氟铁云母的晶体结构分析

STRUCTURE SOLUTION FROM X-RAY POWDER DIFFRACTION DATA OF FLUOR-ANNITE

氟铁云母是三八面体云母类矿物新种,属铁云母的富氟类似物。利用电子探针、湿法和原子吸收分析等手段并结合穆斯堡尔谱分析的结果,按O+OH+F+Cl=12及四面体阳离子数之和为4计算的氟铁云母经验化学式为:(K0.92Na0.03Rb0.02Ba0.01)0.98(Fe1.822+Fe0.493+Al0.19Mg0.18Li0.16Ti0.08Mn0.05Zn0.02)2.99(Al1.17Si2.83)4.00O10(F1.03OH0.50O0.47)2.00。其理想化学式为:KFe32+AlSi3O10F2。使用粉晶XRD衍射仪,采用毛细管装样和超能探测器相结合收集衍射数据/图谱的微区衍射新方法收集氟铁云母的粉末衍射数据,通过构建晶体结构模型和Rietveld法晶体结构精修并收敛到Rp=2.51%,Rwp=3.19%,Rexp=2.85,χ2=1.253完成晶体结构解析。矿物属于单斜晶系1 M型,空间群C2/m;晶胞参数:a=0.537 05(4)nm,b=0.929 95(6)nm,c=1.017 35(6)nm;β=100.465(5)°,V=0.499 64(5)nm3;Z=2。

Fluor-annite is a new mineral of trioctahedral mica group,belonging to the F-rich analogue of annite. The crystal structure of fluor-annite has been solved by positive space method from constructed crystal structure model and subsequently refined with the Rietveld technique. The sample used for the structure solution comes from the fluor-annite differentiating at the top of the Suzhou A-type granite located in the western suburb of Suzhou City. The samples were filled in capillary tube and X-ray powder diffraction data were obtained with a super detector in X＇ Pert PRO diffractometer, Fluor-annite crystallizes in the monoelinic space group C2/m with unit cell parameters a=0. 537 05（4） nm,b=0. 929 95（6） nm, c=1.017 35（6） nm;β=100. 465（5）°,V =0. 499 64（5）nm^3 ;Z=2,and the mineral is 1 M polytype. The Rietveld refinement of the data set converged to Rp= 2. 51% , Rwp=3.19%, Rexp=2.85,Х^2=1.253, Chemical constituents are calculated by EPMA,wet analysis,atomic absorption spectrometry and mossbauer spectral analy- sis, and an empirical chemical formula is formulated on the basis of （O＋F＋OH＋Cl）= 12 and the assumption that the sum of tetrahedral cation equals 4 is （K0.92Na0.03Rb0.02Ba0.01）0.98（Fe1.82^2＋Fe0.49^3＋Al0.19Mg0.18Li0.16Ti0.08Mn0.05Zn0.02）2.99（Al1.17Si2.83）4.00O10（F1.03OH0.50O0.47）2.00 ,with the simplified formula being KFe3^2＋AlSi3O10F2.