Over one billion years of Archean crust evolution revealed by zircon U-Pb and Hf isotopes from the Saglek-Hebron complex

The Saglek-Hebron Complex (SHC) located in Northern Labrador, Canada, includes some of the oldest crustal rocks on Earth. This granite-greenstone terrain is dominated by trondhjemite, Mg-rich tonalite, granite, with subordinate granodiorite, and recorded over one billion years early magmatic history between ∼3900 Ma ∼2700 Ma. New in-situ U-Pb analyses zircons from eighteen rock samples, suggest that six distinct events formed felsic crust SHC, during Archean Eon. Age deconvolution analysis constrains these episodes at ca. 3857 Ma, 3744 3575 3330 3224 2750 respectively defined as Iqaluk, Uivak I, II, Iluilik, Lister late granite events. Iluilik represents a newly event, event previously recognized ∼3200 Uranium-Pb geochronology, combined Hf isotopic data geochemistry host rocks, reveal complex protracted SHC marked reworking mafic years. Zircons Iqaluk I samples yield slightly suprachondritic initial εHf values (up to ∼+4), consistent involvement long-term depleted source Eoarchean. granodiorite exhibits low value −6, clearly diverging near-chondritic composition tonalites. Considering precursor (with 176Lu/177Hf ratio ∼0.02) for trondhjemite-tonalite-granodiorite (TTG) compositions Eoarchean Paleoarchean would be Hadean crust. zircon vs. time trend corresponds ∼0.01, suggesting granitic was mainly produced TTG. Similarly Itsaq Gneiss SW Greenland, granitoids appear record shift more juvenile end Paleoarchean. However, contrary what observed almost no input material has been Neoarchean