峨眉山大火成岩省白马寨镍铜硫化物矿床流体组成及地质意义

发布时间：2018-06-14 20:07

  本文选题：成矿过程 + 流体组成　； 参考：《兰州大学》2015年硕士论文

【摘要】：峨眉山大火成岩省产出了Fe-Ti-V氧化物和Ni-Cu-PGE硫化物两种类型完全不同的岩浆矿床,其成矿岩浆的氧化还原环境完全不同。白马寨镍铜硫化物矿床为富铜镍-贫PGE型地幔柱岩浆通道矿床,成矿岩体以块状硫化物为中心,依次以斜方辉石岩、二辉岩和辉长岩筒状分布,是认识岩浆通道成矿这种世界超大型镍铜硫化物矿床的主要成矿作用的理想地区。白马寨岩浆矿床相关成矿岩浆过程的流体组成系统研究可完善岩石地球化学对矿床形成过程中S饱和以及成矿元素富集的认识。本文以白马寨镍铜硫化物矿床主要成矿岩体(3号)中斜方辉石岩、二辉岩和辉长岩等3种主要岩石类型,分选辉石单矿物,采用分步加热质谱法开展了流体组份化学组成与碳同位素组成分析,探讨地幔柱成矿岩浆起源流体环境及硫饱和过程,取得了如下认识：1.白马寨镍铜硫化物矿床成矿岩体斜方辉石岩、二辉岩和辉长岩中主要岩浆矿物辉石中流体挥发份主要在200-400、400-900和900-1100℃三个温度段释出,流体释出总量分别为136.64、19870.50和996.54 mm3/g,化学组成主要以H20为主(89%),其次为CO2、H2、O2和C2H6等组分。2.从斜方辉石岩、二辉岩到辉长岩400-900℃的流体挥发份总量逐渐降低,依次为23243.3、19585.7和16782.43mm3/g,化学组成为H20、CO2、H2和O2。H2O和O2的平均含量逐渐降低,而CO2和H2的平均含量逐渐增加。3.白马寨矿床成矿岩体含碳流体挥发份的碳同位素组成变化范围较大,200-400℃温度段释出CO2和CH4的δ13CCO2介于-21.2～-9.6%o,δ13CCH4介于-54.5--34.0‰。400-900℃释出CO2和CH4的δ13CCO2介于-21.2～-9.5‰,δ13CCH4介于-49.7～-23.3‰。900-1200℃释出CO2和CH4的A13CCO2=-22.9～-0.7%o,δ13CCH4=-53.3～-20.6‰。CH4同系物碳同位素组成随碳数具有正序分布模式。4.白马寨岩体中岩浆流体组成(400-900℃)指示岩浆起源于H2O为主流体介质中,可能为赋含H2还原性流体挥发份的环境。流体挥发份中H2O、CO2和H2与Cu和Ni的含量具有正相关关系,表明大量的H2O促使源区大规模高程度部分熔融,使Cu和Ni进入成矿岩浆,CO2也有可能聚集Cu和Ni成矿金属。5.在硫化物矿体的位置H2S含量降低,H2含量相对较多,表明硫饱和促使硫化物熔离,S2-与成矿金属结合消耗了大量的硫。CO2的含量在成矿阶段有所升高,造成Fe和Ti氧化物结晶,从而降低S的溶解度,使硫化物更容易结晶。
[Abstract]:The Fe-Ti-V oxide and Ni-Cu-PGE sulfide magmatic deposits were produced in Emeishan great igneous province, and the redox environment of the ore-forming magma was completely different. The Baimazhai nickel-copper sulphide deposit is a copper-nickel-poor PGE type mantle plume magmatic channel deposit. The ore-forming rock mass is dominated by massive sulphide, followed by clinophorite, ergite and gabbro. It is an ideal area to recognize magmatic channel mineralization, which is the main metallogenic process of the world's super large nickel copper sulphide deposits. A systematic study on the fluid composition of the associated ore-forming magma process of the Baimazhai magmatic deposit can improve the understanding of the petrogeochemistry of S saturation and ore-forming element enrichment during the formation of the deposit. In this paper, the main ore-forming rock bodies (No. 3) of the Baimazhai nickel copper sulfide deposit are divided into three main rock types, I. e., metaconorite, ergite and gabbro, to separate pyroxene single minerals. The chemical composition and carbon isotopic composition of the fluid were analyzed by means of step heating mass spectrometry, and the fluid environment and sulfur saturation process of mantle plume magma were discussed. The results are as follows: 1. The magmatic pyroxene, the major magmatic mineral pyroxene in the baimazhai nickel-copper sulphide deposit, the major magmatic pyroxenes, and the fluid volatilities of the major magmatic minerals in the baimazhai nickel copper sulphide deposit were mainly released at the temperatures of 200-400400-900 and 900-1100 鈩，

本文编号：2018805