期刊
MINERALOGICAL MAGAZINE
卷 77, 期 6, 页码 2857-2866出版社
MINERALOGICAL SOC
DOI: 10.1180/minmag.2013.077.6.11
关键词
irinarassite; garnet supergroup; Sn; EBSD; Raman; tazheranite; metasomatic rocks; Upper-Chegem Caldera
类别
资金
- Ministry of Science and Higher Education of Poland [N307 097038]
Irinarassite, Ca3Sn2SiAl2O12, a new mineral species of the garnet supergroup was discovered in metasomatically altered carbonate-silicate xenoliths in ignimbrites of the Upper Chegem Caldera, Northern Caucasus, Kabardino-Balkaria, Russia. It occurs as small zones and irregular spots in kimzeyite-kerimasite or rarely as single crystals not exceeding 10 mu m in size, within complex pseudomorphs after zircon. Lakargiite, tazheranite, baddeleyite, kerimasite, kimzeyite, baghdadite and rarely magnesioferrite are associated with irinarassite in the pseudomorphs which are confined to larnite-cuspidine zones immediately adjoining the ignimbrite. Larnite, cuspidine, rondorfite, fluor- and hydroxylellestadite, fluorite and secondary minerals such as ettringite, hillebrandite and bultfonteinite are associated with irinarassite. Irinarassite is pale brown to yellow colour. The mineral is characterized by the absence of cleavage and by an irregular fracture. The calculated density is 4.3 g cm(-1). The mineral is isotropic with a calculated refractive index of 1.9. The empirical crystal chemical formula of irinarassite from the holotype specimen is as follows (Ca2.965Fe0.0352+)(Sigma 3) (Sn(1.016)Zr(0.410)Ti(0.262)Sb(0.237)(5+)Fe0.352+U0.0176+Sc0.014Hf0.006Nb0.004)(Sigma 2.001)(Al1.386F0.8043+Si0.446Ti0.3644+)(Sigma 3)O-12. Electron backscatter diffraction patterns of irinarassite are fitted to the garnet model with a = 12.50(3) angstrom with excellent MAD (mean angular deviation) = 0.16 degrees. The Raman spectrum of irinarassite is analogous to those of kerimasite and other Zr-Sn-garnets of the schorlomite and bitikleite groups.
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