Geochemistry of the Mount Windsor Volcanics; implications for the tectonic setting of Cambro-Ordovician volcanic-hosted massive sulfide mineralization in northeastern Australia

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doi: 10.2113/gsecongeo.90.5.1080
Authors:Stolz, A. J.
Author Affiliations:Primary:
University of Tasmania, Centre for Ore Deposit and Exploration Studies, Hobart, Tasmania, Australia
Volume Title:Economic Geology and the Bulletin of the Society of Economic Geologists
Source:Economic Geology and the Bulletin of the Society of Economic Geologists, 90(5), p.1080-1097. Publisher: Economic Geology Publishing Company, Lancaster, PA, United States. ISSN: 0361-0128
Publication Date:1995
Note:In English. 63 refs.; illus., incl. sects., 5 tables, sketch maps
Summary:The Mount Windsor subprovince is an important relic of Upper Cambrian to Lower Ordovician sedimentation and volcanism in the northern part of the Tasman orogenic zone. Volcanic-hosted massive sulfide mineralization occurs at several stratigraphic horizons within the volcano-sedimentary package and one major mine is operational within the belt. Major and trace element data and Nd isotope ratios are presented for the least altered coherent units from the three major volcanic-bearing formations in the Mount Windsor subprovince. The data are used to discriminate four major phases of volcanism and related intrusive activity derived from three isotopically discrete sources and to assess the geodynamic setting in which the volcanism occurred. The earliest phase of mafic volcanism has minor and trace element characteristics suggesting an alkaline intraplate or rift association and it was probably produced by partial melting of attenuated subcontinental lithospheric mantle. The overlying Mount Windsor Formation silicic volcanics have Nd isotope characteristics (εNd(480 Ma) = -4.7 to -12.8) that suggest they were produced by partial melting of underlying Precambrian crustal rocks. Mafic volcanics of the overlying Trooper Creek Formation include a low TiO2 suite and a high TiO2 suite with a range of distinguishing chemical characteristics but similar Nd isotope ratios (εNd(480 Ma) = 3.8-2.3), which indicate derivation from relatively depleted asthenospheric mantle variably modified by subduction processes. The high TiO2 suite is also represented by abundant intrusions within the underlying volcanic package. The more silicic volcanics in the Trooper Creek Formation appear to be cogenetic with their mafic associates but have varying Nd isotope ratios, which suggest progressive crustal interaction with increasing SiO2 content. Comparisons with modern volcanic compositions and ore depositional environments suggest that the volcanic and sedimentary units within the Mount Windsor subprovince were deposited in a back-arc basin developed by extension of continental lithosphere along the eastern Australian margin in the Late Cambrian and Early Ordovician. Mineralization and volcanic deposits of similar age farther north in the Tasman orogenic zone suggest that this basin may have had a north-south orientation, although there is no clear evidence remaining of the original arc front deposits.
Subjects:Basalts; Cambrian; Copper ores; Dikes; Geochemistry; Geodynamics; Gold ores; Host rocks; Igneous rocks; Intrusions; Isotope ratios; Isotopes; Lead ores; Lithosphere; Major elements; Mantle; Massive deposits; Massive sulfide deposits; Metal ores; Metals; Mid-ocean ridge basalts; Mineral deposits, genesis; Mineralization; Nd-144/Nd-143; Neodymium; Ordovician; Paleozoic; Partial melting; Rare earths; Sedimentary rocks; Sedimentation; Stable isotopes; Tectonics; Trace elements; Volcanic rocks; Volcanism; Zinc ores; Australasia; Australia; Queensland Australia; Tasman orogenic zone; Mount Windsor Subprovince; Mount Windsor Volcanics; Northeastern Australia; Puddler Creek Formation; Trooper Creek Formation
Abstract Numbers:96M/4248
Record ID:1996008585
Copyright Information:GeoRef, Copyright 2019 American Geosciences Institute.
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