四川冕宁氟碳铈矿晶体的成分变化及其意义  

Compositional Variations and Its Implications of a Bastnaesite Crystal,Mianning County, Sichuan Province

作　　者：吴澄宇[1] 袁忠信[1] 白鸽[1] 安庆骧[1] 王锐兵[1] 邓赛文[1] 

机构地区：[1]中国地质科学院矿床地质研究所,中国地质科学院岩石矿物分析测试研究所

出　　处：《中国稀土学报》1996年第1期1-5,共5页Journal of the Chinese Society of Rare Earths

摘　　要：对采自四川省冕宁县牦牛坪稀土矿床中伟晶状霓辉石－重晶石－氟碳铈矿脉的一个氟碳铈矿晶体（约１２×１２ｍｍ）在ＢＥＰＣ国家实验室采用同步辐射Ｘ萤光（ＳＲＸＲＦ）技术分析了Ｌａ、Ｃｅ、Ｐｒ和Ｎｄ。结果表明沿着晶体的纵、横剖面存在着明显的成分变化，可以划分为Ａ、Ｂ、Ｃ三个成分带。在晶体的内部带（Ａ区）和外部带（Ｂ区）之间存在着显著的成分差异。Ｌａ２Ｏ０３、ＣｅＯ２、Ｐｒ６Ｏ１１和Ｎｄ２Ｏ３的含量在Ａ区平均为２８．３５％、３５．０４％、２．０１％和５．４４％；而在Ｂ区平均为３２．８１％、４２．２６％、３．３０％和７．０８％；晶体边缘的Ｃ区仅获得一个分析数据，相应的含量依次为１４．５０％、２１．４１％、４．１９％和１６．７１％，表明ＬＲＥＥ和ＨＲＥＥ之间可能有分馏作用。然而在这三个带之间Ｌａ／Ｃｅ比值几乎是恒定的，约为０．８４±０．０８；而Ｌａ／Ｐｒ和Ｌａ／Ｎｄ比值则是跳跃性波动，其原因在于Ｐｒ和Ｎｄ的含量低且变化大。上述结果表明在氟碳铈矿晶体阶段性的生长过程中含ＲＥＥ热液系统经历了成分的变化。bastnaesite crystal about 12×20 mm in size collected from a pegmatitic aegirine augitebarite-bastnaesite vein of the Maoniuping rare earth deposit, Mianning County, Sichuan Province,has been analyzed for La, Ce, Pr and Nd by synchronous radiative X-ray fluorescence(SRXRF) technics at the National BEPC Laboratory. The results show an apparent compositional variation a long vertical and horizontal sections accross the crystal which may be divided into three compositional zones(A, B and C). Significant difference exists between the inner portion(zone A), averaging at 28. 35% La_2O_3 , 35. 04% CeO_2 , 2. 01% Pr_6O_(11) and 5.44 % Pr_2O_3, and the outer portion(zone B) , averaging at 32. 81% La_2O_3, 42. 26% CeO_2, 3. 30% Pr_6O_(11) and 7. 08% Pr_2O_3, of the crystal. Only one analysis is available on the egde of the crystal (zone C) yielding 14. 50% La_2O_3,21.41% CeO_2, 4.19% Pr_6O11 and 16.61% Pr_2O_3, which demonstrates probably fractionations between LREE and HREE. The La/Ce ratio, however, is nearly constanat around 0. 84 ±0. 08 among the three zones, while the La/Pr and La/Nd rations erratically fluctuate due to low and variable contents of Pr and Nd. These results indicate that the REE-bearing hydrothermal system underwent a significant compositional change during the stepwise growth of the bastnaesite crystal.

关 键 词：氟碳铈矿 晶体化学 稀土矿床 结晶 化学成分 

分 类 号：P618.920.4[天文地球—矿床学]