Coupled phengite 40Ar–39Ar geochronology and thermobarometry: P-T-t evolution of Andros Island (Cyclades, Greece)

Abstract : Andros is a key island for understanding both the timing of high-pressure–low-temperature (HP-LT) metamorphism and the dynamics of crustal-scale detachment systems exhuming high-grade units in the Cyclades (Greece). Using phengite 40Ar–39Ar geochronology coupled with thermobarometry, as well as data from literature, we constrain the pressure–temperature–time (P-T-t) paths of the Makrotantalon and Attic–Cycladic Blueschist units on Andros. Peak conditions of the HP-LT episode in the Makrotantalon unit are 550 °C and 18.5 kbar, dated at 116 Ma. We correlate this episode with Early Cretaceous blueschist facies metamorphism recognized in the Pelagonian zone of continental Greece. This is a new argument favouring a Pelagonian origin for the Makrotantalon unit. In the Attic– Cycladic Blueschist unit, the P-T-t path is characterized by: (1) exhumation after peak conditions in HP-LT conditions between 55 and 35 Ma; (2) isobaric heating at 7 kbar until 30 Ma; and (3) isothermal decompression until 21 Ma. This thermal evolution and timing are similar to those of the neighbouring Tinos Island, emphasizing major thermal re-equilibration at the transition between stable and retreating subduction. Modifications of the crustal thermal state played a major role in the evolution of the North Cycladic Detachment System, below which Andros HP-LT units were exhumed.
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Submitted on : Tuesday, February 10, 2015 - 11:14:44 AM
Last modification on : Wednesday, May 15, 2019 - 3:57:43 AM

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Benjamin Huet, Loic Labrousse, Patrick Monié, Benjamin Malvoisin, Laurent Jolivet. Coupled phengite 40Ar–39Ar geochronology and thermobarometry: P-T-t evolution of Andros Island (Cyclades, Greece). Geological Magazine, Cambridge University Press (CUP), 2015, 152 (4), pp.711-727. ⟨10.1017/S0016756814000661⟩. ⟨insu-01114909⟩

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