Análisis de la variación del tamaño de grano en las Metabasitas de la Serie de Acebuches (Macizo Ibérico Meridional)

Abstract

A granulometric analysis has been made on the metabasites from the Acebuches series, in the contact between Ossa-Morena and South-Portuguese zones (SW Iberian Massif)- Mean grain sizes, population densities, CSDs and aspect ratios have been calculated. From these, it has been estimated the evolution of the grain size and shape changes across the whole series. Crain size decreases and uniformizes from the top of the series towards the South Iberian Shear Zone (SISZ). In the same sense, the aspect ratio increases (i.e. grains acquire a more elongated habit). These changes are interpreted as due to the superposition of two processes: I) an inverted metamorphic event and 2) the later superposition of the deformation related to the SISZ, which produced retrograde metamorphism and intense mylonitization. At the base of the series, where the deformation related to the SISZ is most intense, the grain size and shape reached a steady state.