Archean Crustal Evolution in the Bundelkhand Craton, India: Constraints from Whole Rock Sr-Nd and Zircon U-Pb/Hf Isotopes

The formation and reworking of the continental crust is of great importance for understanding the early evolution of the Earth. Combining U-Pb/Hf isotopes in zircons with whole rock geochemical and Sr-Nd isotopic data can provide new insights on petrogenetic mechanisms, timing of magmatic events, crust-mantle interactions and magma sources for crustal material. To understand the evolution and reworking of the continental crust we measured a dataset of in situ zircon U-Pb, Hf and combined it with whole-rock Sr and Nd analyses for Archean TTGs and geochemically variable high-K granitoids from the Bundelkhand Craton, India. U-Pb zircon ages reveal that the TTGs were emplaced at 3.42 Ga, 3.33 Ga and 2.72 Ga, while the high-K granites, including sanukitoids, were emplaced between 2.57 Ga and 2.54 Ga. The high-K granitoids with higher 87Sr/86Sr (0.717335-1.243294), lower ɛHf (from -8.9 to +0.4) have ɛNd in the range of -29.58 to -47.46 as compared with the TTGs which have lower 87Sr/86Sr (0.721982-0.877271) and higher ɛHf (from -1.6 to +5.9) while their ɛNd range from -26.86 to -36.86 respectively. The Hf depleted mantle model ages calculated for high-K granitoids are 3.19-2.86 Ga and for TTGs 3.71-3.48 Ga. The U-Pb ages and chondritic to superchondritic ɛHf values of the TTGs provide evidence for a long-term episodic growth of juvenile crust from depleted mantle reservoirs between 3.4 and 2.7 Ga. The strongly negative ɛHf values of the high-K granitoids, together with geochemical features (variable compatible and incompatible elements) indicate that they were a result of multi-stage reworking of the Paleo- to Neoarchean crust and mixing with magmas extracted from an enriched mantle source during a relatively short-lived tectonic event at the end of the Archean that led to the stabilization of the craton.