Eastern Dharwar Craton, India: Continental lithosphere growth by accretion of diverse plume and arc terranes

Greenstone belts of the eastern Dharwar Craton, India are reinterpreted as composite tectonostratigraphic terranes of accreted plume-derived and convergent margin-derived magmatic sequences based on new high-precision elemental data. The former are dominated by a komatiite plus Mg-tholeiitic basalt volcanic association, with deep water siliciclastic and banded iron formation (BIF) sedimentary rocks. Plumes melted at <90 km under thin rifted continental lithosphere to preserve intraoceanic and continental margin aspects. Associated alkaline basalts record subduction-recycling of Mesoarchean oceanic crust, incubated in the asthenosphere, and erupted coevally with Mg basalts from a heterogeneous mantle plume. Together, komatiites-Mg basalts-alkaline basalts plot along the Phanerozoic mantle array in Th/Yb versus Nb/Yb coordinate space, representing zoned plumes, establishing that these reservoirs were present in the Neoarchean mantle.Convergent margin magmatic associations are dominated by tholeiitic to calc-alkaline basalts compositionally similar to recent intraoceanic arcs. As well, boninitic flows sourced in extremely depleted mantle are present, and the association of arc basalts with Mg-andesites-Nb enriched basalts-adakites documented from Cenozoic arcs characterized by subduction of young (<20 Ma), hot, oceanic lithosphere. Consequently, Cenozoic style “hot” subduction was operating in the Neoarchean. These diverse volcanic associations were assembled to give composite terranes in a subduction-accretion orogen at ∼2.7 Ga, coevally with a global accretionary orogen at ∼2.7 Ga, and associated orogenic gold mineralization.Archean lithospheric mantle, distinctive in being thick, refractory, and buoyant, formed complementary to the accreted plume and convergent margin terranes, as migrating arcs captured thick plume-plateaus, and the refractory, low density, residue of plume melting coupled with accreted imbricated plume-arc crust.

Graphical abstractFigure optionsDownload full-size imageDownload as PowerPoint slideHighlights► Greenstone belts of the eastern Dharwar Craton, India, are composite tectonostratigraphic terranes. ► They have diverse volcanic plume- and arc-associations ∼2.7 Ga. ► They were assembled in a subduction-accretion orogen as migrating arcs captured thick plume-plateaus.