Early Ordovician orogenic event in Galicia (NW Spain): evidence from U–Pb ages in the uppermost unit of the Ordenes Complex

REE-assisted U–Pb zircon age (SHRIMP) of an anatectic granodiorite: Constraints on the evolution of the A Silva granodiorite, Iberian allochthonous complexes

“…Ages belonging to these two main plutonic bodies (10-TIMS U-Pb in zircon; 499 ± 2 Ma for the Monte Castelo gabbro and 500 ± 2 Ma for the Corredoiras orthogneiss, Abati et al, 1999) confirm that voluminous tholeiitic and cale-alkaline magmatism had a peak at around 500 Ma, and was shortly followed by the development of shear zones. In the basal section of the Monte Castelo gabbro, this shearing was developed under granulite fades conditions and recorded a pressure increase of 2-4 kb .…”

“…The upper unit is tectonically emplaced above the ophiolitic unit and it presents increasing petrological evidence suggesting that it was generated in an arc environment of the Gondwana continental margin (e.g., Abati et al, 1999;Fernandez Suarez et al, 2003;Andonaegui et al, 2002;Puelles et al, 2005). This arc was separated from Gondwana during the Early Ordovidan, starting to drift towards the north at the same time of the opening of the Rheic Ocean Martlnez Catalan et al, 2009).…”

“…In the basal section of the Monte Castelo gabbro, this shearing was developed under granulite fades conditions and recorded a pressure increase of 2-4 kb . The shearing was first indirectly dated using U-Pb in monazites from the host high-grade metasediments that yielded an age between 493 and 498 Ma (Abati et al, 1999 Cross section A-B -----. .e: :.…”

The Corredoiras orthogneiss (NW Iberian Massif): Geochemistry and geochronology of the Paleozoic magmatic suite developed in a peri-Gondwanan arc

“…As the ophiolitic units are considered to represent a colli sional suture sanchez Martinez et al, 2007asanchez Martinez et al, , 2007b, the basal units are interpreted as the most external continen tal margin of Gondwana (Abati et al, 2010;Arenas et al, 1995Arenas et al, , 1997Martinez Catalan et al, 1996;Rodriguez et al, 2003), whereas the upper units represent exotic terranes with Gondwanan affinity. These upper units can be divided in two sets with contrasting pres sure and temperature conditions; on one hand, the high-pressure and high-temperature units (HP-HT), occupying the lower structural position and, on the other hand, the intermediate pressure units (IP) on top of the orogenic pile (Abati et al, 1999Ordofiez Casado et al, 2001).…”

“…The ages of magmatism vary between 520 and 500 Ma (Abati et al, 1999Castifieiras et al, 2010;Fernandez Suarez et al, 2007;Ord6fiez Dsado, 1998;Santos et al, 2002). There are a few studies on the geo chemistry of the igneous rod{s in the HP-HT units (Galan and Marcos, 1997;Gillbarguchi et al, 1990;Mendia Aranguren, 2000) and the mafic rocks in the IP units ; however, no geo chemical study has been carried out nowadays in the felsic rocks from the IP upper units.…”