74 / 352
that progressively reached the collision zone as
the basin shrank (Lower Ophiolitic Units). Fi-
nally, further convergence led to a new collision
with another section of the Gondwanan margin,
with generation of a second HP-LIT belt at
c.
370
Ma (Basal Units). Convergence continued during
the Carboniferous and produced the complex in-
tracontinental deformation that characterizes the
Variscan Belt. According to structural data and
paleogeographic reconstructions for the alloch-
thonous pile of NW Iberia, the Devonian and
Carboniferous convergence was accompanied by
a dextral lateral component for most of the time.
Based on modern analogues of continental inter-
action, the development of complex collisions,
as here suggested for Gondwana and Laurussia
during the assembly of Pangea, could have been
the rule rather than the exception throughout
Earth history.
Acknowledgements
Financial support has been provided by the
Spanish project CGL2012-34618 (Ministerio de
Economía y Competitividad).
Many of the ideas developed in this work
emerged during years of stimulating and friendly
discussions with our colleague Florentino Díaz
García, who sadly passed away. This paper is a
tribute to his memory.
References
Ábalos, B. 1997. Omphacite fabric variation in the Cabo
Ortegal eclogite (NW Spain): relationships with strain
symmetry during high-pressure deformation. Journal of
Structural Geology, 19, 621-637.
Ábalos, B., Mendia, M., Gil Ibarguchi, J.I. 1994. Structure
of the Cabo Ortegal eclogite-facies zone (NW Iberia).
Comptes Rendus de l’Académie des sciences de Paris,
319, 1231-1238.
Ábalos, B., Azcárraga, J., Gil Ibarguchi, J.I., Mendia, M.,
Santos Zalduegui, J.F. 1996. Flow stress, strain rate and
effective viscosity evaluation in a high-pressure nappe
(Cabo Ortegal, Spain). Journal of Metamorphic Geology,
14, 227-248.
Ábalos, B., Puelles, P., Gil Ibarguchi, J.I. 2003. Structural as-
semblage of high-pressure mantle and crustal rocks in a
subduction channel (Cabo Ortegal, NW Spain). Tecton-
ics, 22, 1006, TC001405.
Abati, J. 2002. Petrología Metamórfica y Geocronología de
la unidad culminante del Complejo de Órdenes en la
región de Carballo (Galicia, NW del Macizo Ibérico).
Nova Terra, 20, 269 p.
Abati, J., Dunning, G.R., Arenas, R., Díaz García, F.,
González Cuadra, P., Martínez Catalán, J.R., Andonae-
gui, P. 1999. Early Ordovician orogenic event in Galicia
(NW Spain): evidence from U-Pb ages in the uppermost
unit of the Ordenes Complex. Earth and Planetary Sci-
ence Letters, 165, 213-228.
Abati, J., Dunning, G.R. 2002. Edad U-Pb en monacitas y
rutilos de los paragneises de la Unidad de Agualada
(Complejo de Órdenes, NW del Macizo Ibérico). Geo-
gaceta, 32, 95-98.
Abati, J., Arenas, R., Martínez Catalán, J.R., Díaz García,
F. 2003. Anticlockwise
P-T
path of granulites from the
Monte Castelo Gabbro (Órdenes Complex, NW Spain).
Journal of Petrology, 44, 305-327.
Abati, J., Castiñeiras, P., Arenas, R., Fernández-Suárez, J.,
Gómez-Barreiro, J., Wooden, J. 2007. Using SHRIMP
zircon dating to unravel tectonothermal events in arc
environments. The early Palaeozoic arc of NW Iberia re-
visited. Terra Nova, 19, 432-439.
Abati, J., Gerdes, A., Fernández-Suárez, J., Arenas, R.,
Whitehouse, M.J., Díez Fernández, R. 2010. Magmatism
and early-Variscan continental subduction in the north-
ern Gondwana margin recorded in zircons from the
basal units of Galicia, NW Spain. Geological Society of
America Bulletin, 122, 219-235.
Albert, R., Arenas, R., Sánchez Martínez, S., Gerdes, A.
2012. The eclogite facies gneisses of the Cabo Ortegal
Complex (NW Iberian Massif): Tectonothermal evolu-
tion and exhumation model. Journal of Iberian Geology,
38, 389-406.
Albert, R., Arenas, R., Gerdes, A., Sánchez Martínez, S.
2013. Refined ages of magmatism and high-P metamor-
phism in the eclogite facies gneissic formation of the
Cabo Ortegal Complex. Proceedings of the Joint Con-
ference of the Czech and German geological societies:
Crustal evolution and geodynamic processes in Central
Europe. Pilsen, Czech Republic. p. 93.
Albert, R., Arenas, R., Gerdes, A., Sánchez Martínez, S.,
Fernández-Suárez, J., Fuenlabrada, J.M. 2015. Prove-
nance of the Variscan Upper Allochthon (Cabo Ortegal
Complex, NW Iberian Massif). Gondwana Research. (In
press).
dx.doi.org/10.1016/j.gr.2014.10.016.Albert, R., Arenas, R. Gerdes, A., Sánchez Martínez, S. Sub-
mitted. Provenance of the high-P and high-T unit of the
Cabo Ortegal Complex (NW Iberian Massif). Submitted.
Alcock, J., Arenas, R., Martínez Catalán, J.R. 2005. Shear
stress in subducting continental margin from high-pres-
sure, moderate-temperature metamorphism in the
58
3. GEOLOGICAL FRAMEWORK