内蒙古黄岗夕卡岩型锡铁矿床辉钼矿Re-Os年龄及其地质意义

Molybdenite Re-Os ages of Huanggang skarn Sn-Fe deposit and their geological significance,Inner Mongolia

内蒙古黄岗大型夕卡岩型锡铁矿床位于大兴安岭南段黄岗梁-乌兰浩特锡铅锌铜多金属成矿带。本文利用辉钼矿Re-Os同位素定年方法对黄岗夕卡岩型矿体中5件辉钼矿样品进行了成矿年代测定,获得辉钼矿Re-Os模式年龄为134.6±2.0～136.5±1.9Ma,加权平均年龄为135.31±0.85Ma。辉钼矿Re含量高,显示有地幔物质体参与了成矿过程。大兴安岭地区成矿作用以中生代燕山期成矿为主,存在140～130Ma左右、180～160Ma左右的两次成矿爆发期,其中140～130Ma左右主要出现在岩石圈伸展减薄背景下,与燕山晚期侵入的小岩体有关的锡铅锌铜银多金属矿床;180～160Ma左右主要出现与燕山早期西伯利亚与华北板块后碰撞造山有关的钼铅锌铜金多金属矿床。黄岗锡铁矿床是在古太平洋板块俯冲大陆边缘弧后伸展环境下,发生的大规模成矿作用的产物。

Huanggang large tin-iron skarn deposit,Inner Mongolia,is located in the Huanggangliang-Ulanhot tin-lead-zinc-copper polymetallic belt,South Daxinganling. In this paper,five molybdenite samples separated from the Huanggang skarn ore bodies are used for Re-Os dating and obtained the model ages ranging from 134.6±2.0 to 136.5±1.9Ma,averaging 135.31±0.85Ma. High Re content of molybdenite indicates that mantle fluid is involved in mineralization process. The mineralization of the Da Hinggan Mts area is mainly in Mesozoic Yanshanian,there are two ore-forming eruptive periods,i.e.,ca.140~130Ma and 180~160Ma,while the tin-lead-zinc-copper-silver polymetallic deposits related with the small intrusion in Yanshanian under lithospheric extensional and thinning environment mainly occurred in ca.140~130Ma; the molybdenum-lead-zinc-copper-aurum polymetallic deposits related with the post-collision orogeny of Siberia plate and North China plate in Early Yanshanian mainly occurred in ca.180~160Ma. Huanggang tin-iron deposit is the product of large-scale mineralization under the paleo-Pacific plate subduction environment.