Abstract The Antarctic Peninsula contains a record of continental-margin volcanism extending from Jurassic to Recent times. Subduction of the Pacific oceanic lithosphere beneath the continental margin developed after Late Jurassic volcanism in Alexander Island that was related to extension of the continental margin. Mesozoic ocean-floor basalts emplaced within the Alexander Island accretionary complex have compositions derived from Pacific mantle. The Antarctic Peninsula volcanic arc was active from about Early Cretaceous times until the Early Miocene. It was affected by hydrothermal alteration, and by regional and contact metamorphism generally of zeolite to prehnite–pumpellyite facies. Distinct geochemical groups recognized within the volcanic rocks suggest varied magma generation processes related to changes in subduction dynamics. The four groups are: calc-alkaline, high-Mg andesitic, adakitic and high-Zr, the last two being described in this arc for the first time. The dominant calc-alkaline group ranges from primitive mafic magmas to rhyolite, and from low- to high-K in composition, and was generated from a mantle wedge with variable depletion. The high-Mg and adakitic rocks indicate periods of melting of the subducting slab and variable equilibration of the melts with mantle. The high-Zr group is interpreted as peralkaline and may have been related to extension of the arc.

Abstract This study presents petrological and geochemical data on Neoarchean granitoids from the northern and central parts of the Bundelkhand Craton to discuss its crustal evolution and tectonic history. The study deals with two granitoid suites, i.e. tonalites–trondhjemites–granodiorites (TTG) and sanukitoids. TTGs are characterized by high SiO 2 , Na 2 O and mostly low to moderate Mg#. They display enrichment in light rare earth elements, low to moderately fractionated heavy rare earth elements (HREE) and low Sr/Y ratios, suggesting their high-HREE character or low-pressure origin from melting of a mafic protolith. The sanukitoid samples show relatively low SiO 2 , high K 2 O (2.1–4.6 wt%), Pb, Sr and Ba, and moderate to low Mg#, Cr, Ni. These granitoids probably generated from partial melting of hydrous mafic rocks followed by interaction with a mantle peridotite. Geochemical characteristics, tectonic discrimination using ratios like (Ce/Pb) PM , (La/Nb) PM and (Th/Nb) PM and regional rock association suggest that the Neoarchean TTGs and sanukitoids were emplaced in a subduction setting. Combining the existing knowledge base, a schematic model for generation and evolution of crust from Paleoarchean to Neoarchean has been proposed for the Bundelkhand Craton.