Multi-mineral geochronology: insights into crustal behaviour during exhumation of an orogenic root
MetadataShow full item record
Under rare conditions, reworked cratons and their margins preserve the orogenic roots of ancient mountain-building events. However, based on the preservation of high-temperature (~ 800 °C), middle and lower crustal metamorphic assemblages, present day exposure of these terrains is not simply a result of protracted denudation, but also must reflect a multifaceted exhumational history. In situ analysis within thin section preserves the textural setting of target minerals that can be used as thermochronometers such as U-Pb of zircon, monazite, titanite and apatite, and Sm-Nd of apatite. In situ analyses of these chronometers has the potential to provide critical timing constraints on exhumation processes related to decompression, melting and cooling across large metamorphic terrains. The Repulse Bay block of the Rae craton preserves a large composite amphibolite–granulite area (50,000 km2) of Archean orthogneiss, migmatite, and slivers of Proterozoic metasediments that underwent high-grade metamorphism, partial melting, ductile flow and finally exhumation during the Paleoproterozoic Trans-Hudson Orogeny. The granulite domain preserves dry granitoid assemblages, whereas the amphibolite domain is dominated by hydrated migmatites and orthogneiss. Metasediments occur in both domains and preserve mineral assemblages that are consistent with having undergone tectonometamorphic conditions of ~ 9 kbar/800 °C during burial. U-Pb thermochronometers document identical cooling histories of the granulite and amphibolite domains through the U-Pb closure temperatures of titanite (~ 650 °C) and apatite (~ 450 °C). This suggests that melt-loss from the underlying granulite domain and melt-gain to the amphibolite domain prior to cooling through 650 °C are a controlling factor of the metamorphic assemblages across the composite granulite–amphibolite terrains such as the Repulse Bay block, rather than significant differences in burial history, cooling history, and/or reorganization of the crust.
Showing items related by title, author, creator and subject.
Rapid cooling and exhumation in the western part of the Mesoproterozoic Albany-Fraser Orogen, Western AustraliaScibiorski, E.; Tohver, E.; Jourdan, Fred (2014)The Albany-Fraser Orogen of southwestern Australia is an understudied orogenic belt, which is interpreted to record the Mesoproterozoic suturing of the Yilgarn Craton of Western Australia to the Mawson Craton of East ...
Neoproterozoic evolution and Cambrian reworking of ultrahigh temperature granulites in the Eastern Ghats Province, IndiaMitchell, R.; Johnson, Tim; Clark, Christopher; Gupta, S.; Brown, M.; Harley, S.; Taylor, Richard (2018)The time-scales and P–T conditions recorded by granulite facies metamorphic rocks permit inferences about the geodynamic regime in which they formed. Two compositionally heterogeneous cordierite–spinel-bearing granulites ...
Microstructurally controlled trace element (Zr, U–Pb) concentrations in metamorphic rutile: An example from the amphibolites of the Bergen ArcsMoore, Jo ; Beinlich, Andreas ; Porter, Jennifer K.; Talavera Rodriguez, Cristina ; Berndt, J.; Piazolo, S.; Austrheim, H.; Putnis, Andrew (2020)As a common constituent of metamorphic assemblages, rutile provides constraints on the timing and conditions of rock transformation at high resolution. However, very little is known about the links between trace element ...