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Geochemistry and provenance of the Turquoise Bluff Slate, northeastern Tasmania: tectonic significance


Berry, RF and Goemann, K and Thompson, J and Meffre, S and Bottrill, R, Geochemistry and provenance of the Turquoise Bluff Slate, northeastern Tasmania: tectonic significance, Australian Journal of Earth Sciences, 66, (2) pp. 227-246. ISSN 0812-0099 (2019) [Refereed Article]

Copyright Statement

Copyright 2018 Geological Society of Australia

DOI: doi:10.1080/08120099.2019.1541253


The Ordovician Turquoise Bluff Slate in northeastern Tasmania is a 2 km-thick sequence of deep-marine siliceous black slates. It is dominated by meta-siltstones with bimodal grainsize distributions typical of turbidite TE-1 and TE-2 facies. The slates have high SiO2 indicating they are hemipelagites. The high Ba and V indicate they were deposited in an anoxic environment associated with high oceanic productivity. All these features are common in muddy turbidites. UThPb dating of detrital monazite and authigenic xenotime in the slates supports previous evidence that the dominant cleavage, in this unit, formed during the Benambran Orogeny. The whole-rock composition of the slates is similar to black slates in the Adaminaby Group, NSW. A review of Paleozoic whole-rock compositions from the Lachlan Orogen confirms they all have trace element contents similar to average Australian shale. However, there are subtle differences in composition. The Turquoise Bluff Slate and other Mathinna Supergroup rocks from the Eastern Tasmania Terrane have higher average Cr content than similar age turbidites from Victoria and NSW. This probably reflects a small contribution from Tasmania Cambrian ultramafic rocks in the provenance. If this were correct, northeastern Tasmania was closer to western Tasmania in the Paleozoic than other provinces of the Lachlan Orogen, southeastern Australia. Other subtle features of the whole-rock composition of Paleozoic sedimentary rocks from the Lachlan Orogen indicate it may be possible to recognise provincial variations in composition that will provide new constraints on tectonic models of southeastern Australia.

Item Details

Item Type:Refereed Article
Keywords:Tasmania, Mathinna Supergroup, Benambran Orogeny, xenotime, whole-rock geochemistry, hemipelagic, muddy turbidite
Research Division:Earth Sciences
Research Group:Geology
Research Field:Structural geology and tectonics
Objective Division:Expanding Knowledge
Objective Group:Expanding knowledge
Objective Field:Expanding knowledge in the earth sciences
UTAS Author:Berry, RF (Associate Professor Ron Berry)
UTAS Author:Goemann, K (Dr Karsten Goemann)
UTAS Author:Thompson, J (Mr Jay Thompson)
UTAS Author:Meffre, S (Dr Sebastien Meffre)
ID Code:129972
Year Published:2019 (online first 2018)
Funding Support:Australian Research Council (LP160100483)
Web of Science® Times Cited:5
Deposited By:CODES ARC
Deposited On:2019-01-02
Last Modified:2019-03-12

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