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Surface and subsurface facies architecture of a small hydroexplosive, rhyolitic centre in the Mesoproterozoic Gawler Range Volcanics, South Australia

Citation

Roache, MW and Allen, SR and McPhie, J, Surface and subsurface facies architecture of a small hydroexplosive, rhyolitic centre in the Mesoproterozoic Gawler Range Volcanics, South Australia, Journal of Volcanology and Geothermal Research, 104, (1-4) pp. 237-259. ISSN 0377-0273 (2000) [Refereed Article]

DOI: doi:10.1016/S0377-0273(00)00208-0

Abstract

At Menninnie Dam, South Australia, a drilling program has revealed a complete section through the subsurface feeder system and erupted products of a small, hydroexplosive, rhyolitic centre within the Mesoproterozoic Gawler Range Volcanics. Porphyritic rhyolite intruded near-vertical faults in the Palaeoproterozoic basement and at less than a few hundred metres depth, interacted with fault-hosted (hot?) groundwater. Hydrofracturing of the wall rock occurred in advance of and at the margins of the ryolitic intrusions. The rhyolitic intrusions have peperitic margins and grade into discordant lithic-rich PB facies. The advancing fragmentation front intersected the palaeosurface, triggering phreatic eruptions that deposited a poorly sorted, lithic-rich explosion breccia. Rhyolite then rose to the surface through the intrusive breccias and shallow-seated magma-water interaction occurred in the conduit within<50 m of the surface. As the magma discharge rate increased. "dry" explosive activity prevailed. A fall deposit, the top of which is welded, was deposited close to the vent, and in more distal locations(>800 m from the inferred source), the products include muddy sandstone and pumice breccia. At the end of the eruption, rhyolitic lava was extruded in the form of a small dome. The presence of contemporaneous Pb-Zn-Ag mineralisation in the wall rocks suggests that an active hydrothermal system may have been involved in the formation of the Menninnie Dam hydroexplosive volcanic centre. © 2000 Elsevier Science B.V. All rights reserved.

Item Details

Item Type:Refereed Article
Research Division:Earth Sciences
Research Group:Geology
Research Field:Volcanology
Objective Division:Expanding Knowledge
Objective Group:Expanding Knowledge
Objective Field:Expanding Knowledge in the Earth Sciences
Author:Allen, SR (Dr Sharon Allen)
Author:McPhie, J (Professor Jocelyn McPhie)
ID Code:23258
Year Published:2000
Web of Science® Times Cited:7
Deposited By:Centre for Ore Deposit Research - CODES CoE
Deposited On:2001-08-01
Last Modified:2011-11-18
Downloads:0

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