Vestiges of older greenstone in Mesoarchaean Chakradharpur granite gneiss, Singhbhum Craton, India: Implications for plume‐lithosphere interaction at rifted cratonic margin

Abstract

The Chakradharpur granite gneiss (CGG) represents an uplifted Archaean basement within the North Singhbhum Orogen (NSO) of Singhbhum‐Orissa Craton in the eastern Indian shield and shares a Mesoarchaean 3.12 Ga age equivalent to the emplacement of Singhbhum granite (SBG) phase III. The CGG hosts numerous enclaves of tonalitic gneisses, metamorphosed ultramafic and mafic volcanics, metagabbros, metasediments, and conglomerates that collectively represent vestiges of an older greenstone belt preserved within it. The mineralogical composition of the ultramafic volcanic enclaves of CGG has been overprinted by greenschist facies metamorphism presenting a talc‐tremolite‐phlogopite‐actinolite assemblage with prominent development of crenulation cleavage, pressure solutions and relict spinifex texture. These are characterised by restricted low SiO2 (39.7–46.8 wt.%) at consistently high MgO (20.7–28 wt.%) contents, and geochemically classified as: (a) subalkaline (Na2O + K2O < 2) komatiite and meimechite and (b) an alkaline (Na2O + K2O > 2) type picrobasalt‐foidite‐basanite assemblage. Depleted LILE and LREE chemistry, Al2O3/TiO2 versus (Gd/Yb)N and HFSE abundances suggest that the studied Al‐undepleted Munro‐type komatiite and meimechite were derived by high degree (30%–50%), shallow level (<90 km) partial melting of a hot, anhydrous mantle plume carrying depleted components. It is suggested that the komatiite‐meimechite melts were deflected by an Archaean cratonic keel and erupted through thinned continental lithosphere at a rifted cratonic margin. Geochemical evidence of crustal contamination preserved in these komatiites are equated with minor input from reworking of older continental materials and interaction between plume‐derived asthenospheric melts and metasomatized subcontinental lithospheric mantle (SCLM). Zr/Hf, Zr/Sm, Nb/Ta, Zr/Nb, and Nb/Th ratios for the picrobasalt, high Mg basalt, foidite and basanite rocks corroborate their generation through variable degrees of partial melting of a heterogeneous lithospheric mantle source carrying depleted plume‐derived melts and enriched components from metasomatized lithosphere. Mantle processes involved assimilation of metasomatic components of SCLM by ascending melts of plume incubating at the base of lithosphere ensued by melt generation at different mantle depths extending from garnet to spinel peridotite domains. Therefore, the geochemical signatures of ultramafic enclaves in CGG invoke distinct magmatic episodes during plume‐craton interaction, melt generation at thinned craton margin to rifted continental interior and melting of metasomatized continental lithosphere that collectively contributed to the evolution of Archaean mantle lithosphere system, volcanism with diverse chemical compositions and greenstone generation in the Singhbhum Craton.

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.…”

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

“…Precambrian magmatic episodes were associated with diverse tectonic environments including (a) an oceanic plateau association composed of compositionally uniform komatiites and Mg-to Fe-rich tholeiitic basalts erupted from mantle plumes; (b) a compositionally diverse oceanic and continental arc associations, dominated by "normal" tholeiitic to calc-alkaline basalts, andesites, dacites, and rhyolites with boninites, picrites, low-Ti tholeiites, adakites, high-magnesian andesites, and Nb-enriched basalts; and (c) ultramafic-mafic-alkaline lithologies indicating plume magmatism at rifted cratonic margins. These diverse magmatic suites suggest Precambrian terrane accretion, continental lithosphere evolution, and crustal growth through subductionaccretion processes, plume-arc cohabitation, plume-craton interactions, and arc-continent collisions (Barnes & Van Kranendonk, 2014;Dostal & Mueller, 2013;Ganguly & Yang, 2018;Ghose & Saha, 2018;Manikyamba et al, 2017;Manikyamba & Kerrich, 2012;Ray et al, 2013;Smithies, Champion, Van Kranendonk, Howard, & Hickman, 2005).…”