Please use this identifier to cite or link to this item: https://hdl.handle.net/2440/133473
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Type: Journal article
Title: Pressure-temperature-time constraints on gneiss dome formation in an intracontinental orogen
Author: Varga, J.
Raimondo, T.
Morrissey, L.
Kelsey, D.E.
Hand, M.
Citation: Journal of Metamorphic Geology, 2022; 40(3):457-488
Publisher: Wiley
Issue Date: 2022
ISSN: 0263-4929
1525-1314
Statement of
Responsibility: 
Jan Varga, Tom Raimondo, Laura Morrissey, David E. Kelsey, Martin Hand
Abstract: The Entia Gneiss Complex represents the mid-crustal core of the intracontinental Alice Springs Orogen. Located in the Harts Range, central Australia, it is characterized by the development of a domal structure including two sub-domes separated by a steeply dipping median high-strain zone. Dominantly, orthogneiss basement crops out through a structurally overlying cover sequence represented by the Harts Range Group and records evidence of hydration, recrystallization, and partial melting of precursor Paleoproterozoic granulite facies assemblages at amphibolite facies conditions. The structurally lowest parts of the Harts Range Group were metamorphosed to peak conditions of 10.5 kbar and 880C during rift-related magmatism at 480–460 Ma, immediately prior to the onset of the Alice Springs Orogeny at 450–300 Ma. By contrast, the underlying Entia Gneiss Complex records widespread metamorphism and wet melting at upper amphibolite facies conditions. Phase equilibrium modelling and in situ LA–ICP–MS geochronology of rare, low-variance kyanite–garnet-bearing metapelites indicate that maximum P–T conditions of 9 kbar and 680C were reached between c. 360–330 Ma, demonstrating a distinctive metamorphic and temporal evolution relative to the overlying Harts Range Group that can be linked to rheological stratification. Based on the integration of our results with existing monazite, zircon, and titanite geochronology, we interpret doming of the Entia Gneiss Complex to have involved compressive ascent of rheologically weakened crust below a region of extending upper crust near the termination of the Alice Springs Orogeny. In this way, the Harts Range Group represents a cooled, locally extending thrust sheet over ductile basement quasi-concurrent with doming. Texturally-late sillimanite combined with increasing Y content in monazite indicates high-temperature, kyanite-grade metamorphism was closely followed by decompression (3–4 kbar drop from peak conditions) and rapid cooling below 600C during emplacement of the Entia Gneiss Complex at shallower crustal levels. The findings of this study highlight the feedback between hydration, retrogression, rheological weakening, and strain accommodation, thus allowing better evaluation of the thermomechanical history of gneiss dome formation within a narrow (<80 km wide) preconditioned intracontinental corridor.
Keywords: Entia Gneiss Complex; gneiss dome; intracontinental; phase equilibrium modelling; U–Pb monazite geochronology
Description: First published: 12 September 2021
Rights: © 2021 John Wiley & Sons Ltd
DOI: 10.1111/jmg.12635
Grant ID: http://purl.org/au-research/grants/arc/DP160103449
Published version: http://dx.doi.org/10.1111/jmg.12635
Appears in Collections:Geology & Geophysics publications

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