An appraisal of geochemical signatures of komatiites from the greenstone belts of Dharwar Craton, India: Implications for temporal transition and Archean upper mantle hydration

Abstract

Archean ultramafic–mafic magmatism associated with dynamic mantle melting processes represents an integral part of crustal evolution and continental growth. Archean mantle plumes and their high temperature derivatives in komatiitic magmas provide a cornerstone in understanding the thermal and chemical evolution of the early Earth and its mantle. In this study, we evaluate the geochemical characteristics of the temporally distinct Sargur Group and Dharwar Supergroup greenstone belts of Dharwar Craton in southern India. The komatiites associated with these greenstone belts are characterized by Al‐depleted and Al‐undepleted compositions. Their MgO, Ni, Co, and Cr concentrations reflect primitive, undifferentiated nature of precursor melts, whereas the HFSE and REE chemistry corroborates high‐degree (30–50%) partial melting of mantle with prominent role of majorite garnet and perovskite in the generation of komatiitic melts. The Al‐depleted komatiites were formed at a greater depth (~13 GPa) by equilibrium melting leaving a garnet‐bearing residue. The resultant komatiitic melt retained buoyancy under extreme pressure and high temperature conditions, segregated and accumulated in the ambient peridotite mantle source and subsequently escaped with progressive decrease in pressure in the ascending plume. The Al‐undepleted and relatively rare Al‐enriched komatiites were derived by fractional melting at intermediate to shallow depths after the discharge of a large proportion of melt ensued by the collapse and entrance of residual garnet into the melt phase. The Mesoarchean–Neoarchean Dharwar komatiites provide evidence for heterogeneous, hydrated Archean upper mantle trapped by ascending mantle plumes. The non‐plume, arc‐related signatures invoke contributions from (a) sub‐cratonic lithospheric mantle roots influenced by ancient subduction events and (b) hydrated Archean upper mantle. The Sargur Group and Dharwar Supergroup komatiites record a distinct temporal transition and geochemical heterogeneity in the Archean mantle beneath the Dharwar Craton and can be attributed to Archean upper mantle hydration by flat slab subduction of >3.3 Ga oceanic crust at shallow level with vestiges of primordial oceanic crust forming deep cratonic mantle roots beneath the Dharwar Craton. The temporal transition towards mantle hydration beneath Dharwar Craton during the Mesoarchean can be correlated with the onset of subduction‐driven plate tectonics and ocean–crust–mantle interactions.

Mafic volcanic rocks of western Iron Ore Group, Singhbhum Craton, eastern India: Geochemical evidence for ocean–continent convergence

“…The origin and evolution of Archean granite‐greenstone belts are subjects of immense interest in understanding the mantle processes, crustal growth, and tectonic evolution of the early Earth. Particularly, the volcanic supracrustals of greenstone belts represent magmatic episodes associated with Precambrian terrane accretion, continental lithosphere evolution and crustal growth through subduction–accretion processes, plume–arc cohabitation, plume–craton interactions, and arc–continent collisions (Barnes & Van Kranendonk, 2014; Dostal & Mueller, 2013; Ganguly, Santosh, & Manikyamba, 2019; Ganguly & Yang, 2018; Ghose & Saha, 2018; Manikyamba et al, 2017; Manikyamba & Kerrich, 2012; Ray et al, 2013; Smithies, Champion, Van Kranendonk, Howard, & Hickman, 2005). Mafic magmatism associated with Precambrian Large Igneous Provinces (LIPs; Mc Call, 2003; Rey, Philippot, & Thebaud, 2003; Sylvester, Campbell, & Bowyer, 1997) as exemplified in Black Range Dyke Swarms in Pilbara Craton, Australia (Heaman, 2008; Wingate, 1999), Mackenzie LIP in northwest Canada (Heaman & LeCheminant, 1993; LeCheminant & Heaman, 1989), Garder Province of southern Greenland (Upton, Emeleus, Heaman, Goodenough, & Finch, 2003) and Dalarna complex in central Scandinavia (Soderlund, Elmings, Ernst, & Schissel, 2006; Suominen, 1991), and numerous Phanerozoic equivalents (Coffin & Eldholm, 1994; Heaman, 2008) are characterized by voluminous magmatic pulses in short durations and giant dyke swarms that served as transport systems for mantle‐derived magmas.…”

Annals of Precambrian Lithospheric Evolution and Metallogeny in the Dharwar Craton, India: Recent Paradigms and Perspectives

“…These studies reflect on the role of plate tectonics during the Paleo-Mesoarchean time frame. Ganguly et al (2019) evaluated the geochemical signatures of komatiites from Mesoarchean Sargur Group and Neoarchean Dharwar Supergroup greenstone belts of Dharwar Craton, corroborated possible proponents for Archean upper mantle hydration and suggested a gradual temporal transition of mantle characteristics during Meso-Neoarchean times. Recently, Pahari et al (2019) have reported U-Pb zircon age and detailed geochemistry of the island arc basalts and Nb-enriched basalts from the Kudremukh greenstone belt of western Dharwar Craton which were erupted at 2498+43 Ma and these are geochemically similar with the Phanerozoic counterparts.…”

Evolution of the Indian subcontinent: Introduction

“…The basal terrestrial deposits also provide insights on the Palaeoarchaean fluvial systems. Ganguly, Santosh , and Manikyamba (—this issue) present an overview of the geochemical features of the Sargur Group and Dharwar Supergroup greenstone belts of the Dharwar Craton in southern India. The Mesoarchean–Neoarchean komatiites in Dharwar provide evidence for heterogeneous, hydrated Archean upper mantle trapped by ascending mantle plumes.…”