Geochemical characterization and isotopic age of Caradocian magmatism in the northeastern Iberian Peninsula: Insights into the Late Ordovician evolution of the northern Gondwana margin

Abstract

This paper presents new geochronological, geochemical and isotopic data for Late Ordovician magmatism
(455±2 Ma) from the Variscan massifs in the northeastern Iberian Peninsula. This magmatism is mainly
composed of aluminous and metaluminous plutonic rocks and a sequence of calc-alkaline ignimbrites and
epiclastic volcanic rocks, which were deformed and metamorphosed during the Variscan orogeny. The
metaplutonic rocks are located in the lower part of a Neoproterozoic/Early Cambrian metasedimentary
sequence in the Canigó massif (Eastern Pyrenees). Aluminous orthogneisses have isotopic signatures that
indicate a crustal origin, whereas metaluminous orthogneisses originate from a mixture of juvenile and
crustal melts. The metavolcanic rocks define a calc-alkaline ignimbritic sequence of crustal origin located in
the lower part of the Late Ordovician sequence in the Les Gavarres massif (Catalan Coastal Ranges). TDM ages
for all the studied Late Ordovician rocks range from Mesoproterozoic to Paleoproterozoic (1.3 Ga, 1.5 Ga,
1.7 Ga and 2.2 Ga), suggesting a Neoproterozoic crust with Paleoproterozoic components and an arc
signature, as the most probable source for the crustal melts. The isotopic similarities between the studied
samples and other Early Ordovician magmatic rocks of the Central and Western Iberian Massif suggest
repeated melt extractions from a common basement as the source for the Early and Late Ordovician
magmatism in the Iberian realm. However, the studied massifs are more closely linked to other massifs from
the Mediterranean realm. The most probable tectonic setting for the emplacement of the Late Ordovician
volcanic and plutonic bodies is that of an extensional regime, which postdates a previous Ordovician
contractional event and the opening of the Rheic Ocean.