四川杨柳坪岩浆型铜镍硫化物矿床成矿作用研究

发布时间：2018-03-21 00:35

  本文选题：铜镍硫化物矿床　切入点：地球化学　出处：《中国地质大学(北京)》2017年硕士论文　论文类型：学位论文

【摘要】：本次工作研究的对象为杨柳坪铜镍硫化物矿床。本文紧扣岩浆硫化物矿床的几个关键性问题:矿床的年代学研究、岩浆源区的性质、是否有同化混染作用及混染程度等,通过岩石学、矿物学、元素地球化学以及同位素地球化学方法对岩体进行系统研究,主要获得以下几方面的成果:(1)前人通过测试县城北边残坡积层中弱变质的基性超基性岩中的金云母,获得的等时线年龄为40Ar/39Ar坪年龄250.2±1.9Ma,推测该矿床为二叠纪峨眉地幔柱的产物。但本次工作通过对杨柳坪铜镍硫化物矿石中磁黄铁矿进行Re-Os同位素测年,获得等时线年龄数据为375±63Ma(MSWD=9.2),该数据表明与峨眉山大火成岩省主喷发期不同,推测为一次独立的成矿事件。根据其年龄及其微量元素构造环境判别图初步推断该矿床的形成环境为岛弧环境。(2)SiO2与氧化钙(CaO)、全碱(Na2O+K2O)以及氧化铝(Al2O3)、氧化钛(TiO2)呈正相关关系,与氧化镁(MgO)和氧化铁(TFeO)呈负相关关系,反映出发生了斜长石、单斜辉石、橄榄石的分离结晶作用;δEu与氧化钙(CaO)、氧化铝(Al2O3)、锶(Sr)呈正相关关系表明岩浆演化过程中斜长石的分离结晶作用;MgO与各主要氧化物的相关性表明超镁铁单元应该发生了橄榄石的分离结晶作用,而镁铁单元则发生了少量斜方和单斜辉石的分离结晶。(3)S同位素组成变化范围比较小,说明成矿物质的均一化程度很高。S同位素变化范围为-2~+2‰,其特征表明成矿物质为幔源硫;87Sr/86Sr初始比值较高,187Os/188Os初始比值为0.1469±0.0037,γOs值介于26~46之间,206Pb/204Pb和207Pb/204Pb比值比较一致,208Pb/204Pb比值变化比较大,岩体的Nb/U值为1.2~30.7,平均为17.8;Ce/Pb值为0.59~10.124,平均为3.65等特征表明发生了地壳物质的同化混染作用。
[Abstract]:The object of this work is Yangliuping copper-nickel sulfide deposit. This paper focuses on several key problems of magmatic sulfide deposit, such as the chronological study of the deposit, the nature of the magma source, whether there is assimilation and the degree of the mixed contamination, etc. Through petrology, mineralogy, element geochemistry and isotopic geochemistry, a systematic study of the rock mass was carried out. The main achievements are as follows: 1) by testing the biotite in the weakly metamorphosed basic ultrabasic rocks in the residual slope accumulation in the north of the county town, The isochron age of 40Ar39 ar plateau is 250.2 卤1.9Ma. it is assumed that the deposit is a product of the Permian Emei mantle plume. However, the Re-Os isotopic dating of pyrrhotite in Yangliuping copper-nickel sulfide ore is carried out in this work. The isochron age data obtained is 375 卤63 Ma MSWDX 9.2g, which indicates that the age data are different from the main eruption period of Emeishan great igneous rock province. It is inferred that the formation environment of the deposit is a positive correlation between the island arc environment, CaOO _ 2, Na2OK _ 2O _ 2 and Al _ 2O _ 3, TIO _ 2 and TIO _ 2, according to the age and trace element tectonic environment discriminant diagram of the deposit, which is supposed to be an independent metallogenic event, and the formation environment of the deposit is positively correlated with the CaOO _ 2, Na _ 2O _ 2, Al _ 2O _ 3 and Ti _ 2O _ 2. There is a negative correlation with MgO and TFeO, which indicates that plagioclase, clinopyroxene and clinopyroxene occur. The separation and crystallization of olivine and the positive correlation between 未 EU and Cao, Al _ 2O _ 3, Sr ~ (2 +) indicate that the separation and crystallization of plagioclase and the correlation between MgO and major oxides during magmatic evolution indicate that ultramagnesia-iron unit should occur. The separation and crystallization of olivine, On the other hand, a small amount of clinopyroxene and clinopyroxene occur in the magnesium-iron unit, and the variation range of the isotopic composition is relatively small, indicating that the degree of homogenization of the ore-forming material is very high. The variation range of S isotope is -2 ~ 2 鈥，

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