Radioelemental, petrological and geochemical characterization of the Bundelkhand craton, central India: implication in the Archaean geodynamic evolution

Abstract

with radioelemental ratios suggest that radioelemental variations in these lithounits are mainly related to abundances of the radioactive minerals that have formed by the fractionation of LILE from different magma sources. Based on present data, the craton can be divided into three distinct zones that can be correlated with its evolution in time and space. The central part, where gneisses are associated with metavolcanics of greenstone belt, is characterized by lowest radioelements and is the oldest component. The southern part, dominated by pink granitoid, is characterized by highest radioelements and is the youngest part. The northern part, dominated by grey and biotite granitoid, is characterized by moderate radioelements.

Reddening of ~2.5 Ga granitoid by high‐temperature fluid linked to mafic dyke swarm in the Bundelkhand Craton, north central India

“…The implication is that the red colouration of the granitoids is not attributable to modal abundances of primary magmatic K‐feldspar contents in these rocks. Therefore, we do not find any direct link between red colouration to flesh red coloured K‐feldspar abundance in the granitoid rocks, contrary to what earlier workers including Ray et al () have described.…”

“…The prevalent notion for red colouration in granitoids would normally be considered because of modal dominance of “red‐coloured” alkali feldspars over other minerals including albitic plagioclase. In fact, this perhaps guided earlier workers including Ray et al () to identify K‐feldspar‐rich granitoids in the field as pink granitoids.…”

Heat flow, heat production, and crustal temperatures in the Archaean Bundelkhand craton, north‐central India: Implications for thermal regime beneath the Indian shield

“…Petrographic studies indicate that apatite, zircon, sphene, magnetite, rutile, epidote, and allanite are the common accessory minerals in these rocks and show that similar radioactive minerals are present in the various types of granites and gneisses. The variations in Th and U concentrations within the granites as well as variations between the granites and gneisses could be related qualitatively with the proportion of individual radioactive minerals present in the respective rock types [ Ray et al ., ].…”

“…On average, Th accounts for ~50%, whereas U accounts for ~40% to the total heat production for all the rock types. The large variability in Th and U concentrations in granites and gneisses could be due to their different origin or distinctive crustal and mantle‐derived contributions involved in geological processes as it is revealed from geochemical study that granites and TTG gneisses of the Bundelkhand craton are metaluminous to peraluminous in character [ Ray et al ., ]. Also, there are opinions that in the Bundelkhand craton, a number of plutons have come together to give rise to major batholiths [ Mondal and Zainuddin , ], which may have contributed to the variability in Th and U concentrations.…”

“…Because of lack of data for rock formations in a particular region, modeling studies often resort to using radiogenic heat production for similar rock type determined from measurements in other tectonic provinces. However, the variability of radioelement concentrations, even within the same rock type in a geologic province, is quite well recognized [ Roy , , and references therein; Ray et al ., , ]. The Indian shield, with abundant exposures of different crustal rocks, provides ample opportunities to sample and measure the radioelement concentrations.…”