Journal of Geography (Chigaku Zasshi)
Online ISSN : 1884-0884
Print ISSN : 0022-135X
ISSN-L : 0022-135X
Original Articles
Dalyite (K2ZrSi6O15) and Zektzerite (LiNaZrSi6O15) in Aegirine-bearing Albitite from Iwagi Islet, SW Japan
Teruyoshi IMAOKASachiho AKITAMariko NAGASHIMA
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2021 Volume 130 Issue 3 Pages 369-378

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Abstract

 The rare potassium zirconium silicate dalyite and lithium sodium zirconium silicate zektzerite have been found in Cretaceous aegirine albitite from Iwagi Islet, Southwest Japan. Electron microprobe analyses of the dalyite and zektzerite yielded the following empirical formulas based on 15 oxygens: (K1.93Ba0.01)Σ1.94(Zr0.99Hf0.02)Σ1.01Si5.98O15 and Na1.03(Zr0.96Hf0.02Y0.01Sc0.01)Σ1.00Li1.02(Si5.95Al0.04)Σ5.99O15, respectively. The occurrence of porous zircon, dalyite, and mantles of zektzerite on resorbed zircon in the albitite suggests that those zirconosilicate minerals are the products of metasomatic mineral replacement reactions by Na-, K-, and Li-rich hydrothermal fluids. This is the first documented occurrence of dalyite and zektzerite in the Japanese Islands.

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