Temporal constraints on Palaeoproterozoic eclogite formation and exhumation (Usagaran Orogen, Tanzania)
MetadataShow full item record
In-situ rock suites that preserve assemblages consistent with metamorphism to eclogite-facies conditions are absent from the Archaean. Their Palaeoproterozoic appearance is one of the markers of the onset of tectonic processes similar to those seen in the Phanerozoic Earth. We report new U Pb Secondary Ion Mass Spectrometry (SIMS) zircon data from the oldest known eclogites (the 2.0 Ga Usagaran eclogites, Tanzania) that constrain the timing of high-grade metamorphism, deformation and exhumation of these eclogites and constrain the speed of these processes at this critical period in Earth history.Direct dating of metamorphic zircon from mafic eclogites, and isostructurally recrystallised zircon rims from pelites and felsic gneisses indicates that high-grade metamorphism occurred at 1999.11.1 Ma. The rocks were quickly cooled and exhumed at rates of 25 C/Ma and 0.06 0.22 GPa/Ma, respectively, at least in part, by amphibolite-facies sinistral transpression constrained by a 19912 Ma pegmatite dyke that crosscuts foliation. Detrital zircons in metasedimentary gneiss protoliths were dominantly derived from two sources: (1) the Tanzanian craton, and (2) a 2400 2640 Ma source region that is compatible with a belt of reworked Archaean and Palaeoproterozoic rocks that lie in the East African Orogen.
Copyright 2006 Elsevier B.V. All rights reserved
Showing items related by title, author, creator and subject.
Geochronology of Paleoproterozoic Augen Gneisses in the Western Gneiss Region, Norway: Evidence for Sveconorwegian Zircon Neocrystallization and Caledonian Zircon DeformationRøhr, T.; Bingen, B.; Robinson, P.; Reddy, Steven (2013)The Western Gneiss Region, Western Norway, consists of Palaeoproterozoic crust of Baltica ancestry (Baltican Basement), partly subducted to high- and ultrahigh-pressure (HP-UHP) conditions during the Scandian Orogeny ...
Fluid generation and evolution during exhumation of deeply subducted UHP continental crust: Petrogenesis of composite granite-quartz veins in the Sulu belt, ChinaWang, S.; Wang, L.; Brown, M.; Piccoli, P.; Johnson, Tim; Feng, P.; Deng, H.; Kitajima, K.; Huang, Y. (2017)Composite granite-quartz veins occur in retrogressed ultrahigh pressure (UHP) eclogite enclosed in gneiss at General's Hill in the central Sulu belt, eastern China. The granite in the veins has a high-pressure (HP) mineral ...
Complex high strain deformation in the Usagaran Orogen, Tanzania: structural setting of Palaeoproterozoic eclogitesReddy, Steven; Collins, Alan; Mruma, A. (2003)The Palaeoproterozoic Usagaran orogenic belt of Tanzania contains the Earth's oldest reported examples of subduction-related eclogite facies rocks. Detailed field mapping of gneisses exposed in the high-grade, eclogite-bearing ...