RT Journal Article
T1 The eclogite facies gneisses of the Cabo Ortegal Complex(NW Iberian Massif): Tectonothermal evolution andexhumation model
A1 Albert Roper, Richard
A1 Arenas Martín, Ricardo
A1 Sánchez Martínez, Sonia
A1 Gerdes, Axel
AB The tectonothermal evolution of the eclogite facies gneisses of the Cabo Ortegal Complex has been investigated using new fieldand petrologic studies. This gneissic unit is included in the high-pressure and high-temperature (HP-HT) upper units of the allochthonouscomplexes of NW Iberia, a Cambrian arc-derived peri-Gondwanan terrane emplaced above ophiolitic units considered torepresent the Rheic Ocean suture. Two detailed cross-sections performed in excellent exposures on the Cantabrian coast allows aclear understanding of the lithological constitution and deformations affecting the unit. The eclogitic gneiss unit is constituted bymetasedimentary gneisses with abundant mafic inclusions, felsic rocks and rare ultramafic inclusions. The felsic rocks range fromcentimetric leucosomes to metric bodies and most of them were generated during extensive partial melting affecting the unit. Thefirst tectonic fabric detected in the unit is a rarely preserved S1 foliation developed during subduction (ca. 400-390 Ma; 22 kbar). Adrastic and fast exhumation (ca. 390 Ma; 12-10 kbar) generated a regional mylonitic foliation which represents the most prominentstructural feature in the HP-HT upper units. The consecutive generation of extensional detachments, recumbent folds and a basalthrust occurred during the change from continental-type subduction to the underthrusting of ophiolitic units. These consecutivestructures are probably related and the consequence of a long and pronounced exhumation of the subducted complex. The tectonothermalevolution of the eclogite facies gneisses of the Cabo Ortegal Complex represents an illustrative example of the intricatehistory of these deeply subducted units, which are relatively frequent in the suture zone of the Variscan Belt. It is important to remarkthat the structural, metamorphic and geochronological patterns in the evolution of this gneissic unit follows almost perfectly the predictions based in numerical experiments about the exhumation of ultra-high-P complexes. Consequently it represents a directconfirmation of these models.
PB Universidad Complutense de Madrid
SN 1698-6180
YR 2012
FD 2012
LK https://hdl.handle.net/20.500.14352/44359
UL https://hdl.handle.net/20.500.14352/44359
LA eng
DS Docta Complutense
RD 7 jun 2025