江西大湖塘钨矿花岗岩的磷灰石特征及其氧逸度变化指示  

Oxygen fugacity variation recorded in apatite of the granite in the Dahutang tungsten deposit,Jiangxi Province,South China

作　　者：韩丽[1,2] 黄小龙[1] 李洁[1,3] 贺鹏丽[1,2] 姚军明[4] 

机构地区：[1]中国科学院广州地球化学研究所,同位素地球化学国家重点实验室,广州510640 [2]中国科学院大学,北京100049 [3]国家海洋局第二海洋研究所,海底科学实验室,杭州320012 [4]中国科学院广州地球化学研究所,矿物学与成矿学重点实验室,广州510640

出　　处：《岩石学报》2016年第3期746-758,共13页Acta Petrologica Sinica

基　　金：国家"973"计划项目(2012CB416703);国家自然科学基金创新研究群体项目(41421062)联合资助

摘　　要：赣西北地区大湖塘钨多金属矿集区赋含世界级的超大型钨矿,其成矿作用与中生代花岗质岩浆活动密切相关。大湖塘钨多金属成矿区南部的狮尾洞钨矿床的各类花岗岩中普遍发育磷灰石。黑云母花岗岩中的磷灰石成分均匀,而白云母花岗岩和锂云母花岗岩中的磷灰石受到流体作用具有环带结构。环带结构磷灰石的核部为岩浆结晶的产物,具有较低的Mn O（0.68%～1.69%）,而边部为受后期流体交代作用的产物,具有明显较高的Mn O（3.59%～8.28%）。在岩浆演化过程中,Mn以高价态阳离子（Mn5＋）的形式置换P5＋进入磷灰石,而在热液环境主要以低价态阳离子（Mn2＋）的形式置换Ca2＋进入磷灰石,表明流体作用导致体系环境从高氧逸度转变为低氧逸度。黑云母内部残留的原生金红石具有相对高的Zr含量,其形成温度为680～760℃,代表了相对较高的岩浆温度;而生长在黑云母边部并围绕钛铁矿或与金属硫化物共生的次生金红石具有相对低的Zr含量,对应于后期热液作用的较低温度（〈490℃）。本文研究表明,岩浆活动后期的流体作用可能导致了体系氧逸度和温度的降低,将有利于钨矿形成。The Dahutang tungsten polymetallic ore region,in northwestern Jiangxi Province,South China,has the super-large tungsten mine of the world,which is closely related to the Mesozoic granitic magmatism. As a ubiquitous accessory mineral in the Mesozoic granites from the Shiweidong tungsten deposit in the southern part of the Dahutang region,apatite is homogeneous in biotite granite,but shows zoning structure in muscovite granite and lepidolite granite due to fluid metasomatism. In general,the cores of zoning apatites crystallized during the magma evolution contain distinctly lower Mn O（ 0. 68% ～ 1. 69%） than the rims（ Mn O = 3. 59%～ 8. 28%） affected by fluid metasomatism. During the magma evolution,highly charged ion of Mn5 ＋replaces P5 ＋into the apatite. On the contrary,low valence Mn2 ＋replaces Ca2 ＋into the apatite under hydrothermal condition. This indicates that the oxygen fugacity of the melt system changes from high to low value due to fluid activity. Primary rutile reserved in the interior of biotite contains relatively high Zr,corresponding to higher temperatures（ 680 ～ 760℃） of the granitic magma; the secondary rutile around ilmenite or accompanied with metal sulfide along the rim of biotite has relatively low Zr,agreeing with lower temperatures（ 490℃） of the hydrothermal activity. Therefore,the post-magmatism fluid activity might benefit the tungsten mineralization through reducing the oxygen fugacity and temperature of the melt system.

关 键 词：钨矿 流体作用 氧逸度 磷灰石 金红石 大湖塘 华南 

分 类 号：P575.1[天文地球—矿物学] P597.3[天文地球—地质学]