Metamorphic P-T conditions of Late Jurassic rhyolites in the Magallanes fold and thrust belt, Patagonian Andes, Chile

Meta-riolitas foliadas de la Formación Tobífera (Jurásico Superior) forman dos escamas tectónicas en el cinturón de pliegues y mantos de los Andes Patagónicos. Exhiben una foliación milonítica penetrativa desarrollada a escala regional. Exceptuando a porfi - roclastos de cuarzo, la mayor parte de la asociación mineral es de origen metamórfi co. Los minerales sincinemáticos, en las sombras de presión, son similares en composición a aquellos de la matriz. La mineralogía metamórfi ca sugiere una evolución entre unos 3 kbar (aprox. 250 ºC) y unos 7 kbar (aprox. 350 ºC). La naturaleza sincinemática de los minerales permite correlacionarlos con una fase compresional del Cretácico Inferior a medio en la región, que probablemente involucró una subducción dirigida hacia el oeste del sustrato cuasi-oceánico sobre el que se depositó la Formación Tobífera

Géodynamique andine : résumé étendus = Andean geodynamics : extended abstracts

Dans la Cordillère de la côte (Chili central), la série occidentale est constituée de roches détritiques d'âge paléozoïque qui ont subi des conditions métamorphiques maximales à haute pression et basse température. Cependant, elles sont rétromorphosées en faciès schistes verts. Des phengites à haute teneur en silice et des reliques d'amphiboles bleues témoignent de l'épisode haute pression. Ainsi, pour ces épais sédiments détritiques, les nouvelles données confortent l'hypothèse d'un métamorphisme au sein d'un prisme d'accrétion. (Résumé d'auteur

Origin and evolution of Avalonia: evidence from U-Pb and Lu-Hf isotopes in zircon from the Mira terrane, Canada, and the Stavelot-Venn Massif, Belguim

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Variscan Metamorphism

Various segments of Variscan crust are currently exposed in Iberia in response to successive tectonic events during the Variscan orogeny itself and subsequent extensional and compressive events during the Alpine cycle, all accompanied by surface erosion, and collectively contributing to their exhumation. We review the main characteristics and geodynamic contexts of the metamorphic complexes developed in Iberia during the Variscan cycle, which include: (i) LP-HT complexes associated to the Cambrian-Early Ordovician rift stage; (ii) HP-LT complexes associated to subduction; and (iii) syn-to-post-collisional, MP and LP/HT complexes from the hinterland to the foreland fold-and thrust belts. All the above contexts are illustrated with case studies. Finally, a review of Variscan metamorphism in the Pyrenees and Catalan Coastal Ranges, located far away from the Rheic suture is also presented