江西宜春黄玉-锂云母花岗岩中的铍矿化作用:铍磷酸盐矿物组合  

Beryllium mineralization in the Yichun topaz-lepidolite granite, Jiangxi:Associations of beryilium phosphate minerals

作　　者：车旭东[1] 王汝成[1] 胡欢[1] 张文兰[1] 黄小龙[2] 

机构地区：[1]南京大学地球科学系内生金属矿床成矿机制研究国家重点实验室,南京210093 [2]中国科学院广州地球化学研究所,广州510640

出　　处：《岩石学报》2007年第6期1552-1560,共9页Acta Petrologica Sinica

基　　金：国家自然科学基金项目(40473014;40221301)的资助

摘　　要：江西宜春黄玉-锂云母花岗岩是著名的稀有金属花岗岩,P_2O_5含量较高(平均0.56%)。该花岗岩全岩 Be 含量一般超过100×10^(-6),最高可达720×10^(-6),属于铍矿化花岗岩。本文利用电子探针技术对宜春铍矿化花岗岩中的铍磷酸盐及其共生矿物进行了系统研究。研究发现羟磷铍钙石是该花岗岩中的最重要铍矿物(BeO=15%～16%),偶尔亦可见磷钠铍石,它们主要呈晶间副矿物出现在岩体的中部。与铍矿物共生的矿物仍主要为磷酸盐矿物,如氟磷灰石、磷铝锂石、磷铝钠石,表明铍矿化作用与熔体中磷的聚集作用有显著关系。研究认为,宜春黄玉-锂云母花岗岩中铍以磷酸盐矿物形式结晶,而不是硅酸盐矿物,其主要原因可能为该花岗岩的结晶晚期磷的活度远远高于硅的活度,因此,P 优先作为成网离子与铍结合形成铍磷酸盐矿物。The famous Yichun topaz-leipidolite granite is characterized by its high P2 O5 contents of average 0.56%. Its whole-rock Be contents are generally higher than 100 × 10^-6, the highest reaches 720 × 10^ -6 indicating this granite belongs to the Be-mineralized granite. Systematic electron-microprobe study was carried out on the beryllophosphates and other associated phosphate minerals in the Yichun topaz-lepidolite granite. Beryllium minerals in the granite include mostly hydroherderite （ BeO = 15% - 16% ）, and rarely beryllonite, which appear as intergranular accessory minerals in the middle facies of the granite. Coexisting phosphates include fluorapatite, amblygonite and brazilianite, indicating that Be mineralization took place in P2Os-saturated melt. Therefore, it is suggested that beryllium speciation as phosphate rather than silicate in the Yichun granite is mainly controlled by relatively higher activity of P than that of Si during the crystallization course of this F-rich, peraluminous and perphosphorus granite. Phosphorus is favorable as network-forming cation to combine with Be, inducing crystallization of herderite or beryllonite if Be is available.

关 键 词：羟磷铍钙石 磷钠铍石 磷酸盐 富磷花岗岩 宜春黄玉-锂云母花岗岩 

分 类 号：P578.92[天文地球—矿物学]