Mineralogical and geochemical characterization of a rare ultramafic lamprophyre in the Tandilia belt basement, Río de la Plata Craton, Argentina

► We studied an ultramafic lamprophyre (UML) intruded in the Tandilia basement. ► This rock has minerals with mantle signature (Cr-diopside and phlogopite). ► UML dyke external zone shows deformation and metasomatism with up to 32% volume lost. ► A K-Ar age of 1928 ± 54 Ma on phlogopite was determined for the UML studied dyke. ► Isotopic analyses suggest an enriched mantle source for the UML.