Dingdaohengite-(Ce) from the Bayan Obo REE-Nb-Fe Mine, China: Both a true polymorph of perrierite-(Ce) and a titanic analog at the C1 site of chevkinite subgroup

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	Dingdaohengite-(Ce) from the Bayan Obo REE-Nb-Fe Mine, China: Both a true polymorph of perrierite-(Ce) and a titanic analog at the C1 site of chevkinite subgroup
	Xu, JS (Xu, Jinsha); Yang, GM (Yang, Guaming); Li, GW (Li, Guowu); Wu, ZL (Wu, Zhilan); Shen, GF (Shen, Ganfu)
刊名	AMERICAN MINERALOGIST
	2008
卷号	93 期号:5-6 页码:740-744
关键词	dingdaohengite-(Ce) P2(1)/a (pseudo-C2/m) space group chevkinite subgroup new mineral Bayan Obo China
ISSN号	0003-004X
英文摘要	Dingdaohengite-(Ce), ideally Ce4Fe2+Ti2Ti2(Si2O7)(2)O-8, is a new member of the chevkinite group minerals from the world-famous Bayan Obo REE-Nb-Fe Mine near Baotou city, Inner Mongolian Autonomous Region, North China. It occurs in the magnesian skarn in the excontact of granite within dolomitic marble. Most individual crystals vary from 0.2 to 1.0 cm in length. Associated minerals are diopside, tremolite, richterite, allanite-(Ce), magnetite, ilmenite, spinet, titanite, pyrochlore, F-rich phlogopite, fluorapatite, quartz, and fluorite, etc. Dingdaohengite-(Ce) is probably of bimetasomatic origin among Ca-Mg-carbonate rock and/or carbonatite, and REE-, F-rich postmagmatic hydrothermal solutions. The mineral is black and becoming brown black in thin fragments. It is translucent to opaque with a submetallic-metallic luster, and a brown streak. It is brittle with conchoidal fracture. No cleavage or parting is observed. Its hardness is VHN(25)g 606.0-717.4 kg/mm(2) (Mohs hardness near 5.9). The measured density is 4.83(7) g/cm(3) and the calculated density is 4.88(0) g/cm(3). Its reflectance values (for lambda = 589 nm) are 11.4-12.5%. It is biaxial negative. The strongest six X-ray diffraction lines in the powder pattern [d in angstrom (I) (hkl)] are 2.7524(100)((1) over bar 21), 2.7263(98)(313), 3.1978(68)(212), 2.5460(54)((3) over bar 04), 2.8702(52)(020), and 3.1622(46)((3) over bar 12). An electron-microprobe analysis on the crystal used to collect X-ray intensity data for crystal-structure refinement gives SiO2 19.29, TiO2 18.26, Al2O3 0.04, FeO 8.49, Fe2O3 1.67, ThO2 0.16, MgO 1.32, CaO 2.17, Nb2O5 0.47, Ta2O5 0.00, La2O3 19.53, Ce2O3 28.08, Nd2O3 n.d., Y2O3 0.00, Na2O 0.00, sum 99.48 wt%; the Fe3+/Fe2+ ratio was converted by Mossbauer spectroscopy. The empirical formula is Ce2.13La1.49Ca0.48Th0.01)(Sigma 4.11)Fe2+(Ti0.88Fe0.472+Mg0.41Fe0.263+Al0.01)(Sigma 2.03)(Ti1.96Nb0.04)(Sigma 2.00)(Si2O7)(2)O-8, based on 22 atoms with prevalence of Ti in the C1 site of the structure. Dingdaohengite-(Ce) is monoclinic, a 13.4656(15) angstrom, b = 5.7356(6) angstrom, c = 11.0977(12) angstrom, beta = 100.636(2)degrees, V = 842.39(46) angstrom(3), and Z = 2. The crystal structure of dingdaohengite-(Ce) was refined with space groups P2(1)/a and C2/m. Pseudo-extinction was found, i.e., reflections with h + k = 2n are systematically strong, while those with h + k = 2n + 1 are weak, which show that the true space group of dingdaohengite-(Ce) is P2(1)/a (pseudo-C2/m).
学科主题	矿床地质
WOS关键词	CRYSTAL-STRUCTURE ; RICH
WOS研究方向	Geochemistry & Geophysics ; Mineralogy
语种	英语
出版者	MINERALOGICAL SOC AMER
WOS记录号	WOS:000256133500003
内容类型	期刊论文
源URL	[http://119.78.100.197/handle/2HKVOGP0/38621]
专题	中国地质调查局
作者单位	Bayan Obo Iron Mine, Technol Managerial Dept, Baotou 014080, Peoples R China
推荐引用方式 GB/T 7714	Xu, JS ,Yang, GM ,Li, GW ,et al. Dingdaohengite-(Ce) from the Bayan Obo REE-Nb-Fe Mine, China: Both a true polymorph of perrierite-(Ce) and a titanic analog at the C1 site of chevkinite subgroup[J]. AMERICAN MINERALOGIST,2008,93(5-6):740-744.
APA	Xu, JS ,Yang, GM ,Li, GW ,Wu, ZL ,&Shen, GF .(2008).Dingdaohengite-(Ce) from the Bayan Obo REE-Nb-Fe Mine, China: Both a true polymorph of perrierite-(Ce) and a titanic analog at the C1 site of chevkinite subgroup.AMERICAN MINERALOGIST,93(5-6),740-744.
MLA	Xu, JS ,et al."Dingdaohengite-(Ce) from the Bayan Obo REE-Nb-Fe Mine, China: Both a true polymorph of perrierite-(Ce) and a titanic analog at the C1 site of chevkinite subgroup".AMERICAN MINERALOGIST 93.5-6(2008):740-744.