柴北缘尕秀雅平东和红柳沟北镁铁-超镁铁质岩体锆石U-Pb年龄及其找矿意义

摘要

位于柴达木地块北缘构造带内欧龙布鲁克微陆块东缘的2个镁铁-超镁铁质岩体——含Cu-Ni的尕秀雅平东岩体和含Ti-Fe的红柳沟北岩体,前者的LA-ICP-MS锆石U-Pb年龄为408.0±1.5Ma,属早泥盆世;后者的SHRIMP锆石U-Pb年龄为418.3±2.8Ma,属晚志留世.区域地质资料研究表明,东昆仑地区、柴北缘在晚志留世—晚泥盆世处于后造山伸展阶段,尕秀雅平东岩体和红柳沟北岩体正是拉张环境下幔源岩浆活动的产物.在东昆仑地区、柴北缘发现的铜镍矿床和铜镍矿点(除夏日哈木有争议外)基本都形成于晚志留世—晚泥盆世.结合区域成矿年代学研究,认为晚志留世—晚泥盆世期间,东昆仑造山带和祁连造山带之间的柴达木地块、欧龙布鲁克微陆块,以及位于这两大造山带内部的微型古陆块区,是形成岩浆铜镍硫化物矿床和钛铁氧化物矿床的有利环境.%This paper reports two mafic-ultramafic intrusions in the Oulongbuluck microblock on the northern margin of Qaidam Basin. One is Cu-Ni-bearing Gaxiuyapingdong intrusion with LA-ICP-MS zircon U-Pb age of 408.0±1.5Ma belonging to Early Devonian;the other is Ti-Fe-bearing Hongliugoubei intrusion with SHRIMP zircon U-Pb age of 418.3±2.8Ma belonging to Late Silurian. Regional geological data show that Eastern Kunlun and North Qaidam should be in a post-orogenic extension environ-ment during the Late Silurian-Late Devonian period. Gaxiuyapingdong intrusion and Hongliugoubei intrusion were produced by mantle-derived magmas in an extensional environment. The copper-nickel deposits and ore spots such as Niubiziliang, Binggounan, and Shitoukengde discovered in Eastern Kunlun and North Qaidam (except for Xiarihamu) were all formed in Late Silurian-Late De- vonian period. Combined with regional metallogenic chronology, the authors consider that Qaidam Block as well as Olongbuluck mi-cro-block between Eastern Kunlun orogenic belt and northern margin of Qaidam Basin and micro-ancient continental block be-tween these two orogenic belts were favorable for the formation of magmatic Cu-Ni sulfide and Ti-Fe oxide deposits during Late Silurian-Late Devonian period.