The Alboran domain in the western Mediterranean evolution: the birth of a concept

Abstract

Since the early 70's the majority of tectonic reconstructions of the western Mediterranean employ the Alboran domain notion as a migrating microcontinent or landmass mainly composed of Paleozoic-Triassic rocks affected by 'Alpine' HP-LT metamorphism. For nearly three decades, since the mid-80's, the Alboran domain was considered as a fragment of the Alpine chain that moved westward, colliding into Iberia and North Africa to produce the Gibraltar arc and Betic-Rif chain. In 2012, a new hypothesis for the evolution of the western Mediterranean was presented in which the Betic-Rif orogenic chain originates from rollback of an initially SE-dipping subduction of the westernmost segments of the Ligurian-Tethys under the Africa margin. This interpretation considers the metamorphic 'Alboran domain' rocks as crustal successions of the hyper-extended African and Iberian continental margins, which have undergone a complete subduction-exhumation cycle above a NW-to W-retreating subduction. A key outcome of this hypothesis is that the Alboran domain is not a fragment of the Alpine chain but a consequence of rollback dynamics.In this contribution we try to elucidate the historical reasons behind the classical 'Alpine' interpretation of the Betic-Rif, by briefly describing key contributions, which appear linked in a logical sequence that traces the evolution of the Alboran domain concept since its original formulation by Andrieux and coauthors in 1971. Le domaine d'Alboran dans l'évolution de la Méditerranée occidentale : la naissance d'un conceptMots-clés. -Orogène Bétique-Rif, Arc de Gibraltar, Apennins, Aperçu historique, Evolution géodynamique.Résumé. -Depuis le début des années 70 la majorité des reconstructions tectoniques de la Méditerranée occidentale dé-finissent le domaine d'Alboran comme un microcontinent ou une masse continentale principalement composée de roches paléozoïques et triasiques affectées par un métamorphisme « alpin » HP-BT. Durant près de trois décennies, depuis le milieu des années 80, le domaine d'Alboran était considéré comme un fragment de la chaîne alpine qui s'était dépla-cé vers l'ouest et était entré en collision avec l'Ibérie et l'Afrique du Nord pour former l'arc de Gibraltar et la chaîne bé-tique-Rif. En 2012, une hypothèse nouvelle a été présentée pour l'évolution de la Méditerranée occidentale, pour laquelle la chaîne bétique-Rif proviendrait du retrait d'une subduction des segments les plus occidentaux de la Tethys ligure plongeant initialement vers le SE sous la marge africaine. Cette interprétation considère les roches métamorphiques du « domaine d'Alboran » comme des séries crustales des marges continentales africaine et ibérique hyper-amincies et ayant subi un cycle complet de subduction-exhumation au-dessus d'une subduction en retrait en direction NW-W. Un résultat clef de cette hypothèse est que le domaine d'Alboran n'est pas un fragment de la chaîne alpine mais une consé-quence d'une dynamique de retrait. Dans cette contribution nous tentons d'élucider les raisons historiques derriè...

Opposite Subduction Polarity in Adjacent Plate Segments

“…The Betic-Rif and the Tell chains and their metamorphic complexes are located at opposed margins in the western Mediterranean, showing opposite tectonic vergences, and separated by the Alboran and the Algerian back arc basins, respectively. According to Vergés and Fernàndez (2012) and Casciello et al (2015) the slabs retreated in opposite directions and passed each other before reaching the upper-lower mantle boundary. Subduction and related mantle flow produce changes in the rock fabric that results in a complex seismic anisotropy pattern that depends on depth, amount of subduction, slab geometry, trench displacement, and consequent mantle flow (e.g., Di Leo et al, 2014;Faccenda & Capitanio, 2013).…”

Crust and mantle lithospheric structure of the Iberian Peninsula deduced from potential field modeling and thermal analysis

“…1 and 2). The hinterland of this arcuate compressive belt is cut by the extensional system related to the back-arc Alboran basin development (see reviews in Doblas et al, 2007;Vergés andCasciello et al, 2015).…”

From the North-Iberian Margin to the Alboran Basin: A lithosphere geo-transect across the Iberian Plate

“…The southern margin of Iberia underwent a complex tectonic evolution about which there is a very active debate (e.g., Carminati et al, 2012;Casciello et al, 2015;Faccena et al, 2004;Rosenbaum and Lister, 2002;Spakman and Wortel, 2004;van Hinsbergen et al, 2014;Vergés and Fernàndez, 2012). According to Vergés and Fernàndez (2012) and Casciello et al (2015), the Betic-Rif orogen was formed as a consequence of SE-dipping subduction of the Ligurian-Tethys lithosphere beneath Africa from Late Cretaceous to middle Oligocene, followed by a fast NW and W retreating slab roll-back.…”

“…According to Vergés and Fernàndez (2012) and Casciello et al (2015), the Betic-Rif orogen was formed as a consequence of SE-dipping subduction of the Ligurian-Tethys lithosphere beneath Africa from Late Cretaceous to middle Oligocene, followed by a fast NW and W retreating slab roll-back. In the Algerian domain, the subduction of the Ligurian-Tethys lithosphere dipped towards the NW, and the SE-and E-directed retreating produced the opening of the Valencia Trough, the Algerian Basin, and the Tyrrhenian Sea.…”