Tourmaline in a complex type granitic pegmatite of an Li-Cs-Ta enriched (LCT) family from Nagatare pegmatite, Fukuoka Prefecture, Japan, were classified into five types: type-A (black), type-B (indigo), type-C (light blue-pink), type-D (pink), and type-E (pink-light blue), on the basis of localities, associated minerals, color, and texture. Type-C shows color zoning textures of a light blue core and a pink rim. In contrast, type-E has a pink core and a light blue rim. A total of 29 samples were analyzed by an electron microprobe analyzer (EPMA) and an X-ray diffractometer (XRD). Significant substitution of (Li + Al) for Fe is observed at the Y sites. The minor cations at the Y site, such as Mg, Mn, Zn and Ti, were also characteristic on each type. Large amounts of Na were detected at the X site in type-B; the Na contents decreased with increasing (Li + Al) in types-C, D, and E. F contents were well correlated with X-site charge except in type-A. The mineral species from the Nagatare pegmatite were schorl, fluor-schorl, elbaite, fluor-elbaite, and rossmanite. The unit-cell parameters were in the range of rossmanite, elbaite, and schorl. The tourmaline from the Nagatare pegmatite has similar major chemical components but different minor elements such as Zn and Mn as compared to the tourmaline from other LCT pegmatites. The intermediate fractionated tourmaline containing Zn (0.00-0.20 apfu) and Mn (0.11-0.38 apfu) is characteristic of the Nagatare pegmatite. In type-E, the rim showed greater Fe and Mn contents than the core, differing from the trend of the melt development on types-B and C. Furthermore, the parts rich in Al, Li, and OH with considerable site vacancy were selectively replaced by muscovite. These features indicate that several stages of alterations occurred during the late stages of the pegmatite formation.
|Number of pages||6|
|Journal||Journal of Mineralogical and Petrological Sciences|
|Publication status||Published - 2013|
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