Late Variscan (315 Ma) subduction or deceptive zircon REE patterns and U–Pb dates from migmatite‐hosted eclogites? (Montagne Noire, France)

Eclogites hosted in sillimanite-bearing migmatites the Montagne Noire dome (French Massif Central) have an oceanic protolith and recorded a prograde P–T path from ~19.5 kbar, 700°C to pressure peak at ~21 750°C (pseudosection modelling), suggesting metamorphism subduction setting. Subsequent exhumation low-P high-T (LP–HT) conditions (~6 730°C) is constrained by equilibration of embedding migmatite. In samples fresh retrogressed eclogite, all zircon crystals but one display similar REE patterns (no Eu anomaly, flat HREE), usually ascribed crystallization under eclogite-facies conditions. Yet, U–Pb apparent ages both eclogites spread c. 360 Ma dominant data cluster 315 Ma. The 315–310 dates obtained migmatite are interpreted as age partial melt during LP–HT metamorphic stage. First-order geological evidence, particular sedimentary record, excludes existence zone region this period. Unless calling upon major reappraisal tectonics European Variscan orogen, suggests ambiguous relation between population. Various scenarios that could account for observations discussed. Combining our with results previously published Sm–Nd dating garnet, regional considerations, we consider best approximation minimum event. We hypothesize formed farther north were transferred their present location lower-crustal flow. It inferred subsequent exhumation, grains recrystallized underwent total resetting system, whereas system remained mostly unmodified. These caution against use only criterion associate specific HP occurring migmatitic domes.