新疆阿尔泰库卫铜镍硫化物-钛铁氧化物复合型矿化镁铁-超镁铁质杂岩体成因  

Petrogenesis of the Kuwei Ni-Cu sulfide- and Fe-Ti oxide-bearing mafic-ultramafic intrusions in Altay,Xinjiang,NW China

作　　者：李强[1] 柴凤梅[2] 杨富全[1] 杨俊杰[2] 

机构地区：[1]中国地质科学院矿产资源研究所、国土资源部成矿作用与资源评价重点开放实验室,北京100037 [2]新疆大学新疆中亚造山带大陆动力学与成矿预测实验室,乌鲁木齐830046

出　　处：《岩石学报》2015年第8期2211-2229,共19页Acta Petrologica Sinica

基　　金：国土资源部公益性行业科研专项经费项目(201211073);国家重点基础研究发展计划"973"项目(2012CB416803)联合资助

摘　　要：库卫镁铁-超镁铁质杂岩体位于新疆阿尔泰南缘,兼具铜镍矿化岩体和钒钛铁矿化岩体的双重特征,主要组成岩石类型有中粒辉长岩、条带状橄榄辉长岩、橄榄苏长辉长岩、角闪辉长岩和含橄辉长岩等。本文采用LA-ICP-MS锆石U-Pb定年法,获得中粒辉长岩、橄榄苏长辉长岩和含橄辉长岩的加权平均年龄分别为398.7±3.7Ma、397.5±2.3Ma和385.2±1.6Ma,表明库卫岩体是早中泥盆世构造-岩浆活动的产物。岩体的主量元素显示其属亚碱性系列,并具有向拉斑系列岩石演化的趋势。具有Ba、U、Ta、Pb、Sr、Ti和Eu的正异常,Th的负异常,显示了相似的LREE相对富集的右倾型配分模式,表明它们可能为同源岩浆演化的产物。结合地球化学特征和区域地质背景,推测库卫岩体为早中泥盆世俯冲消减环境的产物,其原始岩浆可能来源于受俯冲物质交代的地幔楔和软流圈的混合体,不同的岩石类型是相似来源的岩浆经强烈分异的结果。库卫岩体兼具铜镍矿化岩体和钒钛铁矿化岩体的双重特征,但形成铁钛矿床的潜力略显不足。Kuwei Cu Ni-VTi Fe-bearing mafic-ultramafic intrusions is located in the southern margin of Altay and comprise medium grained gabbro,banded olivine gabbro,olivine norite gabbro,bojite and olivine-bearing gabbro. Zircons yielded weighted mean LAICP-MS U-Pb ages of 398. 7 ± 3. 7Ma,397. 5 ± 2. 3Ma and 385. 2 ± 1. 6Ma for medium grained gabbro,olivine norite gabbro,and olivine-bearing gabbro,respectively,indicating that they formed in the Early-Middle Devonian. Major elements show that they belong to sub-alkaline series and tend to tholeiite magma. All samples display negative anomaly of Th with enrichment of Ba,U,Ta,Pb,Sr,Ti,Eu and LREE,indicative of same source. Based on geochemistry characteristics and regional settings,we propose that Kuwei intrusion is related to subduction setting and the primitive magma was likely derived from mixture of asthenosphere mantle and mantle wedge metasomatized by subducted material. Strong magmatic differentiation from similar magma source leaded to different types of rocks. Kuwei intrusion has characteristics of both Cu-Ni mineralized intrusion and V-Ti-Fe mineralized intrusion,but lacks the potential to form a Fe-Ti deposit.

关 键 词：铜镍-钒钛铁复合型矿化 锆石U-PB定年 地球化学 库卫 岩石成因 阿尔泰南缘 

分 类 号：P588.124[天文地球—岩石学] P597.3[天文地球—地质学]