Fd. Garcia et al., Tectonic evolution of the Careon ophiolite (northwest Spain). A remnant ofoceanic lithosphere in the Variscan belt, J GEOLOGY, 107(5), 1999, pp. 587-605
Analysis of the Careon Unit in the Ordenes Complex (northwest Iberian Massi
f) has supplied relevant data concerning the existence of a Paleozoic ocean
ic lithosphere, probably related to the Rheic realm, and the early subducti
on-related events that were obscured along much of the Variscan belt by sub
sequent collision tectonics. The ophiolite consists of serpentinized harzbu
rgite and dunite in the lower section and a crustal section made up of coar
se-grained and pegmatitic gabbros. An Early Devonian zircon age (395 +/- 2
Ma, U-Pb) was obtained in a leucocratic gabbro. The whole section was intru
ded by numerous diabasic gabbro dikes. Convergence processes took place sho
rtly afterward, giving rise to a mantle-rooted synthetic thrust system, wit
h some coeval igneous activity. Garnet amphibolite, developed in metamorphi
c soles, was found discontinuously attached to the thrust fault. The soles
graded downward to epidote-amphibolite facies metabasite and were partially
retrogressed to greenschist facies conditions. Thermobarometric estimation
s carried out at a metamorphic sole (T approximate to 650 degrees C; P appr
oximate to 11.5 kbar) suggested that imbrications developed in a subduction
setting, and regional geology places this subduction in the context of an
early Variscan accretionary wedge. Subduction and imbrication of oceanic li
thosphere was followed by underthrusting of the Gondwana continental margin
.