Geochemistry and petrogenesis of magnesian high-K granitoids from Bundelkhand Craton, Central India: New insights into crustal evolution

Abstract

Background

The Bundelkhand Craton is significant for preserving the multiphase granitoids magmatism from Paleoarchean to Neoarchean periods. It consists of a variety of granite rocks, including TTGs, sanukitoids, and high-K granitoids. This study presents geochemical characteristics of high-silica (68.97 wt.%–73.99 wt.%), low-silica (58.73 wt.%–69.94 wt.%), and high K₂O (2.77 wt.%–6.16 wt.%) contents of granitoids.

Objective

The data on Bundelkhand Craton's granitic magmatism and geodynamics is not sufficiently robust. Geochemical data from this study will be used to further understand the origin, source, and petrogenesis of granitoid rocks and their implications for the evolution of geodynamics.

Methodology

Twenty-one samples were collected and analyzed for major, trace, and REE elements. Major elements were measured using X-ray fluorescence spectrometry (XRF), and trace and REE elements were analyzed by ICP-MS. Standard procedures from the Geological Survey of India were followed.

Results

The geochemical analysis presents high-silica (68.97-73.99 wt. %), low-silica (58.73-69.94 wt. %), and high K2O (2.77-6.16 wt. %) contents in granitoids, classified as granite-granodiorite. The rocks are calcic to calcalkalic, magnesian, and range from peraluminous to metaluminous composition. REE patterns showed strong LREE enrichment relative to HREEs, with prominent negative Eu anomalies corresponding to earlier plagioclase fractionation. Multi-element patterns revealed negative anomalies in Nb, Sr, P, and Ti and positive anomalies in Pb.

Conclusion

The geochemical signatures attributed to the post-collisional magma generation and continental crustal contamination. The studied rocks show A-type and A2-type lineage, suggesting they originated from the melting of continental crust during transitional/post-collisional tectonic activity. The formation of hybrid granitoids in the Bundelkhand Craton is connected to the fractionation of hybrid magmas in shallow-seated magma chambers during these tectonic processes.