Building Mesoarchaean crust upon Eoarchaean roots: the Akia Terrane, West Greenland

摘要: Constraining the source, genesis, and evolution of Archaean felsic crust is key to understanding growth stabilization cratons. The Akia Terrane, part North Atlantic Craton, West Greenland, comprised Meso-to-Neoarchaean orthogneiss, with associated supracrustal rocks. We report zircon U–Pb Lu–Hf isotope data, whole-rock geochemistry, from samples gneiss supracrustals northern including Finnefjeld Orthogneiss Complex, which has recently been interpreted as an impact structure. Isotope data record two major episodes continental production at ca. 3.2 3.0 Ga. Minor 2.7 2.5 Ga magmatic events have more evolved eHf, reworking existing perhaps linked terrane assembly. Felsic rocks Complex were derived same source time surrounding tonalites, but shallower melting, requiring any bolide-driven melting event occurred almost simultaneously alongside crust. A simpler alternative tonalite representing coeval genesis over a substantial lithospheric depth. Hafnium Mesoarchaean crust-forming contribution older mafic Eoarchaean Invoking involvement root in younger puts important constraints on geodynamic models formation discrete terranes that ultimately assembled form Earth’s