Aravalli A-type granites (ca. 1.72 Ga), NW India: Petrogenesis, geodynamic evolution, and global implications for late Paleoproterozoic crustal reworking

• Ca. 1720 Ma A-type granites formed by partial melting of Neoarchean dioritic crust. • Crustal melting triggered by magmatic underplating in post-collisional setting. • Global late Paleoproterozoic A-type granites formed by reworking of older crust. The geochemical and isotopic data for ca. 1.72 Ga A-type granites in the central Aravalli orogen, NW India, remain limited, hindering a detailed evaluation of their petrogenesis and tectonic setting. New results of combined zircon U-Pb-Hf isotope analyses and whole-rock geochemical data reveal that the A-type granites are characterised by high liquidus temperatures (≥850 °C), enrichment in rare earth elements and incompatible elements, and oxidised in nature. They were generated through partial melting of a silica-poor dioritic source within a post-collisional extensional setting. This A-type magmatism is synchronous with the emplacement of charnockites and granulite-facies metamorphism in the region. The coeval formation of A-type and charnockite magmas is attributed to partial melting of evolved Neoarchean crust (εHf t = -12.5 to −5.2 and T DM2 = 3.02 to 2.68 Ga) at moderate depth (20–25 km), triggered by upwelling of asthenospheric mantle following a slab break-off at ca. 1730 Ma. This process induced lithospheric extension and granulite-facies metamorphism in the lower crust. A global compilation of zircon Hf isotope and whole-rock Nd isotope data for late Paleoproterozoic A-type granites suggests that these rocks primarily formed by large-scale reworking of existing crustal sources, with only limited melt contributions from depleted mantle sources, thereby having a negligible impact on crustal growth over time. On the contrary, the Phanerozoic A-type granites largely represent addition of new crust.