Ce异常法计算岩体氧逸度的研究进展及轻稀土比值法适用性的初探  

Research Progress on Ce Anomaly Method for Calculating Oxygen Fugacity of Granite and Applicability of Light Rare Earth Ratio

作　　者：张景茹 李兴远 叶脉 ZHANG Jing-ru;LI Xing-yuan;YE Mai(Guangdong Province Academic of Environmental Science,Gnangzhou 510045,China;School of Geography and Planning,Sun Yat-sen University,Guangzhou 510275,China;Department of geology,University of Regina,Regina S4S 0A2,Canada)

机构地区：[1]广东省环境科学研究院,广东广州510045 [2]中山大学地理科学与规划学院,广东广州510275 [3]Department of geology,University of Regina,Regina Canada S4S 0A2

出　　处：《稀土》2018年第6期20-27,共8页Chinese Rare Earths

基　　金：国家自然科学基金项目(41802251,41803041)

摘　　要：氧逸度(fo2)表征了所在体系中的氧化还原程度,在诸多的地质过程中均具有重要指示意义。稀土变价元素Ce是计算岩体氧逸度的常用元素。本文首先总结了近年来利用锆石Ce异常计算氧逸度的几种方法,并指出了各个方法的优点及不足。在此基础上,统计了华南几个代表性岩体的稀土数据,计算出各个岩体的Ce/Nd及Ce/Sm值,发现成矿岩体的Ce/Nd及Ce/Sm均要明显高于非成矿岩体,并且锆石的Ce/Nd及Ce/Sm对岩体成矿专属性有明确的指示。此外,还发现锆石的Ce/Nd及Ce/Sm值与δCe呈指数形式的递增关系,由此认为岩体锆石的Ce/Nd及Ce/Sm比值能够间接表征岩体氧逸度的大小。但同时指出,目前关于岩体氧逸度的计算依然还处于经验公式阶段,都带有统计性质,因而,利用锆石Ce计算氧逸度时,要求尽可能大的数据量使结果更加准确。Oxygen fugacity (fo2 ),an intrinsic rock thermodynamic parameter,can be used to reflect the redox conditions of magmas,which exerts an important control on the speciation of multivalent elements and thus their behaviors in magmatichydrothermal processes. It is common to use Ce to estimate the fo 2 of zircon. This paper makes a comparison among different methods at first,and evaluates their advantages and limits. In addition,The Ce/Nd and Ce/Sm ratios have been applied to calculate the oxygen fugacity of represent granites in South China. Systematic differences in Ce/Nd and Ce/Sm ratios between granites related to Cu,Cu-Mo,Cu-Pb-Zn and W mineralization,and between ore-bearing and barren granites,were found. In the areas of Cu-(Au)-Mo mineralization,ore-bearing granites have higher Ce/Nd and Ce/Sm ratios than barren granites. The Ce/Nd and Ce/Sm ratios of zircon have the correlation with Ce anomalies. Based on the studies,the Ce/Nd and Ce/Sm ratios can be used as a function of oxygen fugacity compared with some other elements. However,it is pointed out that the calculation for the oxygen fugacity of granite is still in the stage of empirical formula at present. It requires as much data as possible to make the result more accurate.

关 键 词：氧逸度 Ce异常 Ce/Nd Ce/Sm 成矿岩体 

分 类 号：P584[天文地球—岩石学]