阿尔金断裂南缘约马克其镁铁-超镁铁岩的性质和年代学研究  

Characteristics and age study about the Yuemakeqi mafic-ultramagic rock in the southern Altyn Fault

作　　者：李向民[1] 马中平[1] 孙吉明[1] 徐学义[1] 雷永孝[1] 王立社[1] 段星星[1] 

机构地区：[1]西安地质矿产研究所,西安710054

出　　处：《岩石学报》2009年第4期862-872,共11页Acta Petrologica Sinica

基　　金：国家十一五科技支撑计划新疆305项目(2006BAB07B03-02);中国地质调查局青藏专项(1212010818090);中国地质调查局大调 查项目(1212010611804)资助成果

摘　　要：阿尔金南缘断裂带中的约马克其镁铁-超镁铁岩具有蛇绿岩的岩石组合特征,是卷入到阿尔金断裂带的蛇绿岩片,其下部的超镁铁质组分m/f=9.49～9.64,为镁质超基性岩;上部的镁铁质组分具有与大洋中脊玄武岩类似的REE球粒陨石标准化分布模式和微量元素原始地幔标准化分配模式,在基性岩Zr/Y-Zr和Ti/100-Zr-Y×3环境判别图解中均位于大洋中脊环境。对辉长岩进行锆石LA-ICP-MS原位U-Pb定年,表明该蛇绿岩形成于500.7±1.9Ma的晚寒武世,它们是Rodinia超大陆裂解的产物。约马克其地区铜镍综合异常中的铜异常是由产于蛇绿岩单元上部的玄武岩中铜矿化所致,而镍地球化学异常则是蛇绿岩下部单元超镁铁质组分中含镍蛇纹石引起,因而,约马克其镁铁-超镁铁岩具有找寻与蛇绿岩有关的铜矿床的可能。Yuemakeqi mafic-ultramafic rocks among the southern Altyn Fault have a similar characteristics of compares to the ophiolites', this rock belt is a slide of ophiolite that involved in the Altyn Fault. The lower ultramafic with m/f = 9.49 similar to 9.64, indicating it is a magnesium ultrabasic rock; The upper mafic has a similar characteristics to the mid-ocean ridge basalt, such as in chondrite-normalized REE diagram and primitive mantle-normalized trace elements diagram. In Zr/Y-Zr and Ti/100-Zr-Y x 3 diagram, all samples are located in the ocean ridge environment. Accord to the LA-ICP-MS zircon U-Pb dating of gabbro show that the age of this ophiolite is 500.7 +/- 1.9Ma and it formed in the Late Cambrian, it is the product of the Rodinia super-continent cracking. In Yuemakeqi region, there are copper and nickel anomalies. The copper anomaly is caused by the copper mine in the upper basalt of the ophiolite unit, and the nickel geochemical anomaly is caused by the nickel-containing serpentine in lower ultramafic of the ophiolite unit. Therefor, we would be search a copper deposit in Yuemakeqi mafic-ultramafic rock belt, which be related to the ophiolite.

关 键 词：阿尔金南缘断裂带 约马克其 镁铁-超镁铁岩 岩石学 LA-ICP-MS锆石U-PB定年 

分 类 号：P588.125[天文地球—岩石学]