Author:
Gómez-Frutos Daniel,Castro Antonio,de la Rosa Jesús
Abstract
AbstractIntermediate magma compositions have been postulated to be parental to Andean-type magmatism in the recent years. Geochemical and experimental methods have allowed the modelling of a hypothetical parental composition that accounts for the major element trends displayed by Andean-type batholiths. However, natural plutonic examples matching the modelled composition remain lacking, likely due to the predominance of fractionated liquids and cumulates in the batholiths after protracted and large-scale differentiation. Contrary to this, magma mingling zones, a common feature in Andean-type batholiths, are characterised by quenching phenomena, minimising differentiation. In this paper, we present data from intermediate magmatism in the world-class Gerena magma mingling zone in the Seville Sierra Norte batholith (southern Iberia), compositionally equivalent to Andean-type magmatic series. Geochemical data from quenched dark globules of variable scale and the corresponding host granodiorites are contrasted with the bimodal trends displayed by the host batholith. Results suggest that the smaller-scale dark globules have not undergone any significant fractionation. Furthermore, after conducting geochemical modelling we conclude the dark globules represent a composition that could be parental to Andean-type magmas. We propose that magma mingling zones are an optimal place to probe for parental magmas of Andean-type magmatism, particularly those represented in pristine melanocratic, intermediate globules.
Funder
Agencia Estatal de Investigación
Publisher
Springer Science and Business Media LLC
Reference58 articles.
1. Gill, J. B. Bulk chemical composition of orogenic andesites. In Orogenic Andesites and Plate Tectonics (ed. Gill, J. B.) 97–167 (Springer, 1981).
2. Alonso-Perez, R., Müntener, O. & Ulmer, P. Igneous garnet and amphibole fractionation in the roots of island arcs: Experimental constraints on andesitic liquids. Contrib. Mineral. Petrol. 157, 541–558 (2009).
3. Carroll, M. R. & Wyllie, P. J. The system tonalite-H2O at 15 kbar and the genesis of calc-alkaline magmas. Am. Mineral. 75, 345–357 (1990).
4. Castro, A. A non-basaltic experimental cotectic array for calc-alkaline batholiths. Lithos 382, 105929 (2021).
5. Grove, T. L., Donnelly-Nolan, J. M. & Housh, T. Magmatic processes that generated the rhyolite of Glass Mountain, Medicine Lake volcano, N. California. Contrib. Mineral. Petrol. 127, 205–223 (1997).