The Paricutin calc-alkaline lavas: New geochemical and petrogenetic modelling constraints on the crustal assimilation process

Paricutin volcano (1943-1952) is considered as a reference for calc-alkaline suites developed through a process of Assimilation coupled to Fractional Crystallization (AFC). New major and trace element, and Sr-Nd isotope data for the lavas and the application of current petrogenetic modelling tools are used to gather further insight into the magmatic process and to obtain additional information on the evolution of monogenetic volcanoes. Combined major element and Sr-Nd trace element and isotopic ratios AFC modelling suggest that the Paricutin series resulted from the evolution of an initial basaltic andesite (compositionally similar to some olivine-hosted melt inclusions) in a magma reservoir located at km depth. The AFC model supports a continuous process involving the assimilation of up to similar to 35-40% granite-derived melts (with Sr-87/Sr-86 = 0.7085 and Nd-143/Nd-144 = 0.511928) by the initial magma, which crystallized similar to 15% of a mineral assemblage mainly constituted by plagioclase (restricted to the earliest stages) and orthopyroxene, and minor olivine and clinopyroxene, within a temperature range of similar to 1220 degrees C-1100 degrees C. Such high assimilation rates can be explained if the thermal state of the lithosphere was already favourable for melt production at the time of emplacement of the andesitic magma. Under such conditions, crustal assimilation could develop as a syn-eruptive process that allows to explain the relatively higher volumes of less differentiated lavas extruded by the Paricutin volcano as a consequence of its waning activity with time. (C) 2010 Elsevier B.V. All rights reserved.