The crystal structure of a fluorine-dominant titanium calcium amphibole from the Eifel paleovolcanic area, Germanyстатья
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Дата последнего поиска статьи во внешних источниках: 24 октября 2016 г.
Аннотация:A new fluorine-dominant titanium calcium amphibole (FTCA) was found in alkali basalts of the Roth-enberg volcano situated in the Eifel paleovolcanic region, Rhineland-Palatinate (Rheinland-Pfalz), Germany. The empirical formula based on 24 (O + F) atoms is (Na0.65K0.30) (Ca Na-1.95(0.05))(Mg3.36Fe03+ .87Fe0.132+Ti (0.60))(Si5.92Al2.08)O-22 (F1.11O0.89). The crystal structure has been studied based on single-crystal X-ray diffraction data. The monoclinic unitcell parameters are: a = 9.8684(2) angstrom, b = 18.0457(3) angstrom, c = 5.3113(1) angstrom, beta = 105.543(3)degrees; space group C2/m. The structure was refined to R = 3.39% in anisotropic approximation using 3661F > 4 sigma F. The studied mineral is the first representative of F-dominant amphiboles with Ti-C > 0.5. It is considered as a F-dominant analogue of ferri-kaersutite NaCa2 [Mg3Fe3+Ti](Si6Al2O22 )O-2.