Retroward extrusion of high‐pressure rocks: An example from the Hellenides (Pelion Blueschist Nappe, NW Aegean)

Current tectonic models interpret the Hellenides as a unidirectional, SW‐vergent orogenic belt. New (micro‐)structural and amphibole chemistry analyses show, instead, that the exhumation of the Pelion Blueschist Nappe (PBN) of the Internal Hellenides was achieved by retroward (ENE)‐directed ductile...

Full description

Saved in:
Bibliographic Details
Published in:Terra nova (Oxford, England) England), 2017-12, Vol.29 (6), p.372-381
Main Authors: Gerogiannis, Nikolaos, Xypolias, Paraskevas
Format: Article
Language:English
Subjects:
Basement rock
Basins
Cretaceous
Eocene
Exhumation
Metamorphism
Oligocene
Rock
Rocks
Sedimentary facies
Shear
Subduction
Citations: Items that this one cites
Items that cite this one
Online Access:Get full text
Tags: Add Tag
No Tags, Be the first to tag this record!
Description
Summary:Current tectonic models interpret the Hellenides as a unidirectional, SW‐vergent orogenic belt. New (micro‐)structural and amphibole chemistry analyses show, instead, that the exhumation of the Pelion Blueschist Nappe (PBN) of the Internal Hellenides was achieved by retroward (ENE)‐directed ductile extrusion, which opposes the principal (proward) orogenic vergence. Retroward extrusion occurred between two sub‐parallel, major ductile shear zones (Basal thrust and Upper detachment) with opposite shear senses, which operated simultaneously under blueschist‐ to greenschist‐facies conditions during the late Eocene–Oligocene. Because the PBN is tectonically sandwiched between Pelagonian basement rocks, we suggest that the PBN protolith was accumulated during the Late Cretaceous in an incipient backarc basin developed above the NE‐dipping subduction of the Pindos Ocean beneath the Pelagonian microcontinent. Subsequent Apulian–Pelagonian collision triggered basin inversion and the proward‐dipping intracontinental subduction that caused the early/middle Eocene blueschist‐facies metamorphism followed by the retroward extrusion of the PBN.
ISSN:0954-4879
1365-3121
DOI:10.1111/ter.12297