Ophiolites of different Paleozoic ages occur in North-West (NW) Iberia in a rootless suture representing the remnants of the Rheic Ocean, Associated allochthonous terranes in the hanging-and foot-walls of the suture derive from the former margins.whereas the relative autochthon corresponds to the Paleozoic passive margin of northern Gondwana, The Paleozoic tectonic evolution of this part of the circum-Atlantic region is deduced from the stratigraphical. petrological. structural and metamorphic evolution of the different units and their ages. The tectonic reconstruction covers from Cambro-Ordovician continental rifting and the opening of the Rheic Ocean to its Middle to Upper Devonian closure. Then, the Variscan Laurussia-Gondwana convergence and collision is briefly described, from its onset to the late stages of collapse associated with the demise of the orogenic roots. ResumeUne suture sans racines et la perte des racines d'une cha'ine montagneuse : la cha'ine varisque du Nord-Ouest de I'Iberie. Des ophiolites d'ages differents affieurent dans le Nord-Ouest de l'Iberie dans une suture sans racines. temoin de l'ocean * Corresponding author.E-mail address: jrmc @usal.es (J.R. Martfnez Catahin).RhMque. Les terrains allochtones sur et sous la suture derivent de ses deux rnarges, tandis que I' autochtone relatif appartient a la marge passive du Nord de Gondwana. On peut deduire l'evolution des plaques dans cetle partie de la region circum-Atlantique it partir des dounees stratigraphiques, petrologiques, structurales, metarnorphiques et geochronologiques. Celte evolution inc1ut le developpernent d'un rift continental et l'ouverture de l'ocean Rhe'ique pendant le Carnbro-Ordovicien ainsi que sa ferrneture au Devonien rnoyen a superieur. On decrit aussi I' evolution de la convergence et collision varisque entre Laurussia et Gondwana, du debut jusqu'aux demiers stades d'un effondrernent associe a la perte des racines orogeniques.Keywords: Oceanic suture; Rheic Ocean; Variscan evolution; N\V IberiaMots des : Suture oceanique ; Ocean Rhelque ; Evolution varisque ; Nord-Ouest de l'Iberie IntrodnctionThe North-West (NW) of the Iberian Massif is located at the hinge zone of the Ibero-Armorican Arc ( Fig. 1) and preserves relicts of oceanic domains that once separated the Paleozoic continents [50,51]. A suture occurring in the hanging-wall of a large thrust system is rootless, which makes its interpretation difficult. However, the excellent exposure of the ophiolitic and associated allochthonous terranes permits the establishment of a sequence of emplacement, crosscutting relationships, and metamorphic gradients.In the absence of continental-scale strike-slip shear zones and faults, the Galician-northeru Portugal section is retrodeformable, permitting qualitative palinspastic reconstructions of the Gondwana-Laurussia conver gence. These characteristics make of NW Iberia a key site to uuravel the history of the Paleozoic plate evolution of the circum-Atlantic region, and specially that of the Rheic Ocean. This contrib...
A correlation between allochthonous units exposed in the NW Iberian Massif and the southern Armorican Massif is carried out based on lithological associations, structural position, age and geochemistry of protoliths and tectonometamorphic evolution. The units on both sides of the Bay of Biscay are grouped into Upper, Middle and Lower allochthons, whereas an underlying allochthonous thrust sheet identified in both massifs is referred to as the Parautochthon. The Lower Allochthon represents a fragment of the outermost edge of Gondwana that underwent continental subduction shortly after the closure of a Palaeozoic ocean which, in turn, is represented by the Middle Allochthon. The latter consists of supra-subduction ophiolites and metasedimentary sequences alternating with basic, mid-ocean ridge basalt (MORB)-type volcanics, with inheritances suggesting the proximity of a continental domain. Seafloor spreading began at the Cambro-Ordovician boundary and oceanic crust was still formed during the Late Devonian, covering the lifetime of the Rheic Ocean, which is possibly represented by the Middle Allochthon. The opening of the oceanic domain was related to pulling apart the peri-Gondwanan continental magmatic arc, which is represented by the Upper Allochthon.
The Malpica-Tui Unit (Galicia, NW Spain) records eclogite-and blueschist-facies metamorphism during the onset of the Variscan orogeny in Europe. Petrological analysis involving pseudo sections calculated using THERMOCALC shows that the Upper Sheet of this unit, the Cean Schists, recorded a three pseudo sections together with petrographic 0 bservations is then necessary to estimate the real oxidation state of the rocks and correctly evaluate the P-T conditions.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.