RT Journal Article
T1 Opening and closure of Cadomian peri-Gondwanan oceans: age and evolution of the Mérida Ophiolite (SW Iberia)
A1 Arenas Martín, Ricardo
A1 Rojo-Pérez, Esther
A1 Díez Fernández, Rubén
A1 Albert, R.
A1 Novo Fernández, Irene
A1 Sánchez Martínez, Sonia
A1 Andonaegui Moreno, María Del Pilar
A1 Moreno Martín, Diana
A1 Gerdes, Axel
A1 Garcia Casco, Antonio
AB In the SW Iberian Massif, the Ossa-Morena Complex contains a stack of units of different origin and tectonothermal evolution. Individual terranes of the complex record a Cadomian history, traditionally interpreted in relation to the dynamics of a peri-Gondwanan volcanic arc. The interpretation of the Cadomian terranes is a key issue in the reconstruction of the Ediacaran margin of Gondwana in NW Africa. In the Mérida Massif, a mafic – ultramafic unit stacked between two units of continental or arc affinity is interpreted as a Cadomian ophiolite, the Mérida Ophiolite. Within it, mafic lithologies dated at c. 596 Ma (U-Pb in zircon) have calc-alkaline or tholeiitic affinity, indicating generation in a supra-subduction zone setting. The ophiolite shows a main event of Cadomian metamorphism (c. 590 Ma, U-Pb garnet dating) with a prograde P-T path and peak conditions at c. 700°C and 8 kbar. The mafic rocks show Nd isotopic compositions clearly different from those characteristics of the mafic rocks formed in the axial zone of the volcanic arc. Hence, the Mérida Ophiolite probably represents oceanic lithosphere of a back-arc basin, opened between the volcanic arc and the outer margin of Gondwana. Closure of the back-arc occurred during collision of the volcanic arc with the margin of Gondwana (starting at c. 590 Ma), which caused rapid accretion of the back-arc oceanic lithosphere beneath the arc and prograde metamorphism typical of subduction inception. The Mérida Ophiolite was finally obducted above the continental margin of Gondwana, presently preserved in gneissic unit piled beneath the ophiolite. Cadomian evolution of this peri-Gondwanan arc section continued with new tectonothermal events dated in the range 560–540 Ma that alternated with episodes of intense magmatic activity and preceded the collapse of the magmatic arc and its erosive levelling, followed by the generation of a new episode of intense magmatic activity in the arc and the unconformable deposition of the Ediacaran-Cambrian Malcocinado Formation.
PB Taylor & Francis
SN 0020-6814
YR 2022
FD 2022-10-06
LK https://hdl.handle.net/20.500.14352/72736
UL https://hdl.handle.net/20.500.14352/72736
LA eng
NO Ministerio de Ciencia e Innovación (MICINN)
NO Wilhelm and Else Heraeus  Foundation
NO Deutsche Forschungsgemeinschaft
DS Docta Complutense
RD 13 abr 2025