@article{25,
  author = {C Lotout and M Poujol and Pavel Pitra and R Anczkiewicz and J Van Den Driessche},
  title = {From Burial to Exhumation: Emplacement and Metamorphism of Mafic Eclogitic Terranes Constrained Through Multimethod Petrochronology, Case Study from the L{\'e}v{\'e}zou Massif (French Massif Central, Variscan Belt)},
  abstract = {Linking mineral growth and time is required to unravel the evolution of metamorphic rocks. However, dating early metamorphic stages is a challenge due to subsequent retrograde overprinting. A fresh eclogite and a former eclogite retrogressed under amphibolite facies from the southern French Massif Central (L{\'e}v{\'e}zou massif, Variscan belt) were investigated with a large panel of geochronometers (U{\textendash}Pb in zircon, rutile and apatite, Lu{\textendash}Hf and Sm{\textendash}Nd in garnet) in a petrological context tightly constrained by petrographic observations, trace element analyses and phase equilibrium modelling. Both samples recorded similar HP conditions at 18{\textendash}23 kbar and 680{\textendash}800{\textdegree}C, whereas the retrogressed eclogite later equilibrated at 8{\textendash}9{\textperiodcentered}5 kbar and c.600{\textdegree}C. In the retrogressed sample, most of the zircon grains are characterized by negative Eu anomalies and HREE enrichment, and yield an Ordovician U{\textendash}Pb date of 472{\textperiodcentered}3 {\textpm} 1{\textperiodcentered}7 Ma, interpreted as the emplacement age of the mafic protolith. In agreement with other data available for the Variscan belt, and based on zircon trace element record and whole-rock geochemistry, this age is considered to represent the magmatism associated with the extreme thinning of the continental margins during the Ordovician. In the same sample, a few zircon rims show a weaker HREE enrichment and yield a date of 378 {\textpm} 5{\textperiodcentered}7 Ma, interpreted as a prograde pre-eclogitic age. Lu{\textendash}Hf garnet dating from both samples yields identical dates of 357 {\textpm} 13 Ma and 358{\textperiodcentered}0 {\textpm} 1{\textperiodcentered}5 Ma inferred to approximate the age of the high-pressure metamorphic peak. Fresh and retrogressed samples yield respectively 350{\textperiodcentered}4 {\textpm} 7{\textperiodcentered}7 Ma and 352 {\textpm} 20 Ma dates for Sm{\textendash}Nd garnet dating, and 367{\textperiodcentered}8 {\textpm} 9{\textperiodcentered}1 Ma and 354{\textperiodcentered}9 {\textpm} 9{\textperiodcentered}5 Ma for U{\textendash}Pb rutile dating. Apatite grains from the retrogressed sample give a mean age of 351{\textperiodcentered}8 {\textpm} 2{\textperiodcentered}8 Ma. The similarity between all recorded ages from distinct chronometers and radiometric methods (U{\textendash}Pb, rutile, apatite; Lu{\textendash}Hf, garnet; Sm{\textendash}Nd, garnet) combined with P{\textendash}T estimations from high-pressure metamorphic rocks equilibrated under different conditions testifies to very fast processes that occurred during the Variscan orogeny, highlighting a major decompression of 15{\textendash}8{\textperiodcentered}5 kbar in less than 7 Myr, and suggesting mean exhumation rates in excess of 6{\textperiodcentered}3 mm/yr.},
  year = {2020},
  booktitle = {Journal of Petrology},
  journal = {Journal of Petrology},
  series = {Journal of Petrology},
  volume = {61},
  month = {04},
  issn = {0022-3530},
  url = {https://doi.org/10.1093/petrology/egaa046},
  doi = {10.1093/petrology/egaa046},
}