吉林通化赤柏松铜镍硫化物矿床Re-Os同位素研究及其地质意义

Re-Os isotope study and its geological significance of chibaisong Cu-Ni sulfide deposit in Tonghua, Jilin Province

赤柏松岩浆型铜镍硫化物矿床位于华北克拉通胶辽吉带,含矿镁铁质—超镁铁质岩侵入到鞍山群最下部的四道砬子河组变质岩中;该矿床硫化物矿样品的Os和Re浓度分别为19×10^(-3)~490×10^(-3)和0.47×10^(-3)~13.97×10^(-3),对这些数据分析得出了一条6点Re-Os等时线年龄为1 885±94 Ma,矿石的初始(187)^Os/(188)^Os 比值为0.80±0.16 (MSWD=0.17),表明矿石为岩浆源,熔体主要由地幔贡献,但在成矿过程及岩浆侵位期间有不少地壳物质混入成岩成矿系统。新的Re-Os年代学结果表明,赤柏松镁铁质—超镁铁质侵入体与铜镍矿床形成于古元古代,而不是前人认为的早白垩世。

The Chibaisong magmatic Cu-Ni sulfide deposit is located in Jiaoliaoji belt of the North China Craton,and ore-bearing mafic and ultramafic intruded into the metamorphic rocks of Sidaolazihe Formation in the lowest part of Anshan Group.The Os and Re concentrations of sulfide ores from the deposit are 19×10^(-3)~490×10^(-3)and 0.47×10^(-3)~13.97×10^(-3),respectively.Analysis of these data yields a six-point Re-Os isochron of 1 885±94 Ma.The initial(187)^Os/(188)^Os ratio of the ores is 0.80±0.16(MSWD=0.17),indicating that the ore is a magmatic source and the melt is mainly contributed by the mantle.However,a lot of crustal materials were mixed into the diagenetic and metallogenic system during the mineralization process and magmatic emplaced.The new Re-Os dating results show that the mafic and ultramafic intrusions and the Cu-Ni deposit occurred in the Paleoproterozoic,rather than the result of post-orogenic extension in the Early Cretaceous as previously thought.