吉林省敦化市松江河金(钼)矿床辉钼矿Re-Os年龄及其地质意义

The molybdenite Re-Os isotopic ages of the Songjianghe gold-(molybdenum)deposit in Dunhua City,Jilin Province and its geological significance

松江河金(钼)矿是近十年来发现的产在韧性变形带内的一座中型金矿床(Au资源储量达9 t)。近年来,在松江河矿区五中段至八中段发现大量辉钼矿分布,至少延深至九中段,从五中至八中段钼矿化具有明显的增强趋势。为确定钼成矿时代,文章利用高精度ICP-MS辉钼矿Re-Os同位素测年技术,首次获得了松江河矿床的辉钼矿Re-Os同位素加权平均模式年龄和等时线年龄分别为(167±2.4) Ma和(158±10)Ma,该年龄与前人报道的松江河矿区黄泥河岩体的年龄(164~162 Ma)和五道溜河岩体的年龄(174~172 Ma)误差范围内基本一致,证实了该矿床成矿与成岩作用近于同时发生,且主要在燕山早期的中、晚侏罗世。结合吉林省中东部地区已发表的成岩与成矿年代学资料,文章认为,区内钼多金属矿床形成于燕山期古太平洋板块向欧亚大陆岩石圈俯冲的活动大陆边缘的地球动力学背景。矿床中辉钼矿的ω(Re)为142.74×10^(-6)~217.67×10^(-6),均值为196.58×10^(-6),结合矿床地质特征和成矿岩体及矿石O、S、Pb同位素等证据,文章认为该矿床的成矿物质主要为地幔来源,来自深部的流体可能对该矿床的成矿作用起了重要作用。

The Songjianghe gold(molybdenum)deposit is a medium-sized gold deposit(with Au reserve of 9 t)discovered in the ductile deformation zone in the past decade.In recent years,a lot of molybdenite has been found in orebodies from fifth to eighth levels and even to the ninth level of the Songjianghe deposit,with an increasing tendency of the molybdenum mineralization from the fifth to the eighth levels.In order to determine the age of molybdenum mineralization,in this paper,the high-precision ICP-MS molybdenite Re-Os isotope dating technology was used to have firstly obtained the weighted average Re-Os isotopic model age of 167±2.4 Ma and the isochron age of 158±10 Ma for molybdenites in the Songjianghe deposit,respectively.These ages are basically consistent with ages(164-162 Ma)of the Huangnihe intrusion and ages(174-172 Ma)of the Wudaotaohe intrusion in the Songjianghe area reported by previous researchers within their standard deviation ranges.It is confirmed that the mineralization of the deposit and the diagenesis of those intrusions occurred almost simultaneously and mainly in the early Yanshanian stage of Middle and Late Jurassic periods.Combined with published chronological data of diagenetic and metallogenic events in the central and eastern regions of Jilin Province,it is believed that many molybdenum polymetallic deposits in the region were formed in the active continental margin geodynamic background by the subduction of the Paleo-Pacific plate toward the Eurasian lithosphere during the Yanshanian movement period.The molybdenites in the deposit haveω(Re)values varying from 142.74×10^(-6) to 217.67×10^(-6),with an average value of 196.58×10^(-6).Combined with geological characteristics of the deposit,O-S-Pb isotopic data of ore-bearing intrusions and ores,it is believed that the ore-forming materials of the deposit were mainly sourced from the mantle and the deeply sourced ore-forming fluids could have played important role for the mineralization of the deposit.