Ordovician metamorphism and magmatism preserved in the Ossa Morena Complex: SHRIMP geochronology, geochemistry and Sr[sbnd]Nd isotopic signatures of the Sierra Albarrana Domain (SW Iberian Massif)

Abstract

This study integrates SHRIMP UPb zircon geochronology and whole-rock and SrNd isotope geochemistry data from migmatites and granitic rocks of the Sierra Albarrana Domain. We provide new information on the magmatic and metamorphic events of this domain of the Ossa-Morena Complex. The metasedimentary succession, nowadays corresponding to a migmatite dome, was probably deposited during the Ediacaran and Cambrian. SHRIMP UPb ages of magmatic and zoned metamorphic zircon grains indicate that the main tectono-magmatic event in the Sierra Albarrana Domain is Late Cambrian (granite emplacement; 481.2 ± 2.3 Ma) to early Ordovician (migmatization; 477.8 ± 2.4 Ma), supported by the intrusion of La Cardenchosa Pluton, by the low-pressure partial melting and by the ductile deformation of the host metasedimentary rocks. We suggest that the granitic magmatism, the migmatization and the main regional fabrics are part of a single Ordovician event, only slightly modified by Variscan reworking.Geochemical and isotopic data are compatible with an extensional environment in the middle-upper crustal levels, related to a continental rift development. This setting and timing are compatible with the latest magmatic event of the Early Paleozoic rifting (535–460 Ma), well documented in the Ossa Morena Complex. The geochemical characteristics of the subalkaline rift-related rocks of the Ossa Morena Complex and of the Central Iberian Zone partly coincide. As a result, it is not possible to discriminate between them and favor a correlation between both terranes based on the geochemical affinities of magmatic rocks of similar age.