Imperial College London
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Dr Valentin LAURENT

Faculty of Engineering, Department of Earth Science & Engineering

Senior Teaching Fellow in Pedagogic Transformation
 
 
 
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Contact

 

v.laurent

 
 
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Location

 

Royal School of MinesSouth Kensington Campus

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Summary

 

Publications

Citation

BibTex format

@article{Laurent:2021:10.1016/j.gca.2021.06.001,
author = {Laurent, V and Scaillet, S and Jolivet, L and Augier, R and Roche, V},
doi = {10.1016/j.gca.2021.06.001},
journal = {Geochimica et Cosmochimica Acta},
pages = {141--173},
title = {<sup>40</sup>Ar behaviour and exhumation dynamics in a subduction channel from multi-scale <sup>40</sup>Ar/<sup>39</sup>Ar systematics in phengite},
url = {http://dx.doi.org/10.1016/j.gca.2021.06.001},
volume = {311},
year = {2021}
}
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RIS format (EndNote, RefMan)

TY  - JOUR
AB  - The behaviour of the phengite 40Ar/39Ar system has been explored at different scales on Sifnos and Syros, two key islands of the Upper Cycladic Blueschist system (UCB). These islands expose well-preserved eclogites and blueschists that were exhumed via extensional collapse of the Aegean subduction/accretionary wedge during the Eocene and Miocene. Both islands record the switch from convergence to extension via a nappe-scale thermal-kinematic reworking marked by a sharp (~2 km thick) metamorphic transition from preserved high-pressure low-temperature (HP/LT) eclogites and blueschists at the top of the stack (peak P-T conditions of 22 ± 2 kbar and 550 ± 25 °C), to retrogressed greenschists at the base (overprinted at P-T conditions of 12–10 kbar and 500-450 °C). Extensive mapping of regional- to grain-scale 40Ar/39Ar age variations along this gradient reveals that phengite ages consistently decrease from 51 Ma down to 18 Ma towards the base of the stack, in parallel with progressive strain localization during exhumation and reworking by the regional greenschist ductile overprint. Homogeneous grain-scale Ar distributions are recorded in the poorly deformed topmost HP samples as Eocene (51–37 Ma) plateau ages and homogeneous in situ UV ablation ages, and by Miocene (20–18 Ma) plateaus in the intensely deformed basal greenschist samples. The homogeneous eclogite and blueschist ages are interpreted to record protracted crystallization in the subduction channel between 51 and 37 Ma, while the homogeneous basal ages likely record complete resetting and/or neocrystallization at 20–18 Ma. All intermediate samples across the metamorphic transition display variably complex age spectra and discordant in situ ages. Sub-grain scale Ar disequilibrium is ubiquitous in the form of within-sample and within-grain variations, with in situ (1 mm) variations locally encompassing almost the entire age span recorded regionally (up to 26 Myr). T
AU  - Laurent,V
AU  - Scaillet,S
AU  - Jolivet,L
AU  - Augier,R
AU  - Roche,V
DO  - 10.1016/j.gca.2021.06.001
EP  - 173
PY  - 2021///
SN  - 0016-7037
SP  - 141
TI  - <sup>40</sup>Ar behaviour and exhumation dynamics in a subduction channel from multi-scale <sup>40</sup>Ar/<sup>39</sup>Ar systematics in phengite
T2  - Geochimica et Cosmochimica Acta
UR  - http://dx.doi.org/10.1016/j.gca.2021.06.001
VL  - 311
ER  -
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