Faila-arrokak

Faila-arrokak deformazio-mekanismoaren eta deformazio-baldintzen araberakoak izanik, oso informazio baliagarria eman diezagukete. Hori dela eta, lan honetan faila-arroka garrantzitsuen deskribapena eta beraiek sorrarazten dituzten prozesu nagusiak laburbilduko dira

Polyphase tectonic reworking of serpentinites and chlorite-tremolite-talc rocks (SW Spain) from the subduction forearc to intracontinental emplacement

The petrostructural and geochronological study of a poorly known ultramafic unit from SW Spain (Badajoz–Córdoba belt) combined with previous structural data permits disclosure of a history of metasomatism, tectono-metamorphism, reworking and isotopic resetting related to a poly-orogenic evolution in different geodynamic scenarios. The heterogeneous ultramafic unit studied contains antigorite-serpentinites and metasomatized ultramafic rocks (chlorite-talc schists, tremolite-talc-chlorite rocks and magnesio-hornblende-chlorite rocks). Mantle-wedge serpentinization was followed by Si and Al pre- to syn-metamorphic/tectonic metasomatism in a subduction realm. Petrofabrics of selected lithologies reveal variable syn-metamorphic crystal-plastic deformation and recrystallization (assisted by other mechanisms) under relative high pressure, concomitant with the conditions recorded by neighbouring tectonic units that were later intruded by Ordovician granites. The resultant ensemble was reworked and isotopically reset much later in an intracontinental ductile shear zone. Syn- to late-tectonic apatite from chlorite-talc schists provides an anchored Tera–Wassenburg isochron radiometric age of 342.8 ± 12.2 Ma that provides evidence for the decoupling between isotopic systems and microstructures. The results are discussed from a twofold perspective: with regard to the likely tectonic context of this ophiolite (the current analogue of the Mariana forearc) and with regard to regional geological implications.Spanish Ministry of Economy, Industry and Competitiveness and the Fondo Europeo de Desarrollo Regional (MINECO/FEDER CGL2015-63530-P; UPV/EHU (GIU20/010 and GIU15/05)

Masa-espektrometria bidezko prozedura analitiko berrien garapena Geokimika Isotopikoan eta haien aplikazioa presio altuko arroka metamorfikoen azterketan

Geokimika Isotopikoak/Geokronologiak azken hamarkadetan izan duen bilakaerak hainbat teknika analitikoren hobekuntza eragin du, gerriko metamorfikoen tektonikaren gaineko informazioan iraultza eraginez. Euskal Herriko Unibertsitatea (UPV/EHU) berariazko tresneria analitikoaren jabe da, munduan gehien erabiltzen di-ren metodo geokronologikoen inplementazioa eta hobekuntza ahalbidetuz. Lan hone-tan, Rb-Sr eta Lu-Hf sistemak MC-ICP-MS bidez analizatzeko metodologia garatu da alde batetik, eta Hf-Hf eta U-Pb sistemak LA-ICP-MS bidez neurtzeko teknikak beste-tik. Teknika horiek Iberiar mendigunearen ipar-mendebaldeko Malpica-Tui eta Cabo Ortegal Konplexu Aloktonoetako presio altuko arroka metamorfikoen dataziorako eta trazaketarako erabili dira.; The development of Isotope Geochemistry/Geochronology has triggered many technical improvements in the past decades and has revolutionised the potential information available on the tectonics of metamorphic belts. The University of the Basque Country (UPV/EHU) has acquired the specific analytical equipment, which has allowed the implementation and improvement of several of the worldwide most used geochronological methods. In the present work, techniques for Rb-Sr and Lu-Hf analy-sis by MC-ICP-MS, and Hf-Hf and U-Pb analysis by LA-ICP-MS have been devel-oped. These techniques have been employed to date and trace the origin of high-pres-sure rocks from the Malpica-Tui and Cabo Ortegal Allochthonous Complexes of the NW Iberian Massif

Geochemical dataset of high-pressure acid migmatites from the Cabo Ortegal Complex (NW Spain)

This brief note presents geochemical data from rock samples from the Cabo Ortegal Complex (NW Spain). The samples belong to acid lithologies within the mainly basic to intermediate granulite unit that have been poorly investigated so far. For this communication, five samples of the migmatites and an amphibolitic enclave within them have been analysed. The whole-rock major and trace-element analyses were accomplished by means of Q-ICPMS. The dataset provides new and useful information relevant to the origin of the acid migmatites and can be used in addition to information from neighbouring lithologies to enhance understanding of the geological evolution of the Western Variscan Belt

Faila-arrokak

Faila-arrokak deformazio-mekanismoaren eta deformazio-baldintzen araberakoak izanik, oso informazio baliagarria eman diezagukete. Hori dela eta, lan honetan faila-arroka garrantzitsuen deskribapena eta beraiek sorrarazten dituzten prozesu nagusiak laburbilduko dira

Ultramilonitas de apariencia fluidal, pseudotaquilitas o algo intermedio? (Formación Bacariza, Cabo Ortegal)

Occurrence of tectonites with features characteristic of both pseudotachylytes and ultramylonites formed under high-pressure granulite-facies conditions is reported in the Cabo Ortegal Complex of NW Spain. We interpret that these rocks were originated due to a seismic event at great depth (1.4 GPa) under high temperatures (740 ºC). Shear heating would have affected the still hot and mechanically rigid granulites and provoked melt formation. Ambient high P and T would have led to subsequent recrystallization of the previously formed melt giving rise to a weak planar fabric

Deformacion, metamorfismo y exhumacion de las granulitas de alta presion de la Bacariza (Complejo de Cabo Ortega, NO de EspaNa)

Centro de Informacion y Documentacion Cientifica (CINDOC). C/Joaquin Costa, 22. 28002 Madrid. SPAIN / CINDOC - Centro de Informaciòn y Documentaciòn CientìficaSIGLEESSpai