湖南茶陵邓阜仙花岗岩中“眼球"状析出物地球化学特征及成因  

Geochemistry and genesis of eye_shape segregations in Dengfuxian granite intrusion,Chaling,Hunan Province

作　　者：王艳丽[1,2] 祝新友[2] 杨毅 王超 程细音[2] 

机构地区：[1]有色金属矿产地质调查中心,北京100012 [2]北京矿产地质研究院,北京100012 [3]正元地理信息有限责任公司,北京101300 [4]湖南有色集团湘东钨业有限公司,湖南长沙412401

出　　处：《矿床地质》2016年第3期618-632,共15页Mineral Deposits

基　　金：国家科技支撑课题"湖南锡田地区深部成矿岩体空间结构与成矿预测(批准号:2011BAB04B08)";老矿山深部和外围找矿项目"老矿山典型矿床成矿规律总结研究(批准号:资[2014]03_001_082)";国土资源部公益性行业科研专项成矿地质体找矿预测理论研究与应用示范课题"热液矿床成矿地质体研究(课题编号:201411024_2)"联合资助

摘　　要：湖南茶陵邓阜仙岩体燕山期细粒二云母花岗岩（γⅡ）中分布大量＂眼球＂状析出物,单个＂眼球＂大小约1～3 cm,其分布呈单个的＂眼球＂独立产出,或由大量＂眼球＂连成条带,延伸可达几米至数十米。＂眼球＂状析出物具有明显的成分分带,核部＂黑眼珠＂富含黑云母（大部分蚀变为绿泥石）,边部＂白眼仁＂富含石英;＂眼球＂与花岗岩围岩（γⅡ）界线清楚截然,具有流动构造,可能是岩浆液态分异的结果。南岭主要钨矿成矿花岗岩具有高分异演化特征,同时发生液态分异作用。对比邓阜仙＂眼球＂及附近二云母花岗岩∑REE为97.83×10-6～219.37×10-6,LREE/HREE为10.41～15.29,稀土元素配分曲线呈右倾的＂V＂字形,不具有四分组效应,δEu负异常不明显,指示其演化程度不高,由此认为南岭岩浆液态分异作用主要发生在高分异演化的碱长花岗岩阶段,但在岩浆演化至二云母花岗岩阶段就已经开始,甚至可能发生的更早。岩浆液态分异作用使＂眼球＂中挥发分元素Li、F含量升高,成矿元素Cu、Pb、Zn等富集,岩浆液态分异制约着元素的迁入迁出,促进了挥发分元素以及成矿元素的富集,对矿化的形成也有一定制约作用。There are abundant eye-shape segregations in the granite body of Mesozoic Dengfuxian intrusive complex, which is situated in Chaling, Hunan Province. The single eyes are about 1--3 cm in size, and occur either as in- dependent ellipsoids or as stripes through connection. The eye-shape segregation exhibits clear boundary with the surrounding rock two-mica granite and mineral zonation; its outer part is rich in quartz and its inner part is rich in biotite, with magmatic crystallization texture. These eye-shape segregations are inferred to be the result of magma liquid immiscibility. The ore-forming granites of most tungsten deposits in Nanling are high differentia-tion magma characterized by liquid immiscibility. The geochemical characteristics of Dengfuxian granite bodies are as follow： Y;,REE= 97.83 × 10^-6--219.37× 10^-6, LREE/HREE= 10.41--15.29, and the REE patterns are right-inclined with slight depletion of 3Eu; meanwhile, the eyes are rich in ore-forming elements and volatile elements. These features suggest that the liquid immiscibility took place mainly at high differentiation stage, but had already begun during magmatic evolution into two-mica granite phase or even earlier. Liquid immiscibility process restricted the migration of elements, promoted the enrichment of volatile elements and ore-forming ele- ments, and also played some restraining effect on mineralization.

关 键 词：地球化学 “眼球"状析出物 岩浆分异 不混溶 邓阜仙 湖南省 

分 类 号：P588.121[天文地球—岩石学] P618.67[天文地球—地质学]