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

Author(s)

Benjamin Huet, Loic Labrousse, Patrick Monié, Benjamin Malvoisin, Laurent Jolivet

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.

Organisation(s)

Department of Geology

External organisation(s)

Université Montpellier 2, Université de Lausanne, Université Paris VI - Pierre-et-Marie-Curie, Institut des Sciences de la Terre d'Orléans (ISTO)

Journal

Geological Magazine

Volume

152

Pages

711-727

No. of pages

17

ISSN

0016-7568

DOI

https://doi.org/10.1017/S0016756814000661

Publication date

07-2015

Peer reviewed

Yes

Austrian Fields of Science 2012

105124 Tectonics

Keywords

ASJC Scopus subject areas

Geology

Portal url

https://ucrisportal.univie.ac.at/en/publications/coupled-phengite-40ar39ar-geochronology-and-thermobarometry-ptt-evolution-of-andros-island-cyclades-greece(8e04a89a-0fab-4059-b4fb-8e1437d34997).html