保那木岗、鹫山、铁格龙和尕尔勤等系列铜金铅锌矿床点,在空间上均赋存于早白垩世花岗闪长斑岩体内部及其与侏罗纪增生杂岩系的内外接触带中,受矿集区北东向走滑断裂的控制,呈北东向成群展布,二者具有相似的成矿环境与成矿条件,其深部可能存在统一的斑岩型铜金铅锌矿床,属于统一的斑岩浅成低温热液成矿系统。班公湖-怒江缝合带北缘多龙矿集区晚三叠世—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缝合带的演化提供了新的线索。

The outcropped Late Triassic-Jurassic accretionary complexes in Duolong porphyry copper gold ore concentration area of northern Bangong Co-Nujiang suture zone belong to Non-Smith Strata which are totally disordered but partially ordered while ac- cretionary complexes consist of bases and blocks. The bases are Late Triassic-Jurassic sand-muddy flysch formation and blocks consist of basalt, andesite-basalt, limestone, sandstone, silicalite, gabbro and ultrabasic rocks. The accretionary complexes experienced strong tectonic replacement while the bases and blocks were separated by penetrative and unequal extrusion foliations or sheafing foliations, suggesting accretionary complexes of a typical orogenic belt. Researches show that the accretionary complexes were derived from the lateral accretion of Late Triassic-Jurassic southern Qiangtang massif, which was related to the subduction from Meso-Tethys Bangong Co-Nujiang oceanic crust to Qiangtang massif. Porphyry ore in Duolong intruded into accretionary complexes or island arc volcanic rocks based on accretionary complexes. Duolong porphyry copper gold ore and its peripherals, such as Naruo,Sena, Nadun etc, oc-curred in Early Cretaceous granodiorite porphyry body and its contact zone with accretionary complexes, which constrained by E-W pressure faulted structure and N-E strike-slip fault .They have the same metallogenic environments and conditions and belong to uni- form porphyry-epithermal system.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.