Mafic volcanic rocks on King Island, Tasmania: evidence for 579 Ma break-up in east Gondwana
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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Official URL: http://dx.doi.org/10.1016/j.precamres.2004.08.004
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.
|Keywords:||continental break-up; crustal contamination; large igneous province; picrite; rodinia; tasmania; southeastern australia|
|Deposited By:||utas eprints|
|Deposited On:||10 Aug 2006|
|Last Modified:||18 Jul 2008 19:42|
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