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

发布时间：2018-03-14 02:20

本文选题：锆石U-Pb年龄　切入点：矿物岩石地球化学　出处：《地质学报》2017年04期 　论文类型：期刊论文

【摘要】：新疆东天山铜镍成矿带铜镍总储量达百万吨,是我国重要的铜镍矿集区。以往的研究多集中在成矿带的东段和中段,而本文选择成矿带西段的典型岩体进行详细的地质年代学、矿物学和岩石地球化学研究。东天山铜镍成矿带西段镁铁—超镁铁质岩体以大草滩和白鑫滩岩体为代表,可分为四种岩相:闪长岩相、辉长岩相、橄榄辉长岩相和橄榄岩相,其中橄榄岩相为主要含矿岩相。白鑫滩岩体橄榄辉长岩锆石U-Pb年龄为286.4±1.6Ma,与岩体含长辉石橄榄岩(~278 Ma)相差~7 Ma。大草滩和白鑫滩岩体样品主量元素投影点都处于主要造岩矿物化学成分之间,表明岩体的主量元素主要受堆晶矿物控制。大草滩和白鑫滩岩体的微量元素标准化图解与东天山典型成矿岩体相似,均具有明显的Nb,Ta亏损,且具有较高的ε_(Nd)(t)值(+6.01~+8.9,t=286 Ma)和ε_(Hf)(t)值(+11.62~+16,t=286 Ma)。大草滩和白鑫滩岩体岩浆源区是软流圈上涌导致被俯冲事件改造的交代地幔发生部分熔融的产物。岩体橄榄石Fo值与Ni的关系表明岩浆在橄榄石结晶过程中存在硫化物熔离。模拟计算表明上述岩体母岩浆在上侵过程中在深部与新生的岛弧地壳发生5%~15%的混染后达到了硫饱和,造成了硅酸盐岩浆PGE的亏损。分离结晶和地壳硫的加入是导致岩浆在地壳层位发生二次熔离的主要因素。不同岩相的年龄数据表明大草滩和白鑫滩岩体形成于多期次岩浆作用,有助于形成具有经济价值的铜镍矿体。对比可得新疆东天山铜镍成矿带西段的镁铁—超镁铁质岩体的年龄和硫化物饱和过程与东段和中段的成矿岩体相似,故成矿带西段有寻找大中型铜镍硫化物矿床的潜力。
[Abstract]:The copper-nickel metallogenic belt in East Tianshan of Xinjiang has a total reserves of 1 million tons and is an important copper-nickel ore concentration area in China. In the past, most studies focused on the eastern and middle sections of the metallogenic belt, but in this paper, the typical rock mass in the western section of the metallogenic belt is selected for detailed geochronology. Mineralogical and petrogeochemical studies. The mafic and ultramafic rocks in the western section of the Cu-Ni metallogenic belt of East Tianshan are represented by the Dachaotan and Baixintan pluton, which can be divided into four lithofacies: diorite facies, gabbro facies, olivine gabbro facies and peridotite facies. The zircon U-Pb age of olivine gabbro in Baixintan is 286.4 卤1.6 Ma, which is different from that of pyroxene at 278 Ma. The main element projection points of Dachaotan and Baixintan are in the main. Between the chemical composition of rock-forming minerals, The results show that the main elements of the rock mass are mainly controlled by the heap minerals. The standardized diagrams of trace elements in the Dachaotan and Baixintan are similar to those in the typical ore-forming rocks of the East Tianshan Mountains, and both have obvious Nbta-Ta depletion. The magmatic source region of the Dachaotan and Baixintan pluton is the product of partial melting of the metasomorphic mantle caused by the upwelling of the asthenosphere and the transformation of subduction events by the upwelling of the asthenosphere (6.01 ~ 8.9 ~ 8.9 ~ 286MaA) and the value of 蔚 ~ (-1) HfTX / t (11.62-16) Math. the magmatic source region of the Dacaotan and Baixintan pluton is the product of partial melting of the metasomatic mantle which has been transformed by subduction events due to the upwelling of the asthenosphere. The relation of Ni indicates that sulfide melting occurs during the crystallization of olivine magma. The simulation results show that the parent magma of the above mentioned rock mass has reached sulfur saturation after 5% mixing in the deep layer and the new island arc crust during the upwelling of the magma. The main factors leading to the secondary melting of magma in the crust are the separation crystallization and the addition of sulfur in the crust. The age data of different lithofacies indicate that the Dachaotan and Baixintan intrusions were formed in multi-stage magmatism. The age and sulphide saturation process of the magnesia-ultramafic rock body in the western section of the eastern Tianshan copper and nickel metallogenic belt in Xinjiang is similar to that of the ore-forming rock body in the eastern and middle segments, which is helpful to the formation of copper and nickel orebodies of economic value. Therefore, the west part of the metallogenic belt has the potential to look for large and medium-sized copper-nickel sulphide deposits.
【作者单位】：长安大学地球科学与资源学院;国土资源部岩浆作用与找矿重点实验室;云南大学资源环境与地球科学学院;陕西省核工业地质调查院;
【基金】：中国地质调查局地质调查项目(编号:1212011085061) 国家自然科学基金(编号:41372101,41402070)共同资助成果
【分类号】：P618.41;P618.63;P581

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