新疆拜城波孜果尔碱性岩中副矿物的特征

Radioactive mineral characteristics of Boziguoer alkaline rocks in Baicheng,Xinjiang

在野外地质调查的基础上,结合室内显微镜观察及电子探针分析测试,对新疆拜城波孜果尔碱性岩中的副矿物的矿物学特征和化学成分进行了研究。发现这些副矿物常以共生组合的形式产在碱性岩中,主要分布在石英二长闪长岩和石英二长岩中。烧绿石中U、Th和REE替代Ca、Na。独居石富含LREE,Th和LREE相互替代;根据独居石中w(La+Ce)>40%和La/Nd比值在1·6～4·5,推断独居石为热液成因。磷钇矿中富含REE,且以HREE为主;w(Th)>w(U)。锆石中Zr/Hf比值在60%以上,符合碱性岩特征;其Th/U比值为0·6,属于岩浆锆石。星叶石中w(Rb2O)、w(Cs2O)较高。萤石中Y、Ce替代Ca。锆石中的钍石w(U)明显高于磁铁矿中钍石w(U)。在石英二长岩中,烧绿石的w(CaO)、w(TiO2)、w(ZrO2)、w(U3O8),磷钇矿的w(Y2O3),星叶石的w(TiO2),萤石的w(Ca),氟碳铈镧矿的w(CaO)较丰富;而在石英二长闪长岩中,烧绿石的w(Ce2O3),磷钇矿的REE含量,星叶石的w(Nb2O5)、w(Rb2O),萤石w(Ce)、w(Y)和氟碳铈镧矿的w(La2O3)较高。

Trace elements, REE and radioactive mineral characteristics and chemical composition of Boziuoer alkali granite in Baicheng of Xinjiang were studied by means of field survey, microscopic observation and electron microprobe analysis （EPMA）. Trace elements, REE and radioactive ores are distributed in alkali rocks, especially in quartz-diorites and quartz monzonite, Ca, Na are replaced by U, Th, and Nb is replaced by Ti in pyrochlore. Monazite is rich in LREE, Th, and LREE are replaced by each other. According to the data that La＋Ce〉40% and the ratio of La/Nd is between 1.6 and 4.5, the authors infer that the monazite is related to the hydrothermal activity. Xenotime is rich in REE, mainly HREE. The content of Th is higher than that of U. The Zr/Hf ratio is higher than 60%, which is consistent with features of alkaline granite. The ratio of Th/U is 0.6, Th/U〉0.4, suggesting that the zircons belong to magmatic type. Rb2O and Cs2O are concentrated in astrophyllite. Ca is replaced by Y and Ce in fluorite. The content of U of thorite distributed in zircon is higher than that of thorite distributed in magnetite. In quartz monzonite, CaO, TiO2, ZrO2, U3O8 in pyrochlore, Y2O3 in xenotime, TiO2 in astrophyllite, Ca in fluorite and CaO in bastnaesite are comparatively high in content. In quartz-diorites, Ce2O3 in pyrochlore, REE in xenotime, Nb2O5,Rb2O in astrophyllite, Ce,Y in fluorite and La2O3 in bastnaesite are also relatively high in content.