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. The Sobrado unit, within the upper part of the Ordenes Complex (NWSpain) represents an allochthonous tectonic slice of exhumed high-grademetamorphic rocks formed during a complex sequence of orogenic processes inthe middle to lower crust. In order to constrain those processes, U–Pbgeochronology and rare-earth element (REE) analyses of accessory minerals in migmatiticparagneiss (monazite, zircon) and mylonitic amphibolites (titanite) wereconducted using laser ablationsplit stream inductively coupled plasma mass spectrometry (LASS-ICP-MS). The youngest metamorphic zircon age obtainedcoincides with a Middle Devonian concordia monazite age ( ∼380  Ma)and is interpreted to represent the minimum age of the Sobrado high-Pgranulite facies metamorphism that occurred during the early stages of theVariscan orogeny. Metamorphic titanite from the mylonitic amphibolitesyield a Late Devonian age ( ∼365  Ma) and track the progressiveexhumation of the Sobrado unit. In zircon, cathodoluminescence images andREE analyses allow two aliquots with different origins in the paragneiss tobe distinguished. An Early Ordovician age ( ∼490  Ma) wasobtained for metamorphic zircons, although with a large dispersion, relatedto the evolution of the rock. This age is considered to mark the onset ofgranulite facies metamorphism in the Sobrado unit under intermediate-Pconditions, and related to intrusive magmatism and coeval burial in amagmatic arc setting. A maximum depositional age for the Sobrado unit isestablished in the late Cambrian ( ∼511  Ma). The zircondataset also record several inherited populations. The youngest cogeneticset of zircons yields crystallization ages of 546 and 526 Ma which are thoughtto be related to the peri-Gondwanan magmatic arc. The additional presence ofinherited zircons older than 1000 Ma is interpreted as suggesting a WestAfrican Craton provenance.

solid earth

Unraveling the origins and P-T-t evolution of the allochthonous Sobrado unit (Órdenes Complex, NW Spain) using combined U–Pb titanite, monazite and zircon geochronology and rare-earth element (REE) geochemistry