Original paper

Chevkinite in syenites from Cape Ashizuri, Shikoku Island, Japan

Imaoka, Teruyoshi; Nakashima, Kazuo

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Neues Jahrbuch für Mineralogie - Monatshefte Jg. 1994 Heft 8 (1994), p. 358 - 366

28 references

published: Aug 16, 1994

DOI: 10.1127/njmm/1994/1994/358

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ArtNo. ESP156199408002, Price: 19.00 €

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Abstract

Chevkinite has been found in Miocene syenites of Cape Ashizuri, Shikoku Island, Southwest Japan. The non-metamict crystallinity of this mineral gives definitive X-ray data on unheated material. The unit cell parameters obtained are a = 13.461(26), b = 5.676(9), c = 11.352(14)Å, ß = 100.86(10)°, which give a cell volume of 851.8 Å3. For Z = 2, Dcalc = 4.88 g/cm3. Electron microprobe analyses of chevkinite show little variation in composition within and among grains and yield the following empirical formula based on 22 oxygens: (Ce1.685La1.005Ca.694Nd.298 Th.229Y.061Eu.016Dy.012) 𝛴4.00(Ti2.402Fe2.068Nb.381Mg.090Ca.065, Mn.041)𝛴5.05Si4.07O22. The mineral is notably enriched in LREEs, Nb and Th. This is the first reported occurrence of chevkinite in Japan.

Keywords

Chevkinite • A-type granite • syenite • X-ray diffraction • EPMA • Japan