摘要
为厘清努日铜钼钨矿床的成矿时代,以矿床中的辉钼矿为研究对象,用ICP-MS分析方法,开展了稀土元素和微量元素地球化学研究。结果显示,辉钼矿具有典型的轻重稀土分馏、轻稀土元素(LREE)富集的右倾配分模式,辉钼矿稀土元素具有强烈的Ce负异常和Eu负异常,前者可能为成矿流体本身具有高温高氧逸度导致,后者可能是与矽卡岩矿化有密切关系的黑云母花岗闪长岩浆在分离结晶过程中大量的斜长石晶出引起的,同时岩体蚀变过程中对成矿流体体系亏损铕有一定贡献。辉钼矿中Pb、Ba、V、Ni、Sr、Rb含量相对较高,U、Th含量非常低,Hf/Sm、Th/La远小于1,Nb/La远大于1,表明成矿流体早期以富F的来自于深部幔源的岩浆热液为主,而Y/Ho、Zr/Hf、Nb/Ta变化范围存在不同幅度的差异。表明主成矿期成矿流体在该阶段不同程度的混入了部分外来流体而富Cl,但总体特征仍以早期成矿流体为主。
Geochemical characteristics of rare earth and trace elements in the molybdenite were studied with ICP-MS method to identify the metallogenic epoch of the Nuri Cu-Mo-W Deposit. The results showed that the light and heavy REEs were fractionated obviously,molybdenite was low with negative cerium and europium anomalies that was characterized by enrichment in light REE. The former found ore-forming fluid had the characteristics of high temperature and high oxygen fugacity,and the latterwas caused by plagioclase crystal in the process of biotite monzonitic granite magma separation and crystallization which had close contact with the skarn,meanwhile gain the contribution from the process of rock alteration.The contents of Pb,Ba,V,Ni,Sr and Rb were relatively high but contents of U and Th were very low. The enrichment indexes of LREE,Hf/Sm and Th/La were far less than 1 while that of Nb/La was greater than 1,indicating that the mantle-derived ore-forming fluid was F-rich in the early,and that the Y/Ho,Zr/Hf and Nb/Ta varied differently. All of which indicated that,in the main metallogenic epoch,the ore-forming fluid was mixed with some external Cl-rich fluid but still showed the characteristic of the early stage fluids.
出处
《矿物岩石地球化学通报》
CAS
CSCD
北大核心
2015年第3期564-570,共7页
Bulletin of Mineralogy, Petrology and Geochemistry
基金
中国地质调查局地调项目(1212011221073
2011CB403105
12120114050501)
关键词
辉钼矿
稀土元素
微量元素
成矿流体
西藏
molybdenite
rare earth elements
trace elements
ore-forming fluid
Tibet
