Earth and Planetary Science Letters 474 (2017) 215–225 Contents lists available at ScienceDirect Earth and Planetary Science Letters www.elsevier.com/locate/epsl Age of UHP metamorphism in the Western Mediterranean: Insight from rutile and minute zircon inclusions in a diamond-bearing garnet megacryst (Edough Massif, NE Algeria) Olivier Bruguier a,∗ , Delphine Bosch a , Renaud Caby a , Alberto Vitale-Brovarone b , Laure Fernandez a , Dalila Hammor c , Rabah Laouar c , Aziouz Ouabadi d , Nachida Abdallah d , Mehdi Mechati c a Géosciences Montpellier, Université de Montpellier, UMR-CNRS 5243, Place E. Bataillon, 34095 Montpellier cedex 5, France b Institut de Minéralogie, de Physique des Matériaux, et de Cosmochimie (IMPMC), Sorbonne Universités – UPMC Univ Paris 06, UMR CNRS 7590, Muséum National d’Histoire Naturelle, IRD UMR 206, 4 Place Jussieu, 75005 Paris, France c Laboratoire de Recherche Géologie, Faculté des Sciences de la Terre, Université Badji Mokhtar, BP 12, Annaba 23000, Algeria d USTHB, Bab Ezzouar, Laboratoire de Géodynamique, Géologie de l’Ingénieur et Planétologie (LGGIP/FSTGAT), Algiers, Algeria a r t i c l e i n f o a b s t r a c t Article history: Received 26 March 2017 Received in revised form 23 June 2017 Accepted 26 June 2017 Available online 14 July 2017 Editor: F. Moynier Keywords: UHP metamorphism Western Mediterranean U–Pb dating zircon rutile Diamond-bearing UHP metamorphic rocks witness for subduction of lithospheric slabs into the mantle and their return to shallow levels. In this study we present U–Pb and trace elements analyses of zircon and rutile inclusions from a diamond-bearing garnet megacryst collected in a mélange unit exposed on the northern margin of Africa (Edough Massif, NE Algeria). Large rutile crystals (up to 300 μm in size) analyzed in situ provide a U–Pb age of 32.4 ± 3.3 Ma interpreted as dating the prograde to peak subduction stage of the mafic protolith. Trace element analyses of minute zircons (≤30 μm) indicate that they formed in equilibrium with the garnet megacryst at a temperature of 740–810 °C, most likely during HP retrograde metamorphism. U–Pb analyses provide a significantly younger age of 20.7 ± 2.3 Ma attributed to exhumation of the UHP units. This study allows bracketing the age of UHP metamorphism in the Western Mediterranean Orogen to the Oligocene/early Miocene, thus unambiguously relating UHP metamorphism to the Alpine history. Exhumation of these UHP units is coeval with the counterclockwise rotation of the Corsica–Sardinia block and most likely resulted from subduction rollback that was driven by slab pull.  2017 Elsevier B.V. All rights reserved. 1. Introduction A paradigm in Earth Sciences has long been buoyancy of the continental crust. The discovery of coesite and metamorphic dia- monds (Chopin, 1984; Smith, 1984; Sobolev and Shatsky, 1990), the hallmark of ultra-high pressure (UHP) metamorphism, in con- tinental crust units demonstrated however that the latter can be subducted deep down into the mantle (>100 km assuming only a lithostatic pressure) where these minerals formed before to be subsequently returned to shallow levels. Although tomographic studies leave no doubts that entire slabs can be buried down to the 660 km deep discontinuity (e.g. Fukao et al., 2009), exhumed UHP units of oceanic origin are paradoxically more scarce. * Corresponding author. E-mail address: bruguier@gm.univ-montp2.fr (O. Bruguier). In the Western Mediterranean Orogen (WMO), evidence for crustal rocks affected by UHP metamorphism are restricted to only few areas in the Betic-Rif orocline (Ruiz-Cruz and Sanz de Galdeano, 2013a, 2013b) and more recently in the Maghrebides (Caby et al., 2014). The timing of UHP metamorphism in the WMO is however still the matter of controversy, with two alternatives corresponding to the two last main orogenic events that have af- fected this area, i.e. Hercynian or Alpine. This controversy mainly stems from the lack of firm geochronological determinations on UHP metamorphic units. Unraveling the age of UHP metamorphism in the WMO is therefore paramount to every model describing the formation and geodynamic evolution of this area. In this article, we investigate the timing of UHP metamorphism recorded by mineral inclusions (rutile and zircon) in a diamond- bearing garnet megacryst from the Edough Massif of northeastern Algeria (Fig. 1), which has been the focus of a recent geochemical study (Caby et al., 2014). http://dx.doi.org/10.1016/j.epsl.2017.06.043 0012-821X/ 2017 Elsevier B.V. All rights reserved.