江西雅山与大吉山两类稀有金属花岗岩成矿差异性研究

发布时间：2018-02-27 22:53

本文关键词： 稀有金属花岗岩岩浆演化流体交代成矿差异性华南　出处：《中国地质大学(北京)》2016年硕士论文　论文类型：学位论文

【摘要】：江西雅山和大吉山成矿岩体都是华南典型稀有金属花岗岩,均富含W、Sn、Nb、Ta等元素,却形成不同类型矿床—雅山岩体形成我国乃至亚洲最大的钽铌矿,而大吉山花岗岩虽发育钽铌矿化,但规模和品位都远远小于雅山,而以石英脉型钨矿闻名。探究两类稀有金属花岗岩的成矿差异性对于研究华南花岗岩与成矿的关系具有重要意义。本文采集两矿床不同岩性带中的样品进行岩石学、地球化学、锆石U-Pb年代学、矿物学等方面研究,重点研究两矿床的Nb-Ta和W成矿机制,探讨岩浆演化和流体作用导致不同成矿类型的原因。研究得出如下认识:(1)雅山和大吉山花岗岩均具有亚碱、过铝、高分异演化特征。SiO2、Al2O3、Li和F等含量较高,稀土总量较低,Eu负异常和稀土元素四分组效应等都指示二者属于高分异的S型花岗岩。但雅山岩体相对具有更高的Li、F、P含量,稀土的四分组效应更显著,Eu负异常更强烈,其Rb/Sr比值更高,Nb/Ta和Zr/Hf比值较低。因此,雅山花岗岩岩浆演化程度相对更高。(2)随着岩浆不断演化,雅山花岗岩云母中的Li、F、Nb、Ta含量逐渐升高,而Fe、Mn等元素含量下降,从相对富Mg、Fe质的黑云母逐渐过渡到富F、Li的锂云母,而大吉山花岗岩中云母成分却相对单一。另外,相对于大吉山岩体,雅山岩体晚阶段的锂云母花岗岩中的长石成分更接近钠长石端元组分,且具有更高的P2O5含量,并出现富F矿物(黄玉),是岩浆高度分异演化的结果。这些矿物学特征都说明雅山岩体比大吉山花岗岩具有更高的岩浆演化程度。(3)雅山二云母花岗岩的成岩年龄为158±1.8 Ma,白云母花岗岩为156±0.4Ma,表明雅山岩体属于燕山期花岗岩。雅山花岗岩的地球化学特征、矿物学特征以及Nb、Ta元素的地球化学行为均表明Nb、Ta的成矿与花岗岩的高演化密切相关,且在岩浆演化过程中逐渐富集的F、Li、P等元素,可以增加熔体中的非桥氧数(NBO),从而进一步促进钽、铌元素的富集成矿。大吉山花岗岩演化程度低于雅山,导致其钽铌矿化规模和品位远远小于雅山,其钨矿的形成更多是受到流体作用的影响。热液流体不仅萃取W、Fe、Mn等元素,而且通过云英岩化降低氧逸度增加pH值,促进W矿的形成。岩浆演化程度的差异和流体交代作用的影响是雅山和大吉山花岗岩具有不同成矿类型的重要原因。
[Abstract]:The Yashan and Dagishan ore-forming bodies in Jiangxi Province are typical rare metal granites in South China. They are rich in elements such as WPS-SnNbTa-Ta, but form different types of deposits-the Yashan ore-body forms the largest tantalum-niobium deposit in China and even in Asia. Although tantalum and niobium mineralization is developed in the Dagishan granite, its scale and grade are far smaller than that in Yashan. It is very important to study the relationship between granites and mineralization in South China. In this paper, samples from different lithologic zones of the two deposits are collected for petrology and geochemistry. Zircon U-Pb geochronology, mineralogy and other aspects are studied, with emphasis on the Nb-Ta and W metallogenic mechanism of the two deposits. The causes of different metallogenic types caused by magmatic evolution and fluid action are discussed. The results show that both the Yashan and Dagishan granites have higher contents of alkali, peraluminite, and high differentiation, such as Al 2O 3 Li and F, etc. The negative anomaly of EU and the four-group effect of rare earth elements indicate that both of them belong to highly differentiated S-type granite. However, the Yashan rock mass has a higher content of Li-FU P, and the four-group effect of rare earth elements is more significant, and the negative anomaly of EU is stronger. The Rb/Sr ratio is higher and the ratios of NB / Ta and Zr/Hf are lower. Therefore, the magmatic evolution degree of Yashan granite is relatively higher. The content of mica in the Dagishan granite is relatively single, in addition, it is relative to the Dagi massif, and the content of the mica in the Dagishanite granite is relatively simple, in addition, the content of the mica in the Daguishan granite is relative to that of the Dagi mountain body. The feldspar composition of the spodolite granite in the late stage of the Yashan rock body is closer to the end component of albite and has higher P _ 2O _ 5 content. These mineralogical characteristics indicate that the Yashan granite has a higher magmatic evolution degree than the Dagishan granite, and the diagenetic age of the Yashan mica granite is higher than that of the Dagishan granite. It is 158 卤1.8 Ma and 156 卤0.4 Ma for Muscovite granite and Muscovite granite, indicating that the Yashan granite belongs to Yanshanian granite and the geochemical characteristics of Yashan granite. The mineralogical characteristics and the geochemical behavior of the element NbGTA indicate that the mineralization of NB Ta is closely related to the high evolution of the granite, and the elements such as Fangliang P, which are gradually enriched during the magmatic evolution, are closely related to the mineralization of NbTa-Ta. Thus, the enrichment and mineralization of tantalum and niobium elements can be further promoted. The evolution degree of the Dagishan granite is lower than that of Yashan, resulting in the mineralization scale and grade of tantalum and niobium is much smaller than that in Yashan. The formation of tungsten ore is more affected by fluid action. Hydrothermal fluid not only extracts elements such as WFE mn, but also increases pH value by reducing oxygen fugacity by quartz rock. The difference of magmatic evolution degree and the influence of fluid metasomatism are the important reasons for the different metallogenic types of Yashan and Dagishan granites.
【学位授予单位】：中国地质大学(北京)
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：P618.6

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