新疆喀拉通克铜镍硫化物矿床Re-Os同位素测年及成矿物质来源示踪

Re-Os dating and ore-forming material tracing of the Karatungk Cu-Ni sulfide deposit in northern Xinjiang

通过对喀拉通克矿区1号和2号岩体中铜镍硫化物矿石的Re_Os同位素测年,获得两个等时线年龄数据分别为282.5±4.8Ma和290.2±6.9Ma,187Os/188Os初始比值分别为0.2563±0.0037和0.2721±0.0053,γOs值分别为202.23～1061.59和195.07～473.24,平均值分别为495.05和289.83。上述结果表明成岩成矿年龄极为接近,均介于石炭纪末至早二叠世之间,并且在成矿和岩浆侵位过程中有大量地壳物质混入成岩成矿系统。喀拉通克镁铁质超镁铁质岩带形成于后碰撞的伸展构造环境。

A series of mafic_ultramafic plutons are distributed in the southern margin of Altay folded belt and many of them are associated in space and time with Cu_Ni sulfide deposits. As geologists are divided in opinion on the genesis of the mafic_altramafic rocks, the genesis of mineralization is still a problem of much controversy. Some chalcopyrite, pyrrhotite and pentlandite samples were collected from the No.1 and No.2 intrusions of the Cu_Ni sulfide ores in the Karatungk deposit to carry out Re_Os dating and tracing of ore_forming materials. The two groups of measured points defined isochronal ages of 282.5±4.8 Ma and 290.2±6.9 Ma with the initial (()^(187)Os)/^(188)Os rates being 0.256?3±0.003?7 and 0.272?1±0.005?3, respectively. The data show that the ore_forming age is later than that of the Early Carboniferous rocks which host the mafic_altramafic intrusions, and is corresponding to the extension stage. They share the same mineralization time with the extensively developed shear zone type gold deposits. The ages are also similar to the alkali_rich granitoids developed in the southern margin of Altay folded zone and the northern margin of the Junggar folded belt. Their initial ()^(187)Os/^(188)Os values and γ_(Os) values of 202.23～1?061.59 and 195.07～473.24 indicate that large quantities of crustal substances were mixed with the Cu_Ni sulfide metallogenic system in the ore_forming process.