Metamict gadolinite–(Y) from Ratnapura, Sri Lanka

Author(s): Lutz Nasdala, Christoph Hauzenberger, Manfred Wildner, Chutimun Chanmuang N., K. A. Geeth Sameera
Abstract: A fairly large (ca. 15 cm), massive glassy specimen of nearly black bulk colour, found in Ratnapura district, was identified as metamict gadolinite–(Y) based on its chemical composition Y_1.4Ln_0.6Ca_0.1Fe_0.9Be₂Si₂O₁₀ (with Ln = lanthanide elements La–Lu) and since the material reconstituted to monoclinic gadolinite–(Y) after two days of dry annealing in air at 1150 °C. Thin slabs (< 0.5 mm) of the specimen are bottle-green and transparent. Apart from surface weathering and small inclusions, the material is fairly homogeneous and does not show any indication of chemical alteration. Concentrations of Th (6310 ppm) and U (3360 ppm) in the material, and its calculated time-integrated alpha dose of ca. 8.5 × 10¹⁸ g^–1 based on the ²⁰⁶Pb/²³⁸U age of ca. 518 Ma, explain the present glassy state as being caused by radioactive self-irradiation over geological periods of time.
Organisation(s): Department of Mineralogy and Crystallography
External organisation(s): Karl-Franzens-Universität Graz, The Open University of Sri Lanka
Journal: Journal of the Geological Society of Sri Lanka
Volume: 24
Pages: 23-30
No. of pages: 8
ISSN: 2719-2326
Publication date: 10-2023
Peer reviewed: Yes
Austrian Fields of Science 2012: 104026 Spectroscopy, 105116 Mineralogy, 105113 Crystallography
Keywords
Portal url: https://ucrisportal.univie.ac.at/en/publications/a7260e57-1961-434d-8e5b-02c93f3bfaaf

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