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Facies architecture of the Early Devonian Ural Volcanics, New South Wales

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Bull, KF and McPhie, J (2006) Facies architecture of the Early Devonian Ural Volcanics, New South Wales. Australian Journal of Earth Sciences, 53 (6). pp. 919-945. ISSN 0812-0099

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Abstract

The Ural Volcanics are a early Devonian, submarine, felsic lava-sill complex, exposed in the western central Lachlan Orogen, New South Wales. The Ural Volcanics and underlying Upper Silurian, deepwater, basin-fill sedimentary rocks make up the Rast Group. The Ural Range study area, centrally located in the Cargelligo 1:100 000 map sheet area, was mapped at 1:10 000 scale. Seventeen principal volcanic facies were identified in the study area, dominated by felsic coherent facies (rhyolite and dacite) and associated monomictic breccia and siltstone-matrix monomictic breccia facies. Subordinate volcaniclastic facies include the pumice-rich breccia facies association, rhyolite - dacite -siltstone breccia facies and fiamme-siltstone breccia facies. The sedimentary facies association includes mixed-provenance and non-volcanic sandstone to conglomerate, black mudstone, micaceous quartz sandstone and foliated mudstone. The succession was derived from at least two intrabasinal volcanic centres. One, in the north, was largely effusive and intrusive, building a lava - sill complex. Another, in the south, was effusive, intrusive and explosive, generating lavas and moderate- volume (*3 km3) pyroclastic facies. The presence of turbidites, marine fossils, very thick massive to graded volcaniclastic units and black mudstone, and the lack of large-scale cross-beds and erosional scours, provide evidence for deposition in a submarine environment below storm wave-base. The Ural Volcanics have potential for seafloor or sub-seafloor replacement massive sulfide deposits, although no massive sulfide prospects or related altered zones have yet been defined. Sparse, disseminated sulfides occur in sericite-altered, steeply dipping shear zones.

Item Type: Article
Keywords: Devonian, facies architecture, felsic volcanic rocks, Lachlan Orogen, pyroclastics, submarine volcanism, Ural Volcanics.
Journal or Publication Title: Australian Journal of Earth Sciences
Page Range: pp. 919-945
ISSN: 0812-0099
Identification Number - DOI: 10.1080/08120090600686835
Date Deposited: 05 Jul 2007
Last Modified: 18 Nov 2014 03:18
URI: http://eprints.utas.edu.au/id/eprint/1308
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