Eocene mafic volcanism in northern Anatolia: Its causes and mantle sources in the absence of active subduction

Şafak Altunkaynak*, Yildirim Dilek

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

42 Citations (Scopus)

Abstract

Eocene mafic volcanic rocks occurring in an E-W-trending, curvilinear belt along and north of the Izmir-Ankara-Erzincan suture zone (IAESZ) in northern Anatolia, Turkey, represent a discrete episode of magmatism following a series of early Cenozoic collisions between Eurasia and the Gondwana-derived microcontinents. Based on our new geochronological, geochemical, and isotope data from the Kartepe volcanic units in northwest Anatolia and the extant data in the literature, we evaluate the petrogenetic evolution, mantle melt sources, and possible causes of this Eocene volcanism. The Kartepe volcanic rocks and spatially associated dikes range from basalt and basaltic andesite to trachybasalt and basaltic trachyandesite in composition, and display calc-alkaline and transitional calc-alkaline to tholeiitic geochemical affinities. They are slightly to moderately enriched in large ion lithophile (LILE) and light rare earth elements (LREE) with respect to high-field strength elements (HFSE) and show negative Nb, Ta, and Ti anomalies reminiscent of subduction-influenced magmatic rocks. The analysed rocks have 87Sr/86Sr(i) values between 0.70570 and 0.70399, positive εNd values between 2.7 and 6.6, and Pb isotope ratios of 206Pb/204Pb(i) = 18.6-18.7, 207Pb/204Pb(i) = 15.6-15.7, and 208Pb/204Pb(i) = 38.7-39.1. The 40Ar/39Ar cooling ages of 52.7 ±0.5 and 41.7 ±0.3 Ma obtained from basaltic andesite and basalt samples indicate middle to late Eocene timing of this volcanic episode in northwest Anatolia. Calculated two-stage Nd depleted mantle model (TDM) ages of the Eocene mafic lavas range from 0.6 to 0.3 Ga, falling between the TDM ages of the K-enriched subcontinental lithospheric mantle of the Sakarya Continent (1.0-0.9 Ga) to the north, and the young depleted mantle beneath central Western Anatolia (0.4-0.25 Ga) to the south. These geochemical and isotopic features collectively point to the interaction of melts derived from a sublithospheric, MORB-like mantle and a subduction-metasomatized, subcontinental lithospheric mantle during the evolution of the Eocene mafic volcanism. We infer triggering of partial melting by asthenospheric upwelling beneath the suture zone in the absence of active subduction in the Northern Neotethys. The geochemical signature of the volcanic rocks changed from subduction-and collision-related to intra-plate affinities through time, indicating an increased asthenospheric melt input in the later stages of Eocene volcanism, accompanied by extensional deformation and rifting.

Original languageEnglish
Pages (from-to)1641-1659
Number of pages19
JournalInternational Geology Review
Volume55
Issue number13
DOIs
Publication statusPublished - 2013

Funding

This study was supported in part by research grants ITU-BAP Project (No: 36125) and TÜBİTAK-ÇAYDAG (Project No: 110Y351), and Miami University Distinguished Professor Discretionary Funds. We thank our students Alp Ünal and Ömer Kamacı for their help in the field. Our work on Eocene magmatism in the Tethyan orogenic belt has benefited from our discussions with S.L. Chung, N. Imamverdiyev, H. Jamali, Y. Kadioglu, X.-X. Mo, Y. Yilmaz, and D.-C. Zhu.

FundersFunder number
ITU-BAP36125
TÜBİTAK-ÇAYDAG110Y351
University of Miami

    Keywords

    • Asthenospheric melt
    • Eocene volcanism in Anatolia
    • Postcollisional magmatism
    • Slab breakoff
    • Subduction-metasomatized mantle

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