The role of high-K I-type granites in Neoarchean craton stabilisation: insights from the Bundelkhand Craton, India

Two contrasting end-members of Archean crustal growth can be envisaged: one dominated by juvenile additions from a depleted mantle, and the other by extensive reworking and remelting of older, chemically evolved continental crust. Archean cratons preserve the earliest record of crust–mantle differentiation and extreme tectonics, yet the relative contributions of these two processes remain debated. We address this issue through an integrated field, petrographic, whole-rock geochemical, zircon U–Pb geochronological, and Lu–Hf isotopic study of Neoarchean high-K I-type granites from the Bundelkhand Craton, northern India. These metaluminous to weakly peraluminous granites (SiO₂ 64–76 wt.%) intrude Palaeo- to Mesoarchean tonalite–trondhjemite–granodiorite (TTG) gneisses and display LILE-enriched, Nb–Ti–Sr-depleted, arc-like trace-element signatures, consistent with generation in a convergent-margin or arc-related geodynamic setting. New zircon U–Pb ages of 2559 ± 16 Ma, 2530 ± 12 Ma, and 2520 ± 26 Ma define a ~30 Myr-long episode of Neoarchean felsic magmatism, marking a protracted period of late Archean thermal and magmatic activity in the Bundelkhand Craton. Zircon εHf(t) values ranging from –9.3 to –1.9, together with two-stage Hf model ages of ca. 3.0–3.4 Ga, indicate that these granites were generated predominantly by partial melting of Meso- to Palaeoarchean TTG and mafic lower crust, with only limited input from juvenile, depleted-mantle–derived magmas. Zircon solubility in silicate melts and Ti in Zircon thermometry yield crystallisation temperatures of ~720–800 °C, while pressure estimates indicate emplacement at shallow to mid-crustal levels (~3–19 km), reflecting thickening of an already stabilised cratonic root.

The Lu–Hf signatures of the Bundelkhand granites provide an important basis for comparison with other Neoarchean cratons. Coeval granitoid suites in the North China Craton typically show more juvenile, near-chondritic to positive εHf(t) values, reflecting substantial additions of depleted-mantle–derived magmas during Neoarchean crustal growth. In contrast, the strongly negative εHf(t) values obtained for the Bundelkhand granites closely resemble those reported from Neoarchean granitoids in the Zimbabwe Craton, where crustal reworking and remelting of Neoarchean–Mesoarchean crust dominate over juvenile additions. The Bundelkhand high-K I-type granites, therefore, represent a crustal reworking-dominated end-member of late Archean continental growth. Placed within a Kenorland framework, our results emphasise that parts of the Indian shield evolved through prolonged reworking of older continental lithosphere rather than large-scale juvenile accretion, and they provide first-order constraints on the geodynamic regimes that governed late Archean continental assembly.

Keywords
Archean cratons; Bundelkhand Craton; Neoarchean granite magmatism; zircon U–Pb geochronology; Lu–Hf isotopes; crustal reworking; North China Craton; Zimbabwe Craton; Kenorland.