Short-duration regional metamorphic event recorded in a Variscan subduction channel (Malpica-Tui eclogites, NW Iberia)

An isotopic resetting event is disclosed at ca. 350 Ma, based on Rb-Sr isotopic analyses (whole rock, garnet, clinopyroxene and phengite fractions) of eclogites with coronitic garnet and planolinear eclogites from the Malpica-Tui Allochthonous Complex (NW Iberia). The eclogites were buried, deformed/recrystallized and subsequently exhumed in a Late Devonian subduction channel. Lu-Hf and Sm-Nd isotopes date a ca. 375-Ma metamorphic peak of the subduction-exhumation cycle that occurred under similar to 2.6 GPa and 610-640 degrees C and was overprinted by the 350-Ma event, which occurred still under high-pressure conditions. The latter resetting is interpreted as a very short-duration regional metamorphic phenomenon recorded by high-pressure rocks in the west European Variscan belt at time scales shorter than those characteristic of orogenic lithosphere in subduction/collision cycles.