扬子西南缘拉拉IOCG矿床辉钼矿稀土元素地球化学特征  

REE geochemistry of molybdenite in the Lala IOCG deposit, southwestern margin of the Yangtze block

作　　者：刘晓文 李泽琴[1] 王奖臻[1] 黄从俊[1] LIU Xiao-wen;LI Ze-qin;WANG Jiang-zhen;HUANG Cong-jun(School of Earth Science, Chengdu University of Technology, Chengdu 610059, China)

机构地区：[1]成都理工大学地球科学学院,四川成都610059

出　　处：《地球化学》2018年第3期288-294,共7页Geochimica

基　　金：国家自然科学基金(41072065);教育部博士点基金(20105122110001);中国地质调查局项目(12120113095500)

摘　　要：本文以扬子西南缘拉拉IOCG矿床辉钼矿为研究对象,应用电感耦合等离子体质谱法(ICP-MS),对变质热液期浸染状辉钼矿(Ⅰ)及后期热液期团块状辉钼矿(Ⅱ)中稀土元素(REE)进行了研究。两期辉钼矿具明显不同的矿/岩相学及REE特征:辉钼矿(Ⅰ)镜下呈鳞片状、规则的板柱状、弯曲的板柱状集合体;辉钼矿(Ⅱ)晶体粗大且结晶程度较高,镜下呈片状集合体。辉钼矿(Ⅰ)的∑REE明显高于辉钼矿(Ⅱ),但轻、重稀土分异程度低于辉钼矿(Ⅱ);辉钼矿(Ⅰ)具Eu负异常特征,而辉钼矿(Ⅱ)表现为Eu正异常、Ce负异常。研究认为:辉钼矿(Ⅰ)的Eu负异常主要受控于成矿流体本身的性质,成矿流体的形成温度较高;辉钼矿(Ⅱ)的Eu正异常、Ce负异常主要受控于成矿流体所处的物理化学环境,并暗示其成矿流体为较低温、高氧逸度的流体。两期辉钼矿分别源于不同的成矿流体。In order to study the molybdenite characteristics of the Lala IOCG deposit in the western margin of the Yangtze Block, rare earth elements（REEs） in the disseminated molybdenite（Mo Ⅰ） of the metamorphic hydrothermal stage, and friable molybdenite（Mo Ⅱ） of the late hydrothermal stage were studied using inductively coupled plasma mass spectrometry（ICP-MS） in this paper. Results show that the molybdenites from the two stages have distinctive mineralographic, petrographic, and REE features. Mo Ⅰ occurs as aggregates of flaky, normal tabular, and curved tabular crystals; Mo Ⅱ occurs as flaky aggregates of relatively coarse crystals and high crystallinity. REE concentrations of Mo I are observably higher than those of Mo Ⅱ, and for Mo Ⅱ, the degree of fractionation of light and heavy REEs is higher than that of Mo Ⅰ. Mo Ⅰexhibits a negative Eu anomaly, and Mo Ⅱ exhibits a positive Eu anomaly. These studies suggest that： Mo Ⅰ exhibits negative Eu anomalies, which are mainly controlled by the fluid itself, suggesting a high formation temperature of the ore-forming fluid; Mo Ⅱ exhibits positive Eu anomalies and negative Ce anomalies, which are mainly controlled by the physical and chemical environment, indicating that the ore-forming fluid was characterized by high oxygen fugacity. These two molybdenites were derived from different ore-forming fluids.

关 键 词：IOCG矿床 辉钼矿 稀土元素 地球化学 

分 类 号：P611[天文地球—矿床学] P595[天文地球—地质学]