内蒙古丰镇市泉子沟斑岩钼矿床成岩成矿年代学及其地质意义

Diagenetic and metallogenic ages of Quanzigou porphyry molybdenum deposit in Fengzhen City, Inner Mongolia, and their geological significance

泉子沟斑岩钼矿床位于内蒙古丰镇市,地处华北克拉通北缘内蒙古台隆凉城断隆内。矿区出露一套燕山期花岗质杂岩体——红娘山杂岩体,主要由中粗粒花岗岩、似斑状花岗岩和石英斑岩组成,钼矿体主要赋存于似斑状花岗岩中。文章在详细的野外地质调查基础上,对泉子沟矿床的成岩成矿时代进行了详细研究,并探讨了地质意义。5件辉钼矿样品的Re-Os模式年龄介于(158.8±2.2)Ma^(161.5±2.2)Ma之间,其加权平均值为(159.8±1.0)Ma(MSWD=0.92),等时线年龄为(161.7±3.1)Ma(MSWD=1.40)。红娘山杂岩体LA-ICP-MS锆石U-Pb年龄分别为:中粗粒花岗岩结晶年龄为(173±1)Ma(MSWD=0.88),似斑状花岗岩侵位年龄为(162±1)Ma(MSWD=0.40),石英斑岩结晶年龄为(160±2)Ma(MSWD=1.90)。辉钼矿Re-Os和锆石U-Pb定年结果表明,泉子沟钼矿床形成于晚侏罗世早期,成矿与似斑状花岗岩关系密切。泉子沟钼矿床的辉钼矿w(Re)介于16.49×10^(-6)~32.87×10^(-6),暗示成矿物质主要来自下地壳。

The Quanzigou porphyry molybdenum deposit is located in Fengzhen City of Inner Mongolia and belongs to the Liangcheng fault-uplift in the Inner Mongolia platform uplift on the northern margin of the North China craton.A Yanshanian granitic complex,namely Hongniangshan complex,is exposed in the deposit,which is mainly composed of medium-coarse grained granite,porphyritic granite and quartz porphyry.The molybdenum orebodies occur mainly in the porphyritic granite.Based on detailed field geological survey,the authors studied the diagenetic and metallogenic ages of the Quanzigou deposit and discussed their geological significance.Five molybdenite samples in the Quanzigou deposit were selected for Re-Os dating,which yielded an isochron age of(161.7±3.1)Ma(MSWD=1.4)and a weighted mean age of(159.8±1.0)Ma(MSWD=0.92).The LA-ICP-MS zircon U-Pb ages of the Hongnianshan complex indicate that the age of medium-coarse grained granite is(173±1)Ma(MSWD=0.88),that of porphyritic granite is(162±1)Ma(MSWD=0.40),and that of quartz porphyry is(160±2)Ma(MSWD=1.90).The results of molybdenite Re-Os and zircon U-Pb dating show that the Quanzigou molybdenum deposit was formed in the early Jurassic and that the mineralization was closely related to porphyritic granite.The w(Re)content of the molybdenite in the Quanzigou Mo deposit ranges from 16.49×10-6 to 32.87×10-6,indicating that the ore-forming materials mainly originated from the lower crust.