Large-volume and swift magmatic response to Late Cenozoic segmentation of the subducted Neotethyan oceanic slab: evidence from the Galatian Volcanic Province, northwestern Turkey

ABSTRACT

The Miocene Galatian Volcanic Province (GVP) is one of the largest volcanic provinces in central-western Anatolia, with an extent of ~ 8,900 km². The volcanic activity is extended from 22.5 to 7.5 Ma. The volcanic compositions straddle the alkaline-subalkaline fields, from basic to acid compositions and mostly transitional to sodic affinity. Major oxides show good correlation with SiO₂ indicating prolonged effects of fractional crystallization. Primitive mantle-normalized multi-element patterns indicate overall similarities among the different samples of the three geographic sectors, sharing strong negative anomalies in Nb–Ta–Ti, strong positive peaks at Cs and K, coupled with a common, albeit not always present, positive anomaly at Pb. Mineral-melt geothermobarometric estimates indicates ~1070–1235°C and ~7–19 kbar for melting conditions of basaltic compositions and ~1000–1150°C and ~3–12 kbar for andesitic-dacitic rocks. The absence of correlation between radiogenic isotopes and SiO₂ and MgO is here interpreted as consequence of assimilation-fractional-crystalization processes involving lower continental crust as contaminant. The GVP parental magmas are generated from ~2% to 10% partial melting of a lherzolitic mantle with high spinel/garnet ratio based on intra-REE fractionation constraints. The subduction-related metasomatism inferred for the GVP mantle sources based on their chemistry is interpreted to be linked to the northward subduction of the northern branch of the Neo-Tethys slab. Successive slab retreat resulted in extension for the critical stress distribution through the Cyprus slab, favouring magma propagation for the GVP volcanic region. The eventual break-off of the slab after the continent-continent collision of Arabian and Eurasian plates could have caused a toroidal mantle flow, favouring the widely distributed 15–16 Ma alkaline magmatism in the eastern GVP, associated with passive hot asthenospheric upwelling imaged by teleseismic P-wave tomography.

GRAPHICAL ABSTRACT

KEYWORDS:

• Cenozoic volcanism
• galatian
• segmentation
• mantle
• asthenospheric upwelling

Acknowledgment

This study was supported by funds from Eskisehir Osmangazi University (Project Numbers: 201815A203, 202015D10, 201715A215, 201715031, FCD-2023-2795, FHD-2023-2784, FYL-2022-2482. The authors thank the editorial work of Robert J. Stern as well as the review of two anonymous reviewers, which greatly improved the quality of the manuscript.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Supplementary material

Supplemental data for this article can be accessed online at https://doi.org/10.1080/00206814.2024.2333003

Correction Statement

This article has been corrected with minor changes. These changes do not impact the academic content of the article.

Additional information

Funding

This study was supported by funds from Eskisehir Osmangazi University (Project Numbers: 201815A203, 202015D10, 201715A215, 201715031, FCD-2023-2795, FHD-2023-2784, FYL-2022-2482).