Upper Ordovician magmatism in the Central Pyrenees: First U-Pb zircon age from the Pallaresa Massif

Abstract

Ordovician geodynamics: The Sardic Phase in the Pyrenees, Mouthoumet and Montagne Noire massifs International Meeting (2017. Figueras, España)The Late Ordovician magmatism is well represented in all massifs of the Eastern Pyrenees and the Catalan Coastal Ranges, which contain Upper Ordovician rocks. Nevertheless, data about this magmatic episode in the Central Pyrenees are scarce. This work shows the first geochronological data for Upper Ordovician magmatism in the Pallaresa massif. This massif is a large E-W trend antiformal structure included in the metamorphic structural units of the Pyrenean Axial Zone, where Cambro-Ordovician and Upper Ordovician rocks crop out. The Cambro-Ordovician rocks consist of a low-grade monotonous alternation of quartzites and slates with some limestone and conglomerate intercalations, which show evidence of a pre-Variscan penetrative deformation. The Upper Ordovician succession lies unconformably on the older Cambro-Ordovician beds and is represented by a siliciclastic succession with an intermediate limestone level. Volcanic rock levels have been observed interbedded within what was considered a Cambro-Ordovician succession close to outcrops of Upper Ordovician rocks in the eastern part of Pallaresa massif. Both metasedimentary and volcanic rocks were deformed and metamorphosed during the Variscan Orogeny.The volcanic rocks are rhyodacitic to dacitic crystal-rich meta-tuffs with a pervasive foliation. Their mineralogical composition is mainly volcanic quartz, feldspar and biotite. The matrix consists of fine grained of biotite, muscovite, quartz and clinozoisite, the latter mainly developed in highly deformed bands. In addition to these mineral phases, idiomorphic crystals of zircon are recognized.Instituto Geológico y Minero de España, EspañaDepartamento de Geología, Universidad de Oviedo, EspañaPeer reviewe