黑龙江多宝山铜(钼)矿床叠加成矿:辉钼矿Re-Os年龄和硫化物原位硫同位素证据  

Superimposed mineralization of the Duobaoshan Cu(Mo) deposit in Heilongjiang Province:Indicated by the molybdenite Re-Os isotopic dating and sulfur isotope composition

作　　者：索青宇 李昌昊[1,2,3] 申萍 赵俊康[4] 楚翔凯 SUO QingYu;LI ChangHao;SHEN Ping;ZHAO JunKang;CHU XiangKai(Key Laboratory of Mineral Resources,Institute of Geology and Geophysics,Chinese Academy of Sciences,Beijing 100029,China;College of Earth and Planetary Sciences,University of Chinese Academy of Sciences,Beijing 100049,China;Innovation Academy of Earth Science,Chinese Academy of Sciences,Beijing 100029,China;Geological Prospecting Institute,Zijin Mining Group Co.,Ltd.,Xiamen 361000,China)

机构地区：[1]中国科学院地质与地球物理研究所,中国科学院矿产资源研究重点实验室,北京100029 [2]中国科学院大学地球与行星科学学院,北京100049 [3]中国科学院地球科学研究院,北京100029 [4]紫金矿业集团股份有限公司矿产地质勘查院,厦门361000

出　　处：《岩石学报》2023年第11期3479-3490,共12页Acta Petrologica Sinica

基　　金：中国科学院国际合作局国际伙伴计划(132A11KYSB20190070);国家自然科学青年基金项目(42002092);国家重点研发计划项目(2021YFE0190600)联合资助。

摘　　要：斑岩型矿床易受后期岩浆、构造、变质等地质作用影响,使得矿床自身发生改造变形。后期的热事件不仅可以将原有矿体再活化,还能够带来新的成矿物质,进而发生新一期成矿作用。不同地质时期的成矿作用在同一空间互相叠加,会形成与斑岩矿床矿化特征截然不同的矿床,称为叠加改造型斑岩矿床。多宝山铜(钼)矿床位于中亚造山带东段,兴蒙造山带内。该矿床在成矿构造地质、矿石组构和成矿期次等方面表现出多期改造与叠加成矿的特征。本次根据野外观察和成矿年代学研究,推测多宝山铜矿至少存在两期成矿作用。对采自矿坑340平台10件叠加矿化类型的辉钼矿样品进行Re-Os同位素分析,获得辉钼矿的模式年龄介于435.6±10.5Ma~446.1±7.1Ma之间,等时线年龄为440.1±4.5Ma (MSWD=0.56)。结合前人获得的年龄资料,确认多宝山叠加成矿与晚奥陶世玄武安山岩应形成于统一的成岩成矿地质事件。不同矿化期次的黄铜矿和黄铁矿原位硫同位素结果显示:典型斑岩型矿脉中黄铜矿δ^(34)S平均值为-2.12‰;叠加矿化黄铜矿δ^(34)S平均值为-1.78‰,黄铁矿δ^(34)S平均值为-1.03‰,均落入幔源硫范围,表明硫主要来自岩浆。而前人在叠加期形成的黄铜矿中,测试到较低的δ^(34)S值(-12.9‰~-5.6‰),这是后期流体易携带轻硫^(32)S发生迁移并在应力较低的区域内重新沉淀的结果。同位素组成指示叠加成矿期的矿化元素即来源于新的岩浆活动,又继承了先前存在的岩(矿)体。Porphyry copper deposits can be deformed by subsequent magmatic-tectonic-metamorphic evolution,resulting in the consequent superimposed mineralization and the remobilization of pre-existing ores.This process might potentially increase the ore grade and/or resource.We focus on the Duobaoshan Cu(Mo) deposit,two mineralization periods were identified within the Duobaoshan deposit in this study,i.e.,the porphyry period and the superimposed period.Ten molybdenite samples from the superimposed period yield Re-Os isotopic model ages of 435.6±10.5Ma to 446.1±7.1Ma,and an isochron age of 440.1±4.5Ma(MSWD=0.56).Combined with the age of magmatic activity developed in the region,it is suggested that the superimposed mineralization and the Late Ordovician basaltic andesite should be formed in a unified geological event in the Duobaoshan deposit.The in-situ sulfur isotope results of chalcopyrite and pyrite from different mineralization periods show that the average δ^(34)S value of chalcopyrite in typical porphyry veins is-2.12‰,while those of chalcopyrite and pyrite in the superimposed mineralization are-1.78‰ and-1.03‰,respectively,which fall into the range of a mantle source,indicating that the sulfur of the deposit mainly comes from the magma.However,previous studies have found that chalcopyrite formed during the superimposed mineralization has low δ^(34)S values(-12.9‰~-5.6‰) as a result of the migration of light sulfur ^(32)S which is easily carried by late-stage fluids and deposited in areas of a lower stress.The isotopic compositions indicate that the mineralized elements in the superimposed period either originated from new magmatism or inherited from pre-existing rock(ore) bodies.

关 键 词：多宝山斑岩铜(钼)矿床 叠加成矿 铼锇同位素年龄 硫同位素 

分 类 号：P597[天文地球—地球化学] P618.65[天文地球—地质学]