塔里木克拉通北缘兴地镁铁—超镁铁质岩带铜镍成矿作用:来自铂族元素地球化学的制约  

Cu-Ni Mineralization of Xingdi Mafic-ultramafic Rock Belt in the Northern Tarim Craton,China:Constraints from PGE Geochemistry

作　　者：夏昭德[1,2,3] 胡秀军[4] 杜玮[1,2,3] 夏明哲 汪帮耀[1,2,3] 焦建刚[1,2,3] 张朋[4] 王厚方[4] XIA Zhao-de;HU Xiu-jun;DU Wei;XIA Ming-zhe;WANG Bang-yao;JIAO Jian-gang;ZHANG Peng;WANG Hou-fang(School of Earth Science and Resources,Chang'an University,Xi'an 710054,Shaanxi,China;Key Laboratory of Western China's Mineral Resources and Geological Engineering of Ministry of Education,Chang'an University,Xi'an 710054,Shaanxi,China;Xi'an Key Laboratory for Mineralization and Efficient Utilization of Critical Metals,Chang'an University,Xi'an 710054,Shaanxi,China;No.3 Geological Party,Xinjiang Bureau of Geology&Mineral Resources,Ku erle 841000,Xinjiang,China)

机构地区：[1]长安大学地球科学与资源学院,陕西西安710054 [2]长安大学西部矿产资源与地质工程教育部重点实验室,陕西西安710054 [3]长安大学西安市关键金属成矿与高效利用重点实验室,陕西西安710054 [4]新疆地质矿产勘查开发局第三地质大队,新疆库尔勒841000

出　　处：《地球科学与环境学报》2023年第5期1118-1131,共14页Journal of Earth Sciences and Environment

基　　金：中央高校基本科研业务费专项资金项目(300102279210);陕西省自然科学基础研究计划项目(2021JM-160);中国地质调查局地质调查项目(DD20190065)。

摘　　要：兴地镁铁—超镁铁质岩带位于塔里木克拉通北缘的库鲁克塔格地块,由兴地Ⅰ号、Ⅱ号、Ⅲ号和Ⅳ号等岩体组成。其中,兴地Ⅰ号和Ⅳ号岩体以辉长岩相为主;而兴地Ⅱ号和Ⅲ号岩体从橄榄岩相、辉石岩相到辉长岩相均有产出,岩相分带清楚。兴地Ⅱ号和Ⅲ号岩体二辉橄榄岩和二辉岩中均赋存有铜镍硫化物矿(化)体,常见矿石构造有星点状、斑点状、稀疏浸染状和稠密浸染状等,金属硫化物以磁黄铁矿、镍黄铁矿和黄铜矿为主。兴地Ⅱ号和Ⅲ号岩体岩石的铂族元素(PGE)含量(质量分数,下同)((0.41~4.54)×10^(-9))低,钯组铂族元素(PPGE)含量总体高于铱组铂族元素(IPGE),IPGE/PPGE值为0.08~0.48,原始地幔标准化铂族元素蛛网图呈左倾型。岩石中铂族元素相对于Ni和Cu明显亏损,Pd/Ir值为3.28~23.33,Ni/Cu值为3.67~10.00,表明其母岩浆为高镁玄武质岩浆,这与橄榄石-熔体平衡估算的母岩浆性质一致。全岩Cu/Pd值((6.58~83.33)×10^(4))以及Cu/Zr值与Ni含量的相关性特征表明,在岩浆源区和侵位过程中均发生了硫化物的熔离作用,导致残余岩浆中显著亏损铂族元素。综合分析认为,兴地Ⅱ号和Ⅲ号岩体具有良好的找矿前景。Xingdi mafic-ultramafic rock belt in the northern Tarim craton is composed of No.Ⅰ,No.Ⅱ,No.Ⅲand No.Ⅳintrusions.The lithology of Xingdi No.Ⅰand No.Ⅳintrusions is mainly gabbro facies,while Xingdi No.Ⅱand No.Ⅲintrusions have various rocks of olivine,pyroxenite and gabbro facies,and the lithofacies zonation is clear.The Cu-Ni sulfide ore bodies are mainly hosted in lherzolite and websterite of Xingdi No.Ⅱand No.Ⅲintrusions,and the Cu-Ni sulfide ores are stellate,speckled,sparse-disseminated and dense-disseminated in structure.Most of the sulfides occur as aggregate of pyrrhotite,pentlandite and chalcopyrite.The total contents of platinum group element(PGE)are(0.41-4.54)×10^(-9) of bulk rocks in Xingdi No.Ⅱand No.Ⅲintrusions,which are lower than that of primitive mantle and show positive correlations with MgO contents.The contents of IPGE(Os,Ir and Ru)are slightly higher than that of PPGE(Ru,Pt and Pd)with IPGE/PPGE ratios of 0.08-0.48,and primitive mantle-normalized PGE spider diagrams of rocks are left-declined pattern.Their Pd/Ir and Ni/Cu ratios range from 3.28 to 23.33 and from 3.67 to 10.00,respectively,indicating that parental magmas of Xingdi No.Ⅱand No.Ⅲintrusions are high-Mg basaltic.It is consistent with the result estimated from olivine-melt equilibrium.According to bulk rock Cu/Pd ratio((6.58-83.33)×10^(4))and correlation between Cu/Zr and Ni,it is concluded that sulfide dissociation occurs in the source and during emplacement,resulting in a significant loss of PGE in remnant magma.It is comprehensively concluded that Xingdi No.Ⅱand No.Ⅲintrusions have good prospecting prospect.

关 键 词：铜镍矿 铂族元素 矿石结构 硫化物 母岩浆 成矿作用 塔里木克拉通 

分 类 号：P578[天文地球—矿物学] P618[天文地球—地质学]