Evidence for Hadean inheritance recorded in Mesoarchean granitoids from the Assean Lake Complex, Manitoba

Archean cratons represent the oldest preserved cores of continental crust, assembled through over two billion years of magmatism and crustal reworking. This protracted history obscures the nature of the progenitor materials that sourced the Neo- to Mesoarchean felsic rocks dominating most cratons. Although long-lived radiogenic isotopic systems provide insights into crustal evolution, they can be affected by post-magmatic processes, potentially leading to ambiguous interpretations, particularly when characterizing early crustal components absent in the geological record. The coupling of long-lived systems with short-lived isotopic tracers offers a more robust approach to resolving early crustal evolution. Here, we combine 147–146 Sm- 143–142 Nd isotopic systematics with whole-rock major and trace element geochemistry for ca. 3.2 Ga orthogneisses from the Assean Lake Complex (Manitoba, Canada) to constrain the age and origin of their crustal precursors. The 146 Sm- 142 Nd data indicate these Mesoarchean granitoids were derived from multiple crustal sources with distinct formation ages and composition. Sodic tonalite-trondhjemite-granodiorite (TTG) gneisses likely formed by partially melting a hydrated mafic crustal precursor (weighted mean µ 142 Nd ∼ -3.2) extracted from the mantle near the Hadean-Eoarchean transition. Conversely, coeval granitic gneisses were produced by reworking older TTG-like crust ultimately derived from a Hadean mafic reservoir (weighted mean µ 142 Nd ∼ -7.1). Together, these results provide direct evidence that the Assean Lake high-K granitoids inherited Hadean isotopic signatures through reworking of older crustal precursors ultimately derived from a Hadean mafic reservoir. They demonstrate that compositionally and temporally distinct crustal reservoirs, including ancient Hadean components, were mobilized and reworked contemporaneously during Mesoarchean magmatism, highlighting the dynamic, multi-source nature of early continental crust formation.