Petrochemistry and Sr-Nd isotopes of post-collisional Neoproterozoic (ca. 950 Ma) amphibolite dykes of continental flood basalt affinity from the Simdega area: Implications for the geodynamic evolution of the Chhotanagpur Gneissic Complex, Eastern India

Petrology, geochemistry and U–Pb zircon geochronology of Fe–Ti oxide ore‐bearing mafic sill from Saltora‐Mejia area of Chotanagpur Granite Gneissic Complex, eastern India: Implication for late tectonic emplacement of mafic rock of E‐MORB nature in an orogenic belt

“…It is the only reported Fe–Ti oxide ore‐bearing mafic sill in the entire CGGC. Mafic dykes of similar age have also been reported from SW part of CGGC by Kumar et al, 2022 which are proposed to have emplaced in post‐collision extensional setting during 950 Ma and has dual geochemical character (characters inherited from arc mantle and also character of ashenospheric mantle) which is suggested to have been developed due to interaction of mantle plume and sub‐continental lithospheric mantle. The gabbronorite sill is composed of cumulate plagioclase (andesite‐labradorite), clinopyroxene (diopside), orthopyroxene (hypersthene) as major constituent minerals and amphibole (pargasitic hornblende) as late magmatic mineral with little amount of ilmenite as an accessory mineral. The mafic sill is sub‐alkaline and gabbroic to gabbronoritic in composition and has low Mg#, distinct iron‐enriched tholeiitic nature, slight enrichment in LILE, LREE and slight depletion in HFSE like Nb and Ti. The low Mg# of the gabbronorite rock as well as of the constituting clinopyroxenes possibly suggests derivation of the parent melt from an iron‐enriched mantle source.…”

“…The gabbronorite sill of present study is a rare example of mafic magmatism during the span of 1.0-0.9 Ga. However, a recent study of Kumar et al (2022) has reported presence of amphibolite dykes of continental flood basalt affinity from the Simdega area having a probable age of $950 Ma.…”

“…Therefore, a mixed character of orogenic and anorogenic tectonic settings is found in the equilibrium melt which indicates a transitional nature of the equilibrium melt that was evolved during an orogeny-anorogeny transition phase around 960 Ma might be due to asthenospheric upwelling during late to post-orogenic extensional tectonic environment or post-orogenic arc-plume interaction (Bonin, 2004(Bonin, , 2007Litvinovsky et al, 2011,). Mafic dyke with transitional geochemical character has also been reported from CGGC having an age of 950 Ma (Kumar et al, 2022).…”