Congratulations to team member Jürgen von Raumer for his latest paper on the Central Iberian basement-A multiphase evolution.
The Cambro‐Ordovician rhyodacitic to dacitic volcanics from the Central Iberian basement, currently known as Ollo‐de‐Sapo (toads eye), have been reported as a specific group of felsic porphyritic rocks with blue quartz and large phenocrysts of K‐feldspar, in a partly vitreous or fine‐grained matrix. Interpreted to form Cambro‐Ordovician volcanic domes, they are accompanied by tuffs, ignimbrites and products of reworking in a near‐surface environment.Read More
The coarse‐ to fine‐grained rocks exhibit rather large K‐feldspar phenocrysts, plagioclase and rounded blue quartz, representing former corroded phenocrysts. Their colouration indicates unmixing of TiO2 at around 900 °C during cooling from relatively high crystallisation temperatures, indicating their origin at hot lower crustal conditions. We propose at least a two‐step evolution (1) starting around 495 Ma in the lower crust of a collapsing cordillera, generating a phenocryst‐rich mush and adiabatic melting of the lower crustal protolith to produce the spectacular Ollo‐de‐Sapo porphyrites, before (2) magma ascent and crustal extension leading to a different thermal regime around 483 Ma. This article is protected by copyright. All rights reserved.
Ollo de Sapo Cambro-Ordovician volcanics from the Central Iberian basement-A multiphase evolution.