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Mafic volcanic rocks on King Island, Tasmania: evidence for 579 Ma break-up in east Gondwana

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Meffre, S and Direen, NG and Crawford, AJ and Kamenetsky, VS (2004) Mafic volcanic rocks on King Island, Tasmania: evidence for 579 Ma break-up in east Gondwana. Precambrian Research, 135 (3). pp. 177-191.

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Abstract

The eastern coast of King Island in southeastern Australia exposes a thick, well-preserved sequence of latest Neoproterozoic volcanic, and related shallow intrusive rocks. These rocks are associated with shallow marine carbonates and siltstones and pass up into massive conglomerates representing a marine flooding event and unconformity, during continental break-up and subsequent volcanic passive margin formation. Unusual differentiated sills (Grimes Intrusive suite) with extreme internal variation (wehrlite to andesite compositions) intrude deformed Proterozoic metasediments of the Rodinian basement. A thin, basal tholeiitic basaltic volcanic unit (City of Melbourne Volcanics) is less contaminated than the underlying sills, and preceded eruption of a thick sequence of highly depleted picritic pillows, sub-aerial flows and hyaloclastites (Shower Droplet Volcanics). The picrite sequence is overlain by thick tholeiitic basalts and reworked volcanogenic conglomerates (Bold Head Formation) that show a strong compositional similarity to enriched mid ocean ridge basalts. Both the picrites and the upper tholeiitic basalts are not crustally contaminated and have an Nd-Sm isochron age of 579 +/- 16 Ma with initial epsilonNd of +4.2. The lithostratigraphy and range of compositions represented are analogous to early magmatism associated with continental break-up and volcanic passive margin formation, including voluminous Seaward Dipping Reflector Sequences, in the Mesozoic North Atlantic volcanic margins.

Item Type: Article
Keywords: continental break-up; crustal contamination; large igneous province; picrite; rodinia; tasmania; southeastern australia
Journal or Publication Title: Precambrian Research
Page Range: pp. 177-191
Identification Number - DOI: 10.1016/j.precamres.2004.08.004
Date Deposited: 10 Aug 2006
Last Modified: 18 Nov 2014 03:11
URI: http://eprints.utas.edu.au/id/eprint/343
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