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|Title:||Geochemical systematics of the Mauranipur-Babina greenstone belt, Bundelkhand Craton, Central India: insights on Neoarchean mantle plume-arc accretion and crustal evolution|
Rajanikanta Singh, M.
Chandan Kumar, B.
|Citation:||Geoscience Frontiers, 2018; 9(3):769-788|
|S.P. Singh, K.S.V. Subramanyam, C. Manikyamba, M. Santosh, M. Rajanikanta Singh, B. Chandan Kumar|
|Abstract:||The 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)N ratios 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, Al₂O₃ and CaO. At similar SiO₂ content of type I and III basalts, the type II basalts show slightly high Al₂O₃ and Fe₂O₃ contents. 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/Al₂O₃ and (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.|
|Keywords:||Bundelkhand craton; greenstone belts; mantle dynamics; plume-arc accretion; Neoarchean crustal evolution|
|Rights:||© 2018, China University of Geosciences (Beijing) and Peking University. Production and hosting by Elsevier B.V. This is an open access article under the CC BY-NCND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).|
|Appears in Collections:||Geology & Geophysics publications|
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