Geochemistry and U-Pb-Lu-Hf zircon isotopes of Cu (±Au ± Mo) hosted granitoids of Malanjkhand pluton, Central India: Implications on petrogenesis, source, and crustal evolution

Abstract

The early Paleoproterozoic granitoids (2.45–2.5 Ga) at Malanjkhand and surrounding regions, referred herein to as Malanjkhand granitoids (MG), host Cu (±Mo ± Au) deposit. The MG lie in the south of Central Indian Tectonic Zone (CITZ), forming an integral part of the Bastar Craton. Whole-rock geochemistry, zircon U-Pb-Lu-Hf isotopes of MG are presented with an aim to insight into petrogenesis of MG and its implication on crustal evolution of the Bastar Craton. U-Pb zircon geochronology suggests the formation of MG pluton at least by three felsic magmatic pulses generated at 2.50, 2.47, and 2.45 Ga. Geochemically both the mineralized and unmineralized MG are broadly identical. They bear moderately high Sr/Y and (La/Yb)N similar to as adakite-like melt. However, its typical non-slab-melt (young or old) origin can be predicted. The observed geochemical signatures may result from interactions of mantle-derived mafic melt with a felsic melt derived from pre-existing continental crust. It has been argued that mafic melt is essentially formed by partial melting of slab-melt metasomatised mantle/enriched mantle. Subsequently the mafic melt fractionated to form cumulates. On the other hand, the felsic melt was formed by the melting of Archean continental crust. The observed sub- to ultra-chondritic ɛHf(2.47Ga) zircons (−4.69 to +2.87) and TDMc ages (2.79–3.25 Ga) propound the origin of MG from ancient and juvenile crustal sources. The magmatic pulses (2.45–2.50 Ga) forming the MG and together with synchronous volcano-plutonic complexes from nearby Dongargarh region might have played significant role in rapid crustal growth of Bastar Craton at ~2.5 Ga.