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Title: Mineral chemistry, petrogenesis, and tectonic setting of the Wateranga layered intrusion, Southeast Queensland, Australia
Contributor(s): Talusani, RVR (author); Sivell, Warwick John (author); Ashley, Paul (author)
Publication Date: 2005
DOI: 10.1139/e05-077
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Abstract: The Wateranga layered mafic intrusion (28 km² in area, > 500 m thick) is a tholeiitic, undeformed, unmetamorphosed, Permo-Triassic layered gabbroic pluton intruded into the late Carboniferous Goodnight beds of the Goodnight Block in southeast Queensland. The intrusion mainly consists of gabbro and norite, associated with subordinate amounts of troctolite, anorthosite, and orthopyroxenite, and rare picrite. Olivine gabbro is the dominant rock type of the intrusion. Fractionation followed a tholeiitic trend with iron enrichment in the liquid. Petrographic, mineral chemical, and whole-rock geochemical data have been used to divide the intrusion into Lower, Middle, and Upper zones, which are interpreted as reflecting magma chamber replenishment. The observed changes in the crystallization order between the zones reveal that a single parental magma is inadequate to explain the data. The common differentiation indices, such as An content of plagioclase, Mg#s of olivine, clinopyroxene, orthopyroxene and whole-rocks, and the whole-rock concentrations of various incompatible trace elements (Zr, Y, Nb, La Ba, Rb, Sr, and Nd), all vary widely with stratigraphic depth and display abrupt shifts at the zone boundaries, indicating open system addition of new mafic magma. Temperatures estimated from two-pyroxene geothermometer vary from 1057 to 927°C. During the course of crystallization, pressure probably was > 2 and < 4 kbar (1 kbar = 100 MPa). The variation trend of anorthite content of plagioclase versus the forsterite content of olivine precludes an arc-related magma source. The composition and geological setting of the intrusion are consistent with emplacement in a post-subduction extensional tectonic environment.
Publication Type: Journal Article
Source of Publication: Canadian Journal of Earth Sciences, 42(11), p. 1967-1985
Publisher: NRC Research Press
Place of Publication: Ottawa, Canada
ISSN: 0008-4077
Field of Research (FOR): 040304 Igneous and Metamorphic Petrology
Peer Reviewed: Yes
HERDC Category Description: C1 Refereed Article in a Scholarly Journal
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School of Environmental and Rural Science

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