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The geochronology of Tasmanian tin deposits using LA-ICP-MS U-Pb cassiterite dating
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.
Funding
Australian Research Council
Alkane Exploration NL
AngloGold Ashanti Australia Limited
CMOC Mining Services Pty Ltd T/A Northparkes Mines
Department of Economic Development, Jobs, Transport and Resources
Department of State Growth (Tas)
Emmerson Resources Limited
Evolution Mining
Geological Survey of New South Wales - Department of Industry
Geoscience Australia
Heron Resources Limited
New South Resources Limited
Rio Tinto Limited
Sandfire Resoures NL
History
Publication title
Economic Geology and The Bulletin of The Society of Economic GeologistsPagination
1-22ISSN
0361-0128Department/School
School of Natural SciencesPublisher
Economic Geology Publ CoPlace of publication
5808 South Rapp St, Ste 209, Littleton, USA, Co, 80120-1942Rights statement
Copyright 2021 2021 Society of Economic Geologists, Inc.Repository Status
- Restricted