Assimilation of sialic crustal material by volcanics of the easternmost extension of the Trans-Mexican Volcanic Belt Evidence from Sr and Nd isotopes

Abstract

Pliocene to Quaternary basaltic to rhyolitic volcanics of the easternmost part of the TMVB are characterized by ⁸⁷Sr/⁸⁶Sr ratios from 0.70342 to 0.70511 and ¹⁴³Nd/¹⁴⁴Nd ratios from 0.51250 to 0.51287. Since the volcanics are of Pliocene to Quaternary age, the measured Sr and Nd isotope ratios are taken as initial ratios. These isotope ratios are negatively correlated and, with one exception, plot on the 'mantle array'. The isotopic variation cannot be explained by simple binary mixing models or AFC-modelling. Our interpretation suggests a complex model involving mantle heterogeneities and assimilation of crustal material.