黑云霓石碳酸岩中的黄菱锶铈矿

BURBANKITE IN BIOTITE-AEGIRINE CARBONATITE FROM HUBEI PROVINCE

产于湖北杀熊洞碳酸岩杂岩体的黑云霓石碳酸岩中的黄菱锶铈矿在国内属首次发现。它呈≤0.2mm细粒浸染状产出,与磷灰石、黄铁矿、磁铁矿、烧绿石等矿物伴生。黄菱锶铈矿呈浅红至淡黄褐色,具油脂光泽,条痕白色,实测比重3.501,No=1.6228,Ne=1.6124,一轴晶,负光性,晶胞参数为a=10.49A,c=6.42A。最强的X射线衍射峰值为2.62(100),3.026(60)和2.138(50)。最强的红外光谱峰为1500,1450和860cm^(-1)。在差热曲线上见有两个明显的吸热谷(633和727℃)。据其化学成分计算,其晶体化学式为:Ce_(0.10)Na_(0.26)Ca_(0.34)Ba_(0.04)Sr_(0.38))_(1.12)C_(0.98)O_3。其成因看来与寄主岩(黑云霓石碳酸岩)的成分和成岩条件有关。

Burbankite from biotite-aegirine carbonatite in the Shaxiongdong carbona-tite complex, Hubei Province, has been discovered in China for the first time.It occurs in the form of impregnation grains measuring about≤0.2mm, and isassociated with apatite, pyrite, magnetite and pyrochlore. Reddish topale yellow- brown, greasy luster, white streak, empirical sp. gr. 3.501,No=1.6228, Ne=1. 6124, uniaxial negative. Its chemical analysis gave: Na_2O 6.03%, CaO 14.52%, SrO 29.49%, BaO4.87%, REE_2O_3 12.53% and CO_2 32.58%. The empirical formula is (Ce_(0.10)Na_(0.26)Ca_(0.34)Ba_(0.04)Sr_(0.38))_(1.12)C_(0.98)O_3. The simplified formula can be written as(Ce, Na, Ca, Ba, Sr) CO_3 in conformity with the ideal formula defined bySiminf(1963). The ∑REE content of the burbankite determined by ICP is106993.15 ppm and the REE is predominated by LREE up to 98.96%. X-ray diffraction analysis shows that the cell parameters of the burbankiteare:α=10.49 A, and c=6.42 A. The strongest lines are: 2.620(100), 3. 026 (60)and 2.138(50). The most intense infrared absorption spectra appear at 1500,1450 and 860 cm^(-1). There are obviously two endothermic valleys (633℃ and 727℃) on the differential thermal curve. In addition, the genesis of the burbankite is also discussed in this paper.There is no hesitation in drawing the conclusion that the burbankite is geneti-cally connected with the forming conditions and chemical composition of itshost rock (biotite-aegirine carbonatite).