投稿时间：2012-08-12
修订日期：2012-08-31
中文摘要:新疆阿吾拉勒成矿带西段的众多铜矿床可分为2种类型,即中、南部的次火山岩型和北部的中-低温热液脉型。文章对从南到北的2种类型的5个铜矿床(穷布拉克、奴拉赛、群吉、群吉萨依、109)进行了系统的碳、氧、硫、铅同位素研究,探讨了成矿物质来源及成矿环境。测试结果表明:次火山岩型矿床内硫化物的δ34S值变化很小,南部和中部的矿床分别为3.4‰~4.4‰和-1.6‰~0.2‰,反映出其来源单一,以岩浆源或地幔源为主;中-低温热液脉型矿床内硫化物的δ34S值变化较大,为-18‰~8.9‰,具有多源性。次火山岩型矿床内方解石的δ13C值为-1.44‰~0.8‰,δ18O值为11.87‰~16.99‰,可能为深源流体与碳酸盐岩地层发生一定反应的结果;中-低温热液脉型矿床内方解石的δ13C值为-10.1‰~-3.2‰,δ18O值为9.63‰~16.27‰,整体以幔源为主。中-低温热液脉型铜矿床内矿石铅为正常铅,以地幔铅占主导地位;赋存于酸性次火山岩中的次火山岩型铜矿床的矿石铅为富含放射性成因铅的异常铅,来源于前寒武系基底岩石;赋存于基性次火山岩中的次火山岩型铜矿床的矿石铅为壳幔混合铅,受到了地壳物质的强烈混染。这2种类型铜矿床的成矿物质来源表现出从南到北的明显差异,这种差异与各矿床赋矿地层和岩性组合的不同有很好的对应关系,反映了铜矿带南北成矿环境的不同。由于该区与铜矿有关的陆相(次)火山岩为晚石炭世-二叠纪伊犁古裂谷演化的产物,这可能揭示了区域成矿与二叠纪的裂谷演化紧密相关。在裂谷演化的不同阶段,该铜矿带南部和北部的构造体系具有不同的开放程度,从而形成了不同的火山岩组合和沉积地层,即矿源层。矿源层的差异和火山活动的强弱决定了在裂谷带南北不同部位形成了不同类型特征的铜矿床。
Abstract:The copper deposits distributed in western Awulale Mountain metallogenic belt include subvolanic rock-related Cu deposits (SVR) situated in the middle and southern area and intermediate-low temperature hydrothermal vein-type Cu deposits (ILTHV) located in the northern area. This paper reports a detailed C, O, S and Pb isotopic investigation of three SVR deposits (No.109, Qunjisayi and Qunji) and two ILTHV deposits (Nulasai and Qiongbulake) lying from south to north in the ore field. The sulfur isotopic compositions of the sulfides from the five deposits show distinct differences and systematic variations from south to north. The SVR deposits show small variation of δ34S values from +3.4‰ to +4.4‰ (No. 109 deposit) and from -1.6‰ to 0.2‰ (Qunjisayi and Qunji deposits). In contrast, the ILTHV deposits have large variation of δ34S values from -18‰ to +8.9‰. The carbon and oxygen isotope variations of the two types have similar sulfur isotope variation features. The SVR deposits show small variation of δ13C values from -1.44‰ to +0.8‰ and relatively large variation of δ18O values from +11.87‰ to +16.99‰. The ILTHV deposits have large variation of δ13C values from -10.1‰ to -3.2‰ and relatively large variation of δ18O values from 9.63‰ to 16.27‰. The Pb-isotopic composition of sulfides from ILTHV deposits indicate that they are normal-Pb mainly derived from the mantle. The Pb-isotope of sulfides from felisic SVR deposits is rich in radiogenetic Pb provided by the Precambrian basement rock. The Pb-isotope of sulfides from basic SVR deposits is the mixed mantle-Pb and crust-Pb. In conclusion, the systematic variations of mineral source and ore-forming process from SVR deposits to ILTHV deposits reveal that the metallogenic environments in southern and northern copper belt are different and this difference was probably related to the Permian rifting evolution. In the process of Permian rifting evolution, the different extents of the stretching structure in southern and northern copper belt caused different volcanic rocks and sedimentary strata which constituted the ore-source bed. The formation of different Cu deposit types in different positions was controlled by the difference in mineral sources and intensities of continental volcanism caused by the Permian rifting.
keywords:geochemistry stable isotope mineral source metallogenic environment western Awulale Mountain metallogenic belt Xinjiang
文章编号：
中图分类号：P618.41
文献标志码：
基金项目:本文得到国家科技支撑计划(编号: 2011BAB06B02-05)和地质矿产调查评价项目(编号: 1212011085060)的联合资助
引用文本：
赵军,张作衡,刘晓阳,刘敏,张贺,朱维娜.2012.新疆阿吾拉勒成矿带西段铜矿床碳、氧、硫、铅同位素研究——成矿物质来源及成矿环境探讨[J].矿床地质,31(5):999~1013ZHAO Jun,ZHANG ZuoHeng,LIU XiaoYang,LIU Min,ZHANG He,ZHU WeiNa.2012.Carbon, oxygen, sulfur and lead isotope constraints on the ore source and metallogenesis of copper deposits in western Awulale Mountain metallogenic belt, Xinjiang[J].Mineral Deposits31(5):999~1013
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