The University of Southampton
University of Southampton Institutional Repository

The petrology of Paleogene volcanism in the Central Sakarya, Nallihan Region: Implications for the initiation and evolution of post-collisional, slab break-off-related magmatic activity

The petrology of Paleogene volcanism in the Central Sakarya, Nallihan Region: Implications for the initiation and evolution of post-collisional, slab break-off-related magmatic activity
The petrology of Paleogene volcanism in the Central Sakarya, Nallihan Region: Implications for the initiation and evolution of post-collisional, slab break-off-related magmatic activity
Zircon ages, mineral chemistry, whole-rock major and trace element compositions, as well as Sr–Nd isotopic ratios of basaltic (basanite, basalt, and hawaiite with MgO = 3.90–10.06 and SiO2 = 43.18–48.16) to andesitic (SiO2 = 50.86–61.27) and rhyolitic (SiO2 = 71.11–71.13) volcanic rocks (E-W emplaced Nall?han volcanics) in the Lower Eocene terrestrial sedimentary units in the Central Sakarya Zone were studied and compared with those of the northerly located E-W-trending Eocene volcanic rocks (the K?zderbent Volcanics with 52.7–38.1 Ma radiometric ages) that are thought to be related to slab break-off process following the continental collision in the NW Anatolia. Zircon U–Pb ages of the Nall?han volcanics vary from 51.7 ± 4.7 to 47.8 ± 2.4 Ma.

Clinopyroxene from the basaltic and andesitic rocks record crystallization conditions from ~ 7–8 kbars (~ 23 km) and ~ 1210 °C, to 4.5–1.5 kbars (~ 14–1.5 km) and 1110–1010 °C crystallization conditions, respectively. The olivine-bearing, high-MgO (up to 10 wt%) basaltic rocks of the Nall?han volcanics have nepheline-normative and Na-alkaline compositions, while the andesitic to rhyolitic rocks show calc-alkaline affinity with mainly sodic character. This is the first time this type of volcanic rock has been described in this region. The initial Sr isotopic ratios of both basaltic and andesitic–rhyolitic samples from the Nall?han volcanics are similar (~ 0.7040–0.7045), indicating that fractional crystallization processes were not accompanied by crustal contamination and that the magma chambers were likely stored within ophiolitic units. Trace element ratios suggest that the Nall?han volcanics were derived from E-MORB- or OIB-like enriched mantle sources, while the K?zderbent volcanics had N-MORB-like depleted mantle sources. Both volcanic units were produced by partial melting of spinel-bearing (shallow) mantle sources that had undergone subduction-related enrichment processes, with the degree of enrichment having been greater for the K?zderbent volcanics.

The geochemical features of both the Nall?han and K?zderbent volcanics are best explained as the result of slab break-off, in which the Nall?han volcanics (located closer to the original subduction front) were produced mainly by the melting of upwelling asthenospheric mantle. Further back from the subduction front, the upwelling interacted with more highly metasomatized sub-arc mantle that underwent partial melting to produce the K?zderbent volcanics. This geodynamic scenario can be used for understanding other post-collisional slab break-off-related magmatic activities.
0024-4937
81-98
Kasapoğlu, Bülent
247842c6-cb73-4c82-a0f6-1ac5bac9ba6a
Ersoy, Yalçın E.
a598a7e6-2043-465e-9207-4993f67a6f92
Uysal, İbrahim
8557da7a-eb5e-47e7-a4fe-583c2ca45e47
Palmer, Martin
d2e60e81-5d6e-4ddb-a243-602537286080
Zack, Thomas
cd23d55e-b75d-4e0b-b2ba-800fab3624ee
Koralay, Ersin O.
2cd553f9-212a-4d98-ba27-0cca6248d18b
Karlsson, Andreas
220ebb2f-c09a-4699-b640-b02ac3c17e3b
Kasapoğlu, Bülent
247842c6-cb73-4c82-a0f6-1ac5bac9ba6a
Ersoy, Yalçın E.
a598a7e6-2043-465e-9207-4993f67a6f92
Uysal, İbrahim
8557da7a-eb5e-47e7-a4fe-583c2ca45e47
Palmer, Martin
d2e60e81-5d6e-4ddb-a243-602537286080
Zack, Thomas
cd23d55e-b75d-4e0b-b2ba-800fab3624ee
Koralay, Ersin O.
2cd553f9-212a-4d98-ba27-0cca6248d18b
Karlsson, Andreas
220ebb2f-c09a-4699-b640-b02ac3c17e3b

Kasapoğlu, Bülent, Ersoy, Yalçın E., Uysal, İbrahim, Palmer, Martin, Zack, Thomas, Koralay, Ersin O. and Karlsson, Andreas (2016) The petrology of Paleogene volcanism in the Central Sakarya, Nallihan Region: Implications for the initiation and evolution of post-collisional, slab break-off-related magmatic activity. Lithos, 246-247, 81-98. (doi:10.1016/j.lithos.2015.12.024).

