• journal_title：European Journal of Mineralogy
• Contributor：Zhuming YANG ; Michel FLECK ; Martin SMITH ; Kejie TAO ; Renkui SONG ; Peishan ZHANG
• Publisher：E. Schweizerbart'sche Verlagsbuchhandlung Science Publishers
• Date：2002-
• Format：text/html
• Language：en
• Identifier：10.1127/0935-1221/2002/0014-0969
• journal_abbrev：Eur J Mineral
• issn：0935-1221
• volume：14
• issue：5
• firstpage：969
• section：Articles

Chemical composition and crystal structure of natural non-metamict Fe-rich chevkinite-(Ce) from the aegirine-alkali granite, Mianning, Sichuan Province, China, were investigated. Microprobe analyses indicated that FeO (total iron) content in Fe-rich chevkinite(Ce) ranges from 10.97 % to 11.59 % (wt.) and Ce₂O₃ from 23 % to 25 %. There are deficient A- and (B+C)-type cations in the formula. The crystal structure of Fe-rich chevkinite-(Ce) was refined from CCD data in the space-group type C2/m (R = 2.41 %). Cell parameters are a = 13.456(3) Å, b = 5.728(1) Å, c = 11.083(2) Å, β = 100.60(3)°, V= 839.7(3) ų, Z = 2. The structure of Fe-rich chevkinite-(Ce) is made up of two kinds of sheets, one is a sheet of Si₂O₇ groups and B-octahedra, and the other is a sheet of C-octahedra, both parallel to the ab plane. The two kinds of sheets alternate along c axis and form a three dimensional framework. The rare earth ions lie between the disilicate groups and the sheets of octahedra to form (8+3)-coordinated A1-polyhedra and 10-coordinated A2-polyhedra. The Fe and Ti are partially ordered among the octahedral sites of B, C1, C2A and C2B. The Charge Distribution analysis confirms Fe₃₊/ΣFe = 0.61 and a mixture of Fe²⁺ and Fe³⁺ in the B site. The chemical formula for the natural Fe-rich chevkinite-(Ce) is (Ce³⁺_1.76La_0.89Ca_0.46Nd_0.22Pr_0.18Sm_0.04Gd_0.04Th_0.03Ba_0.01□_0.37)Σ_4.00(Fe³⁺_0.29Ti_0.21Fe²⁺_0.18Mn²⁺_0.13Mg_0.18□_0.11)_Σ1.00(Ti_2.16Fe³⁺_0.81Fe²⁺_0.52Nb_0.16Al_0.06□_0.08)_Σ4.00Si₄O_20.72(OH)_1.28..