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Evolution and emplacement of high fluorine rhyolites in the Mesoproterozoic Gawler silicic large igneous province, South Australia

journal contribution
posted on 2023-05-17, 14:50 authored by Agangi, A, Vadim Kamenetsky, Jocelyn McPhieJocelyn McPhie
The Gawler Range Volcanics (GRV) and the Hiltaba Suite (HS) of South Australia form a silicic-dominated large igneous province (the Gawler SLIP) emplaced in an intracontinental setting during the Mesoproterozoic. Emplacement of the GRV lasted for a short period of time (∼2Ma), and can be separated into two main phases. The first phase (lower GRV) is composed of thick (≤3km) sequences erupted from distinct centres, and includes small to moderate volume (up to >150km 3) felsic lavas, ignimbrites, and minor mafic and intermediate lavas. The upper GRV include extensive felsic lavas that are up to >1000 of km 3 in volume and >200km across. Using well preserved, quartz-hosted melt inclusions, we investigated the composition of the lower GRV, including major, trace, and volatile elements. The results indicate high concentrations of K 2O (≤7-8wt.%), rare earth and high field strength elements, and low concentrations of Ca, Mg, Ni, Cr, Sr and Ba in comparison with felsic continental crust. Overall, melt inclusion compositions match whole-rock geochemical characteristics. We demonstrate that the GRV magma was F-rich (≤1.3wt.%), and had high temperature for a silicic magma. High F concentrations and high temperature would have resulted in lower than usual polymerisation of the melt and relatively low viscosity. These characteristics help explain how very voluminous felsic magma was erupted effusively and emplaced as lavas. Other intracontinental SLIP contain extensive felsic lavas and ignimbrites which appear to share similar geochemical characteristics. We also show that selective alteration caused depletion of whole-rock compositions in some trace elements, namely Pb, U, and Sn. © 2012 Elsevier B.V.

Funding

Australian Research Council

AMIRA International Ltd

ARC C of E Industry Partner $ to be allocated

Anglo American Exploration Philippines Inc

AngloGold Ashanti Australia Limited

Australian National University

BHP Billiton Ltd

Barrick (Australia Pacific) PTY Limited

CSIRO Earth Science & Resource Engineering

Mineral Resources Tasmania

Minerals Council of Australia

Newcrest Mining Limited

Newmont Australia Ltd

Oz Minerals Australia Limited

Rio Tinto Exploration

St Barbara Limited

Teck Cominco Limited

University of Melbourne

University of Queensland

Zinifex Australia Ltd

History

Publication title

Precambrian Research

Volume

208-211

Pagination

124-144

ISSN

0301-9268

Department/School

School of Natural Sciences

Publisher

Elsevier BV

Place of publication

Po Box 211, Amsterdam, Netherlands, 1000 Ae

Rights statement

Copyright 2012 Elsevier B.V.

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Expanding knowledge in the earth sciences

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