Paleoarchean partial convective overturn in the Singhbhum Craton, Eastern India

摘要: Abstract Analyses of fold superposition structures and kinematics shear zones along a 120 km long E–W corridor across the Singhbhum Craton (Eastern India) are combined with U–Pb–Th chemical ages texturally constrained monazites in supracrustals, gneisses granitoids to reconstruct Paleoarchean tectonic history western part Craton. Metamorphic sub-greenschist facies shallow marine platformal sediments Iron Ore Group (IOG) accordantly deformed Jagnnathpur meta-lavas were accreted onto basement composed >3.4 Ga amphibolite para-amphibolites/quartzites/muscovite schists (Older Group, OMG) anatectic Older Tonalite Gneisses (OMTG). Crustal shortening was followed by emplacement-ascent granitoid pluton, SGP (3.2–3.3 Ga) synchronous sinking supracrustal screens N/NNE-trending steep-dipping sinistral–normal ductile zones. Deformation microstructures indicate bulk pluton responded exhumation-strain low- T (≤500 °C) flow quartz K-feldspar, plagioclase being largely unaffected. But margin emplaced concurrent westward-retreating exhumation thickened crust at  ≥ 650 °C. Since all share same fabric, microstructural features imply phased emplacement during strain. The transition from crustal interrupted between 3.2 3.4 Ga is explained two-stage partial convective overturn model involving typical supracrustal-down, granitoid-up sense movement. restoration new complements growing evidence that accretion may have operated Paleoarchean.