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B- and O-isotopic compositions of tourmaline constrain late-stage magmatic volatile exsolution in Tasmanian tin-related granite systems

Citation

Hong, W and Fox, N and Cooke, DR and Zhang, LJ and Fayek, M, B- and O-isotopic compositions of tourmaline constrain late-stage magmatic volatile exsolution in Tasmanian tin-related granite systems, Mineralium Deposita, 55, (1) pp. 63-78. ISSN 0026-4598 (2020) [Refereed Article]

Copyright Statement

Copyright Springer-Verlag GmbH Germany, part of Springer Nature 2019

DOI: doi:10.1007/s00126-019-00885-5

Abstract

The Devonian Sn-mineralized Heemskirk and barren Pieman Heads granites of western Tasmania (southeast Australia) contain abundant tourmaline-rich features, including orbicules, patches, cavities, and veins within their roof zones. The δ11B and δ18O compositions of tourmaline from these texturally different features range from − 21.7 to + 4.1 (average − 4.7  4.0, n = 127), and from + 6.5 to + 14.9 (average + 10.7  1.8, n = 38), respectively. These data suggest that the tourmaline-rich assemblages precipitated mostly from magmatic-hydrothermal fluids derived from their host plutons, mixed with minor external components sourced from metasedimentary, meta-ultramafic rocks, and/or meteoric water. The B-isotopic values increase sequentially from tourmaline patches to orbicules and/or cavities in both granites, probably caused by progressive volatile exsolution and systematic fluxing of aqueous boron-rich fluids from the S-type magmas during emplacement into the shallow crust. High degrees of fractional crystallization of the melt may have caused the exsolution of boron-rich hypersaline fluids from which the tourmaline orbicules and cavities formed. Bimodal δ11B populations (− 21.7 to − 12.7 and − 3.9 to + 4.0) imply that the granitic melts were mostly sourced from 10B-rich metapelitic rocks. The granites underwent fluid exsolution during the late magmatic stage that contributed to the widespread development of tourmaline-rich features and also to the formation of tin deposits associated with the Heemskirk Granite.

Item Details

Item Type:Refereed Article
Keywords:B- and O-isotopes, tourmaline , volatile exsolution, tin mineralization, Tasmania
Research Division:Earth Sciences
Research Group:Geochemistry
Research Field:Isotope Geochemistry
Objective Division:Mineral Resources (excl. Energy Resources)
Objective Group:Mineral Exploration
Objective Field:Mineral Exploration not elsewhere classified
UTAS Author:Hong, W (Mr Wei Hong)
UTAS Author:Fox, N (Dr Nathan Fox)
UTAS Author:Cooke, DR (Professor David Cooke)
UTAS Author:Zhang, LJ (Dr Lejun Zhang)
ID Code:136562
Year Published:2020 (online first 2019)
Funding Support:Australian Research Council (IH130200004)
Deposited By:CODES ARC
Deposited On:2020-01-08
Last Modified:2020-05-01
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