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The geochronology of Tasmanian tin deposits using LA-ICP-MS U-Pb cassiterite dating

Denholm, JL, Stepanov, AS, Meffre, S ORCID: 0000-0003-2741-6076, Bottrill, RS and Thompson, JM 2021 , 'The geochronology of Tasmanian tin deposits using LA-ICP-MS U-Pb cassiterite dating' , Economic Geology and The Bulletin of The Society of Economic Geologists , pp. 1-22 , doi: 10.5382/econgeo.4837.

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Abstract

The island state of Tasmania is the most important tin producer in Australia. The spatial and genetic relationship between Tasmanian tin deposits and Devonian-Carboniferous granites, which intruded throughout the Tabberabberan orogeny, has long been understood. However, little geochronological data is available to link mineralization to nearby intrusions. In this study, we investigate the connection between 19 Tasmanian tin deposits and their potential source granites, using U-Pb cassiterite dating by laser ablation-inductively coupled plasma-mass spectrometry. Archean pegmatitic cassiterite was also characterized and used for the calibration of U-Pb ratios.Tin mineralization in Tasmania occurred between 391 ± 6.3 and 359 ± 7.8 Ma, which is coincident with most postorogenic granites of the Tabberabberan orogeny. In conjunction with the granite ages, cassiterite ages become younger from the east of the state to the west, and tin mineralization occurred over a protracted period spanning 32 m.y. Dating of several placer cassiterite samples produced unexpected results, such as the occurrence of 374 ± 4.7 Ma cassiterite on eastern King Island, an area known only to contain the 350 Ma Grassy granite, suggesting a distant provenance.Tasmanian cassiterite rarely shows evidence of Pb loss; however, some analyses are characterized by elevated Th and U, likely caused by microinclusions such as monazite, which may have a detrimental effect on cassiterite U-Pb dating. This study demonstrates the utility of cassiterite dating for understanding the origin of tin deposits in complex terrains with protracted periods of tin mineralization.

Item Type: Article
Authors/Creators:Denholm, JL and Stepanov, AS and Meffre, S and Bottrill, RS and Thompson, JM
Journal or Publication Title: Economic Geology and The Bulletin of The Society of Economic Geologists
Publisher: Economic Geology Publ Co
ISSN: 0361-0128
DOI / ID Number: 10.5382/econgeo.4837
Copyright Information:

Copyright 2021 2021 Society of Economic Geologists, Inc.

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