Careón ophiolite, NW Spain: Suprasubduction zone setting for the youngest Rheic Ocean floor

Abstract

The Careon ophiolite (Galicia, NW Iberian MassiO shows litho logical and geochemical features suggestive of an origin in a suprasubduction zone setting. As with other Devonian ophiolites in the European Variscan belt, it was generated within a contracting Rheic Ocean.This setting and the general absence of large Silurian-Devonian volcanic arcs on both of the Rheic Ocean margins strongly suggest that this ocean was closed by intraoceanic subduction directed to the north. This subduction removed the older normal (N) mid-oceanic-ridge basalt (MORB) oceanic lithosphere and gave rise to a limited volume of new suprasubduction zone oceanic lithosphere. The Careon ophiolite is a key element in understanding the evolution of the Rheic Ocean, which was the main oceanic domain that closed during the Paleozoic conver gence of Gondwana and Laurussia, preceding the assembly of Pangea.

Fabric Development in a Middle Devonian Intraoceanic Subduction Regime: The Careón Ophiolite (Northwest Spain)

“…Rheic (for Rhea, one of the Titans and sister of Iapetus in Greek mythology) is the name given to one of the oceanic realms closed during the Paleozoic convergence of Gondwana and Laurussia, preceding the assemblage of Pangea (Stampfli and Borel 2002;Murphy et al 2006;Sá nchez Martínez et al 2007). It is accepted that the Rheic Ocean started opening between the Late Cambrian and Early Ordovician (Cocks and Torsvik 2002;Murphy et al 2006;Arenas et al 2007aArenas et al , 2007b.…”

“…Previous investigations established the origin and the metamorphic and structural evolution of the Careó n unit as a whole (Díaz García et al 1999;Sá nchez Martínez et al 2007). The mineral lineation in both crustal and mantle sections has a persistent east-west attitude (figs.…”

“…Therefore, it is inferred that the conditions for textural development for plagioclase (550ЊC) and hornblende (1600ЊC) occurred before 376 Ma. According to the known history of terrane accretion and continental collision in northwest Iberia (Gó mez Barreiro et al 2006Barreiro et al , 2007bSá nchez Martínez et al 2007;Martínez Catalá n et al 2007), these fabrics would have developed in a precollisional setting within the Rheic Ocean (figs. 2, 15).…”

“…3, 4). These structures are considered intraoceanic thrusts that led to the initial imbrication of the suprasubduction oceanic lithosphere and the formation of metamorphic soles during the closure of the Rheic Ocean (Díaz García et al 1999;Sá nchez Martínez et al 2007). A retrograde stage followed, resulting in low-amphibolite to greenschist facies synkinematic mineral assemblages.…”

The eclogite facies gneisses of the Cabo Ortegal Complex (NW Iberian Massif): Tectonothermal evolution and exhumation model

“…500 Ma) and Devonian (ca. 395 Ma) ages respectively, and they are considered to represent the opening and closure of the Rheic Ocean Arenas et al, 2007;Sánchez Martínez et al, 2007. The basal units represent a section of the most external Gondwanan margin, subducted at ca.…”