Pourteau, A, Doucet, LS, Blereau, ER orcid.org/0000-0001-8850-397X et al. (5 more authors) (2020) TTG generation by fluid-fluxed crustal melting: Direct evidence from the Proterozoic Georgetown Inlier, NE Australia. Earth and Planetary Science Letters, 550. 116548. p. 116548. ISSN 0012-821X
Abstract
Across the Archaean to Proterozoic transition, the composition of newly-formed felsic continental crust changed from tonalite–trondhjemite–granodiorite (TTG) to calc-alkaline granitoid, possibly coinciding with the emergence of plate tectonics. Nevertheless, TTG suites were sporadically produced in Proterozoic and Phanerozoic orogenic belts, and such occurrences may provide petrological and tectonic insights into the formation of ancient continents. Here we demonstrate that the ca 1560 Ma Forest Home TTG plutonic suite in the Georgetown Inlier, NE Australia, was derived from partial melting of spatially-associated mafic rocks in a post-collisional setting. The studied TTG rocks have a ‘high-pressure’ geochemical signature, with elevated Sr, low heavy rare earth element and low high field strength element contents. Established petrogenetic models suggest they were derived by partial melting either of hydrated basaltic crust at >70 km depth or enriched lithospheric mantle, or by fractionation of lower-pressure mafic magmas. Using phase equilibrium calculations and trace-element modelling, we show that the geochemical signature of the Georgetown TTG likely resulted from fluid-fluxed crustal melting at relatively shallow depths (25–35 km), consistent with field observations and the inferred metamorphic evolution of the inlier. Our results suggest that the chemical variability of TTGs can reflect the variable availability of fluids rather than depth of melting, which has implications for tectonic processes responsible for the formation of early continental crust.
Metadata
Item Type: | Article |
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Authors/Creators: |
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Keywords: | Proterozoic, TTG, amphibolite, phase equilibrium and trace-element, modelling, fluid-fluxed melting, continental crust formation |
Dates: |
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Institution: | The University of Leeds |
Academic Units: | The University of Leeds > Faculty of Environment (Leeds) > School of Earth and Environment (Leeds) > Inst of Geophysics and Tectonics (IGT) (Leeds) |
Depositing User: | Symplectic Publications |
Date Deposited: | 26 May 2023 15:19 |
Last Modified: | 26 May 2023 15:19 |
Status: | Published |
Publisher: | Elsevier |
Identification Number: | 10.1016/j.epsl.2020.116548 |
Open Archives Initiative ID (OAI ID): | oai:eprints.whiterose.ac.uk:198418 |