地质学报2017，Vol.91Issue(4)：792-811,20.
新疆东天山铜镍成矿带西段镁铁—超镁铁质岩体成因及成矿潜力研究
Genesis and Ore-forming Potential of Mafic-Ultramafic Intrusions in the Western Part of East Tianshan Cu-Ni Metallogenic Belt, Xinjiang
摘要
Abstract
East Tianshan Cu-Ni metallogenic belt,containing ＞1 million metric tons (Mt),is an important ore-cluster area in China.Different from previous studies,which mainly focused on the eastern and central parts of this belt,this paper chose the typical intrusions in the western part to carry out an integrated geochronological,mineralogical and geochemical study.The major lithofacies of the western part represented by Baixintan and Dacaotan intrusions are diorite,gabbro,olivine gabbro and peridotite which host disseminated sulfide ore deposits.The zircon U-Pb age is 286.4±1.6 Ma for Baixintan olivine gabbro rock samples,which is ～7 Ma older than the pyroxene peridotite rock samples.Major elements of the samples from Dacaotan and Baixintan intrusions are plotted in the chemical composition area of main rock-forming minerals,indicating that the oxide compositions of rock samples are controlled by these cumulus minerals.Chondrite-normalized REE patterns and primitive mantle-normalized trace element patterns of the Dacaotan and Baixintan intrusions are similar to that of typical Ni-Cu-bearing intrusions in the East Tianshan area,with depletion in Nb and Ta,high εNd(t) values from +6.01 to +8.9 and zircon εHf(t) values from +11.62 to +16.All these characteristics indicate that the magma sources of the Dacaotan and Baixintan intrusions were the product of partial melting of metasomatized mantle,which was reformed by subduction event resulting from uprising of asthenosphere.Relation of Fo value and Ni contents of olivine in ultramafic rocks from the Dacaotan and Baixintan intrusions suggests that sulfide liquation occurred during the process of olivine crystallization.Numerical modeling calculation indicates that the parental magma of the Dacaotan and Baixintan intrusions reached sulfide saturation after mixing at depth with 5 ％～ 15％ juvenile arc crust during uprising process,causing the depletion of PGE in silicate magma.Fractional crystallization and addition of external sulfide should be the leading factor for triggering the second liquation of magma in the crust.The age data of the different lithofacies samples indicate that the Dacaotan and Baixintan intrusions formed from multistage magmatism,which contributes to the formation of Cu-Ni sulfide orebodies with high economic value.Comparison study shows that mafic-ultramafic intrusions in the western part of East Tianshan Cu-Ni metallogenic belt have similar age and sulfide saturation process as ore-forming intrusions in the eastern and middle parts of East Tianshan.Therefore,the western part of East Tianshan Cu-Ni metallogenic belt has great potential for medium-or large-sized Cu-Ni sulfide deposits.关键词
锆石U-Pb年龄/矿物岩石地球化学/镁铁质—超镁铁质岩石/白鑫滩岩体/大草滩岩体/东天山铜镍成矿带Key words
zircons U-Pb age/mineral and whole-rock geochemistry/mafic-ultramafic rocks/Baixintan intrusion/Dacaotan intrusions/East Tianshan Cu-Ni metallogenic belt引用本文复制引用
冯延清,钱壮志,段俊,孙涛,徐刚,姜超,任萌,陈宏骏..新疆东天山铜镍成矿带西段镁铁—超镁铁质岩体成因及成矿潜力研究[J].地质学报,2017,91(4):792-811,20.基金项目
本文为中国地质调查局地质调查项目(编号:1212011085061)和国家自然科学基金(编号:41372101,41402070)共同资助成果. （编号:1212011085061）
