新疆喀拉通克铜镍硫化物矿床Re-Os同位素研究及其地质意义

Re-Os isotopic analysis of the Kalatongke Cu-Ni Sulfide Deposit,Northern Xinjiang,NW China,and its geological implication.

喀拉通克铜镍硫化物矿石的Re—Os同位素测年结果为305±15（2σ）Ma。该数据表明产于阿尔泰山南缘的铜镍硫化物矿床形成于晚石炭世-早二叠世，与区内广泛发育的造山型金矿和浅成低温热液型金矿基本为同一时期。其等时线^187Os／^188Os初始比值为0．35±0．04，γOs值平均为183，表明在成矿过程及岩浆侵位期间有少量地壳物质加入成矿系统中。

The Kalatongke is a large Cu-Ni deposit in the southern part of the Altay orogenic belt, northwestern China. Rhenium and osmium isotopic analyses of Ni-and Cu-bearing sulfide minerals from the deposit have been used to determine the timing of mineralization, the source of osmium, and, by inference, the source of ore metals. Sulfide ore samples have osmium and rhenium concentrations varying in the ranges of 0.29 - 3.07 ppb, and 6.605 - 61.10ppb, respectively. Analyses of these data yield a six-point isochron with an age of 305 ± 15Ma. The age implies that the Cu-Ni sulfide deposit and other related magmatic deposits in the same area formed between the latest Carboniferous and Early Permian post-collisional extension in the Altay Shan. An initial ^187Os/^188Os ratio of 0. 352 ± 0.044 （ MSWD = 2.1 ） and the δ^34S of - 3.5‰ to ＋ 3.0‰ for the ores, as well as initial ^87Sr/^86Sr ratios of metalliterous intrusions that vary from 0. 70375 to 0. 70504, suggest a magmatic source for the ores, with the melts being dominated by mantle contributions. The data also indicate that the Kalatongke Ni-Cu deposit, like many other copper, gold, and nickel deposits within central Asia, is related to post-eollisional extensional processes.