Arc crust formation of Lesser Antilles revealed by crustal xenoliths from Petit St. Vincent

Abstract The Lesser Antilles volcanic arc is known for its magmatic diversity and unusually abundant plutonic xenoliths. Xenoliths from Petit St. Vincent (Grenadines’ archipelago) are particularly interesting because of their textural petrogenetic range. Here we combine petrographic observations, Electron Backscatter Diffraction (EBSD) analysis, major trace element chemistry xenoliths lavas geochemical thermal modelling to explore the construction crust beneath Vincent. dominated by calcic plagioclase, clinopyroxene amphibole, can be divided into two main categories, igneous meta-igneous. Igneous typically have cumulate textures; meta-igneous range texturally those that preserve vestiges primary fabrics intensely deformed varieties characterised grain-size reduction foliation development. Meta-igneous also contain most plagioclase (An98–100). presence both provides evidence reworking older antecedent intrusions. latter a protolith composition similar high-MgO, low-Sr picrites high-Ca, high-Sr ankaramites neighbouring islands Petite Martinique Grenada. derive older, mafic present at onset subduction. Trace EBSD analyses consistent with complex history re-melting deformation mediated chlorine-bearing H2O rich fluids (including melts). Thermal supports crustal through repeated magma intrusions indicates observed structure thickness could developed on timescale approximately 4 million years rates compatible regional flux. Based thermodynamic models exhumed ancient sections, Collins et al. (Nature Geoscience, 13, 331–338, 2020) proposed water-fluxed melting may an important aspect deep sections world-wide. Textures mineralogy Vincent, including characteristic high-An testify such process active, intra-oceanicarc.