Charnockites and UHT metamorphism in the Bakhuis Granulite Belt, western Suriname : Evidence for two separate UHT events

摘要: Abstract The Bakhuis Granulite Belt in western Suriname is an ultrahigh-temperature (UHT) metamorphic terrain the centre of Paleoproterozoic (Transamazonian) Guiana Shield. Next to UHT granulites, belt contains a 30 by 30 km body orthopyroxene-bearing granitoids: Kabalebo charnockites. This setting offers excellent opportunity investigate source and origin charnockite magmatism common association charnockites with (ultra)high-temperature terrains. We present detailed geochemical dataset LA-ICPMS zircon U/Pb ages aim geochronological relationship between metamorphism Belt. have characteristic trace element signature elevated K 2 O, P O 5 , Zr, REE Ba coupled mobile depletion, which consequence high-temperature melting anhydrous but fertile granulitic crust. Field evidence suggests that intermediate granulites are new indicate (1993–1984 Ma) postdates (2.07–2.05 Ga) at least 60 Myr. argue it not possible maintain thermal anomaly >200 °C excess normal geothermal gradient for such prolonged period hence conclude has experienced two distinct periods temperatures >950 °C were reached lower presence comagmatic metadolerite enclaves establishes mafic occurred contemporaneously with, was likely heat for, 1.99–1.98 Ga. In contrast, 2.07–2.05 Ga event associated felsic or nearby Shield suturing juvenile North TTG-greenstone West African 10 Myr. postulate result mantle upwelling slab tear subducted formed as crustal scale shearing boudinage. Prior final stabilisation Amazonian–West 1.90 Ga, northward subduction 1.99–1.98 Ga caused emplacement voluminous hot, magma, resulting partial granulite suite form Charnockite roughly contemporaneous large shallow granites volcanic rocks SW Despite their similar age, inherited populations suggest derived from distinct, while include Archaean protolith.