Record type: Article

Abstract

Zircon ages, mineral chemistry, whole-rock major and trace element compositions, as well as Sr–Nd isotopic ratios of basaltic (basanite, basalt, and hawaiite with MgO = 3.90–10.06 and SiO2 = 43.18–48.16) to andesitic (SiO2 = 50.86–61.27) and rhyolitic (SiO2 = 71.11–71.13) volcanic rocks (E-W emplaced Nall?han volcanics) in the Lower Eocene terrestrial sedimentary units in the Central Sakarya Zone were studied and compared with those of the northerly located E-W-trending Eocene volcanic rocks (the K?zderbent Volcanics with 52.7–38.1 Ma radiometric ages) that are thought to be related to slab break-off process following the continental collision in the NW Anatolia. Zircon U–Pb ages of the Nall?han volcanics vary from 51.7 ± 4.7 to 47.8 ± 2.4 Ma.

Clinopyroxene from the basaltic and andesitic rocks record crystallization conditions from ~ 7–8 kbars (~ 23 km) and ~ 1210 °C, to 4.5–1.5 kbars (~ 14–1.5 km) and 1110–1010 °C crystallization conditions, respectively. The olivine-bearing, high-MgO (up to 10 wt%) basaltic rocks of the Nall?han volcanics have nepheline-normative and Na-alkaline compositions, while the andesitic to rhyolitic rocks show calc-alkaline affinity with mainly sodic character. This is the first time this type of volcanic rock has been described in this region. The initial Sr isotopic ratios of both basaltic and andesitic–rhyolitic samples from the Nall?han volcanics are similar (~ 0.7040–0.7045), indicating that fractional crystallization processes were not accompanied by crustal contamination and that the magma chambers were likely stored within ophiolitic units. Trace element ratios suggest that the Nall?han volcanics were derived from E-MORB- or OIB-like enriched mantle sources, while the K?zderbent volcanics had N-MORB-like depleted mantle sources. Both volcanic units were produced by partial melting of spinel-bearing (shallow) mantle sources that had undergone subduction-related enrichment processes, with the degree of enrichment having been greater for the K?zderbent volcanics.

The geochemical features of both the Nall?han and K?zderbent volcanics are best explained as the result of slab break-off, in which the Nall?han volcanics (located closer to the original subduction front) were produced mainly by the melting of upwelling asthenospheric mantle. Further back from the subduction front, the upwelling interacted with more highly metasomatized sub-arc mantle that underwent partial melting to produce the K?zderbent volcanics. This geodynamic scenario can be used for understanding other post-collisional slab break-off-related magmatic activities.

Full text not available from this repository.

More information

Accepted/In Press date: 29 December 2015
Published date: March 2016
Organisations: Geochemistry

Identifiers

Local EPrints ID: 390904
URI: https://eprints.soton.ac.uk/id/eprint/390904
ISSN: 0024-4937
PURE UUID: 48935467-a51c-4f2d-b082-47a30b485dbc

Catalogue record

Date deposited: 06 Apr 2016 15:36
Last modified: 01 Mar 2019 17:31

Export record

Altmetrics

Contributors

Author: Bülent Kasapoğlu
Author: Yalçın E. Ersoy
Author: İbrahim Uysal
Author: Martin Palmer
Author: Thomas Zack
Author: Ersin O. Koralay
Author: Andreas Karlsson

University divisions

Download statistics

Downloads from ePrints over the past year. Other digital versions may also be available to download e.g. from the publisher's website.

View more statistics

Atom RSS 1.0 RSS 2.0

Contact ePrints Soton: eprints@soton.ac.uk

ePrints Soton supports OAI 2.0 with a base URL of https://eprints.soton.ac.uk/cgi/oai2

This repository has been built using EPrints software, developed at the University of Southampton, but available to everyone to use.

We use cookies to ensure that we give you the best experience on our website. If you continue without changing your settings, we will assume that you are happy to receive cookies on the University of Southampton website.

×