A plume- mantle interaction model for the petrogenesis of komatiite- komatiitic basalt- basalt- basaltic andesite volcanism from the Paleoarchean (3.57-3.31 Ga) Iron Ore Group greenstone belts, Singhbhum craton, India: Constraints from trace element geochemistry and Sm-Nd geochronology

The Paleoarchean Singhbhum craton greenstone belts comprise basalt, interbedded minor komatiite (both alumina depleted and undepleted, ADK and AUK, respectively), komatiitc basalt, dacite and chert grouped as (-3.57 Ga) southern Iron Ore Group (S-IOG, Daitari samples) and - 3.31 Ga eastern Iron Ore Group (E-IOG, Dabanki samples). Considering the importance of metabasalt in formation of TTG batholiths, modeling their petrogenesis from mantle sources and Sm-Nd geochronology was conducted. The rocks resemble Archean nonarc greenstone basalt (Nb/Th = 3.61-10.3) with tholeiitic affinity. The ADK of S-IOG was modeled by 37% partial melting of garnet lherzolite, komatiitic basalt was derived from ADK magma by -25% assimilation fractional crystallization (AFC) and - 16% AFC of this magma formed tholeiitic basalt. Derived from depleted parental magmas they yield an isochron age of 3573 +/- 63 Ma (2SD), Ndi = 0.50810 +/- 0.00008, MSWD = 0.59 (n = 10) and epsilon Nd (3573 Ma) = +2.03 +/- 0.03. Dacite formation, modeled by mixing of melts between Eoarchean felsic crust and metabasalt, yielded an isochron age of 3507 +/- 180 Ma (2SD), Ndi = 0.50800 +/- 0.00015, MSWD = 0.15 (n = 11), epsilon Nd (3507 Ma) = -1.46 +/- 1.71; ca. 3.8-3.9 Ga Nd TDM model ages indicate vestiges of Eoarchean crust. The AUK of E-IOG was modeled by -45% partial melting and ADK by -33% melting of garnet lherzolite mantle. About 32% AFC of primary ADK magma formed the komatiitic basalt that evolved to tholeiitc basalt magma (-24%) which on -15% AFC evolved to basaltic andesite - andesite magma. Derived from depleted parental magmas, the E-IOG rocks yielded an isochron age of 3313 +/- 110 Ma (2SD), Ndi = 0.50847 +/- 0.00013, MSWD = 0.06 (n = 10), epsilon Nd (3313 Ma) = +2.62 +/- 0.28. Petrogenesis of Paleoarchean greenstone non-arc basaltic volcanism and associated komatiite can be best explained by plume-mantle interaction and partial melting of ambient mantle followed by assimilation fractional crystallization of parental magmas, and does not preclude recycling of pre-existing crust.

Automated summary

The Paleoarchean Singhbhum craton greenstone belts are composed of various rocks formed through different processes such as partial melting, assimilation fractional crystallization, and magma mixing, mostly derived from metamorphosed parental magmas. Further investigation indicates an association with plume-mantle interaction and partial melting, suggesting possible recycling of pre-existing crust during these processes.