Evolución estructural y cinemática De una corteza continental subducida: la unidad de Malpica-Tui (no del Macizo Ibérico)

[EN] The Variscan belt rose from the collision between Gondwana and Laurussia during the Upper Paleozoic. The basement of the NW Iberian Massif preserves a set of allochthonous units, from which the pre-Variscan evolution of the external margin of Gondwana can be studied and the Variscan history and evolution established. This work is focussed on the outer edge of the Gondwana continent, which in Spain is represented by the basal units of the Galician allochthonous complexes. These units bring an excellent scenario to study the tectonic evolution of the more internal zones of a collisional orogen related to the assembly of a supercontinent, a well-known global event occurring once every several hundred million years. The analysis of the sedimentary record of the Malpica-Tui Unit and part of the basal units of the Órdenes Complex, based on field, petrographic and isotopic (U-Pb in detrital zircons) data has shown the existence of two different stratigraphic sequences. Integrating the new information with the regional background permits to understand the geodynamic evolution of the northern margin of Gondwana during the Late Neoproterozoic and Lower Paleozoic. A model based on structural mapping, combined with microstructural and metamorphic analysis has been developed for the Variscan evolution of the basal units. It includes the subduction of the continental margin of Gondwana, and the subsequent exhumation and emplacement over more internal parts of the margin via ductile thrusts accompanied by recumbent folding. These thrusts were followed by others that transferred the more exotic perigondwanan terranes from Laurussia to Gondwana and then, by the gravitational collapse of the collisional wedge, assisted by extensional detachments and the formation of migmatitic domes which preceded the development of strike-slip shear zones and sub-vertical faulting. Special attention has been paid to the stretching lineations developed during the whole process, which show how the successive deformation phases may control the final macro- and microstructural patterns in the internal zones of an orogenic belt. Based on this analysis, plus the kinematic criteria, the macrostructural evolution and the age populations of detrital zircons used to constrain the paleoposition of the main continental blocks involved in the collision, a protracted component of dextral convergence is suggested for the whole Upper Paleozoic between Gondwana and Laurussia.

Author

• Díez Fernández, Rubén

• Tesis y disertaciones académicas
• Universidad de Salamanca (España)
• Tesis Doctoral
• Academic dissertations
• Geología
• Geology
• Petrología
• Petrology
• Metamorfismo
• Metamorphism (Geology)

Identifier

hdl:10366/108918

OAI identifier oai:identifier

oai:gredos.usal.es:10366/108918