U–Pb systematics of the western Dharwar Craton - Glimpses of a billion year history of crustal evolution and relations to ancient supercratons

F Corfu,V.S Hegde

doi:10.1016/j.jsames.2020.102659

Abstract

The Dharwar Craton developed progressively over a billion years, through two main stages of crustal growth separated by a few-hundred million year long period of relative quiescence. The first stage between 3.4 and 3.0 Ga developed a proto-craton, which was considerably amplified during the second main stage between 2.7 and 2.4 Ga, through extensive magmatism, tectonism, and crustal consolidation. This paper reports U–Pb dating results obtained in four specific areas of the craton, with the data encompassing key moments in this long development. Rocks formed during the proto-craton stage include a 3089 Ma augen gneiss and a 2973 Ma evolved granite, the latter of which marks the final cratonization event of the proto-craton. The beginning of the second main stage is recorded in this study by 2650 Ma tonalite and trondhjemite, a 2623 Ma granite dyke cutting augen gneiss, and 2614, 2602 and 2588 Ma volcanic rocks. Titanite responded differently to the long evolution, as a function of location and type of overprint. It preserved an original 2973 Ma magmatic age in the west, but was reset and/or crystallized during secondary events in central domains of the craton, yielding ages between 2590 and 2360 Ma. A diorite stock intruded at 2207 Ma in the consolidated crust. It is correlated with the Anantapur-Kunigal mafic dyke swarm, one of a series of such events in the Dharwar Craton between 2.35 and 1.79 Ma. In terms of its overall evolution the Dharwar Craton has an affinity with the Slave clan, which includes the Wyoming and Zimbabwe cratons. It also matches many features in the evolution of the São Francisco Craton, a probable other member of Sclavia. This is in contrast to the Amazonian Craton, which has more affinity with the Superior clan.

Highlights

Archean cratons developed progressively by the interplay of two main processes: the gradual accumulation of mafic-ultramafic lithologies extracted from the mantle, and their subsequent reworking and refining into more evolved continental crust
The presence of more than one titanite generation is suggested by some of the published data, for example at Gadag (Sarma et al, 2011). Given this susceptibility of titanite for resetting or new growth/overgrowth, the preservation of the original titanite in the KMK pluton is remarkable, and can only be understood as indicating the lack of substantial post-magmatic activity. This refers to the 2.6–2.4 Ga events of magmatism and metamorphism that affected much of the craton, and the Mesoproterozoic activity that was postulated along the hypothetical Kumta suture close to the KMK granite (Ishwar-Kumar et al, 2013)
The geochronological results from the four cases reported in this paper represent snapshots into the long evolution of the Dharwar Craton

Summary

Introduction

Archean cratons developed progressively by the interplay of two main processes: the gradual accumulation of mafic-ultramafic lithologies extracted from the mantle, and their subsequent reworking and refining into more evolved continental crust. Their evolution was characterized by a distinct cyclicity marked by major orogenic periods with intense magmatism, metamorphism and deformation (e.g., de Wit et al, 1992; Percival et al, 2006). The presently preserved fragments of Archean crust are characterized by distinct histories, which permit their assignment to specific clans of cratons (Bleeker, 2003) These clans consist of crustal fragments presumed to have been parts of originally coherent supercratons before their disruption by later orogenic events. These clans consist of crustal fragments presumed to have been parts of originally coherent supercratons before their disruption by later orogenic events. Bleeker (2003)

Methods

Discussion

Conclusion