- 著者
- Yasuyuki BANNO Koichi MOMMA Ritsuro MIYAWAKI Michiaki BUNNO
- 出版者
- Japan Association of Mineralogical Sciences
- 雑誌
- Journal of Mineralogical and Petrological Sciences (ISSN:13456296)
- 巻号頁・発行日
- pp.220724, (Released:2023-02-04)
Katoite, ideally denoted as {Ca3}[Al2](□xSi3-x)(OH)4xO12-4x, where 1.5 < x ≤ 3, was found in skarn xenoliths from Tadano, Fukushima Prefecture, Japan, and investigated by electron microprobe analyses, X-ray single crystal structure refinement, and infrared (IR) spectroscopy. Katoite characteristically contains up to 0.18 atoms per formula unit (apfu) of S and has a range of compositions, wherein Si = 0.96-1.25 apfu, Al = 1.47-1.74 apfu, Fe = 0.13-0.28 apfu, and Mg = 0.01-0.10 apfu. A difference Fourier map revealed the residual electron density near the octahedral Y site (Wyckoff position = 16a), and we interpreted that S with three-fold coordination occurs at the position of the residual electron density, which is represented as the Y’ site (Wyckoff position = 32e). The final refinement introduced the Y’ site to yield R1 [F2 > 2σ(F2)] = 0.0353 with space group Ia3d and unit cell parameter a = 12.24095(8) Å. The IR spectrum in the range of 800-1200 cm-1 shows a band at 1124 cm-1 due to ν3(SO4) and doublet bands at 879 and 931 cm-1 with different absorbances interpreted as ν3(SiO4) overlapping with ν3(SO3). The combined results of IR spectroscopy and structure refinement imply that in the Tadano katoite, S4+ and S6+, forming (SO3)2- and (SO4)2- coordinations, are placed at the Y’ and tetrahedral Z sites, respectively. Assuming that S is preferentially allotted to the Y’ site as S4+ to compensate for the deficiency of the octahedral cations Al, Fe, Mg, Mn, and Ti at the Y site, chemical formulae, including possible S4+ and S6+ contents, may be calculated. The average chemical formula for 14 different spots is as follows: {Ca3}[(Al1.614Fe3+0.208Mg0.063Ti0.019)Σ1.90S4+0.096]Σ2.00(□1.867Si1.120S6+0.013)Σ3.00[(OH)7.192O4.612F0.147Cl0.048]Σ12.00.
- 著者
- Yasuyuki BANNO Koichi MOMMA Ritsuro MIYAWAKI Shigeo YAMADA
- 出版者
- Japan Association of Mineralogical Sciences
- 雑誌
- Journal of Mineralogical and Petrological Sciences (ISSN:13456296)
- 巻号頁・発行日
- vol.114, no.1, pp.33-40, 2019 (Released:2019-03-08)
- 参考文献数
- 20
Chemically heterogeneous amphibole, ranging in composition from magnesio–riebeckite through ferri–ghoseite to clino–suenoite, was found in a specimen of Sanbagawa quartz schist from the Iimori region of the western Kii Peninsula, central Japan. The amphibole exhibits a continuous solid solution between BNa and BMn2+ (BMn2+ = 0–1.82 atoms per formula unit). Most of the amphibole crystals comprise a Mn–poor core and a Mn–rich rim, and ferri–ghoseite often occurs near the boundary between core and rim. The crystal structure of a single crystal fragment of ferri–ghoseite, which has an averaged composition of A(Na0.16K0.02)Σ0.18B(Na0.83Ca0.09Mn2+1.08)Σ2.00C(Mg3.78Mn2+0.52Fe3+0.66Al0.04)Σ5.00T(Si7.95Al0.05)Σ8.00O22W[(OH)1.90F0.10]Σ2.00 based on electron–microprobe analyses, was refined to a R1 of 6.7%, has unit cell parameters of a = 9.6389(7), b = 18.0534(10), c = 5.3138(3) Å, and β = 102.896(2)°, and is in space group C2/m with Z = 2. The site populations for B cations of the ferri–ghoseite are M4(Na0.83Ca0.09)M4’Mn2+1.08, which also confirms the B(Na,Mn2+) solid solution. Sector–zoned aegirine occurs in the amphibole–bearing quartz schist from Iimori, and it is assumed that most of the metamorphic minerals in the quartz schist formed under non–equilibrium conditions. Therefore, taking into account the miscibility gap between sodium amphibole and clino–suenoite, the solid solution between BNa and BMn2+ in the amphibole can be inferred to have resulted from rapid, non–equilibrium crystallization rather than high–T equilibrium crystallization.