标题：Geochemical systematics of the Mauranipur-Babina greenstone belt, Bundelkhand Craton, Central India: Insights on Neoarchean mantle plume-arc accretion and crustal evolution
摘要：AbstractThe Neoarchean Bundelkhand greenstone sequences at Mauranipur and Babina areas within the Bundelkhand Gneissic Complex preserve a variety of magmatic rocks such as komatiitic basalts, basalts, felsic volcanic rocks and high-Mg andesites belonging to the Baragaon, Raspahari and Koti Formations. The intrusive and extrusive komatiitic basalts are characterized by low SiO2(39–53 wt.%), high MgO (18–25 wt.%), moderately high Fe2O3(7.1–11.6 wt.%), Al2O3(4.5–12.0 wt.%), and TiO2(0.4–1.23 wt.%) with super to subchondritic (Gd/Yb)Nratios indicating garnet control on the melts. The intrusive komatiitic suite of Ti-enriched and Al-depleted type possesses predominant negative Eu and positive Nb, Ti and Y anomalies. The chemical composition of basalts classifies them into three types with varying SiO2, TiO2, MgO, Fe2O3, Al2O3and CaO. At similar SiO2content of type I and III basalts, the type II basalts show slightly high Al2O3and Fe2O3contents. Significant negative anomalies of Nb, Zr, Hf and Ti, slightly enriched LREE with relatively flat HREE and low ∑REE contents are observed in type I and II basalts. Type III basalts show high Zr/Nb ratios (9.8–10.4), TiO2(1.97–2.04 wt.%), but possess strikingly flat Zr, Hf, Y and Yb and are uncontaminated. Andesites from Agar and Koti have high SiO2(55–64 wt.%), moderate TiO2(0.4–0.7 wt.%), slightly low Al2O3(7–11.9 wt.%), medium to high MgO (3–8 wt.%) and CaO contents (10–17 wt.%). Anomalously high Cr, Co and Ni contents are observed in the Koti rhyolites. Tholeiitic to calc alkaline affinity of mafic-felsic volcanic rocks and basalt–andesite–dacite–rhyolite differentiation indicate a mature arc and thickened crust during the advanced stage of the evolution of Neoarchean Bundelkhand greenstone belt in a convergent tectonic setting where the melts were derived from partial melting of thick basaltic crust metamorphosed to amphibolite-eclogite facies. The trace element systematics suggest the presence of arc-back arc association with varying magnitudes of crust-mantle interaction. La/Sm, La/Ta, Nb/Th, high MgO contents (>20 wt.%), CaO/Al2O3and (Gd/Yb)N > 1 along with the positive Nb anomalies of the komatiite basalts reflect a mantle plume source for their origin contaminated by subduction-metasomatized mantle lithosphere. The overall geochemical signatures of the ultramafic-mafic and felsic volcanic rocks endorse the Neoarchean plume-arc accretion tectonics in the Bundelkhand greenstone belt.Graphical abstractDisplay OmittedHighlights•East-west trending (Mauaranipur-Babina-Dhaura) Bundelkhand Greenstone Belt.•Geochemistry of komatiitic basalts-island arc tholeiitic BADR association.•Crustal growth through Neoarchean plume – back arc-arc accretion in Bundelkhand Craton.•Southward subduction polarity.
