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A review of molybdenite, and fluorite mineralization in Caledonian granite basement, western Ireland, incorporating new field and fluid inclusion studies, and Re-Os and U-Pb geochronology

Feely, Martin; Costanzo, Alessandra; Gaynor, Sean P.; Selby, David; McNulty, Emma

A review of molybdenite, and fluorite mineralization in Caledonian granite basement, western Ireland, incorporating new field and fluid inclusion studies, and Re-Os and U-Pb geochronology Thumbnail


Authors

Martin Feely

Alessandra Costanzo

Sean P. Gaynor

Emma McNulty



Abstract

The recent discovery of late-magmatic quartz vein hosted molybdenite, and exceptional gem quality vein fluorite, in the Caledonian Galway Granite Complex (GGC), has prompted a review of these contrasting styles of mineralisation in the late-Caledonian granite basement, Connemara, western Ireland. Existing published U-Pb and Re-Os chronometry and fluid inclusion microthermometry are combined with new: a) geological field observations, b) U-Pb zircon and Re-Os molybdenite geochronometry and c) fluid inclusion microthermometry to generate a new pressure-temperature-time model (P-T-t) of mineralization for the GGC. Re-Os chronometry molybdenite indicates that granite related molybdenite mineralisation extended from 423 to 380Ma overlapping with the GGC emplacement history determined by U-Pb zircon chronometry. The P-T-t model reflects initial granite emplacement and Mo-mineralisation at ∼423Ma followed by lower P and T granite emplacement and related quartz vein hosted Mo-mineralisation at ∼410Ma (Carna pluton), ∼400Ma (Kilkieran pluton) and at ∼380Ma (Costelloe Murvey granite). The gem quality fluorite veins in the GGC represent late-Triassic hydrothermal mineralisation. These veins form part of a regional N Atlantic-European Triassic-Jurassic hydrothermal mineralisation province. Vein emplacement was triggered by the rifting of the N Atlantic facilitating crustal thinning and subsidence of continental crust and initiating hydrothermal activity at the margins of Mesozoic basins.

Citation

Feely, M., Costanzo, A., Gaynor, S. P., Selby, D., & McNulty, E. (2020). A review of molybdenite, and fluorite mineralization in Caledonian granite basement, western Ireland, incorporating new field and fluid inclusion studies, and Re-Os and U-Pb geochronology. Lithos, 354-355, Article 105267. https://doi.org/10.1016/j.lithos.2019.105267

Journal Article Type Article
Acceptance Date Oct 28, 2019
Online Publication Date Nov 9, 2019
Publication Date Feb 28, 2020
Deposit Date Nov 15, 2019
Publicly Available Date Mar 29, 2024
Journal Lithos
Print ISSN 0024-4937
Publisher Elsevier
Peer Reviewed Peer Reviewed
Volume 354-355
Article Number 105267
DOI https://doi.org/10.1016/j.lithos.2019.105267

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