Archean crustal evolution of the Aravalli Banded Gneissic Complex, NW India: Constraints from zircon U-Pb ages, Lu-Hf isotope systematics, and whole-rock geochemistry of granitoids

Abstract

Abstract The Aravalli Banded Gneissic Complex forms a block of Archean gneisses and granitoids in the southern domain of the Aravalli orogen in NW India. Results of U-Pb-Hf isotope analyses on zircon grains combined with whole-rock geochemical data reveal that the gneissic complex is made up of TTGs, which intruded during the Paleoarchean (3310\u202fMa) and Neoarchean (2563–2548\u202fMa), and granite-granodiorite-quartz diorite emplaced between 2545 and 2485\u202fMa. Zircon xenocrysts additionally point to Meso- and Neoarchean magmatic episodes at 3100–3000, 2880–2800, 2690 and 2660–2630\u202fMa. Ages from zircon rims in conjunction with previously published Sm-Nd isotope data suggest metamorphic events at ca. 2450 and 520\u202fMa. Medium-HREE characteristics and near chondritic eHf3.31 Ga of −0.4 suggest formation of the Paleoarchean TTGs by partial melting of a deep-seated mafic crust, derived from CHUR-like mantle immediately prior to the TTG formation. In contrast, the high-HREE characteristics and subchondritic eHf2.56-2.55 Ga from −3 to −8 of the Neoarchean TTGs suggest partial melting at relatively shallow depth of a younger oceanic crust, which was derived from a depleted mantle source at