The Jurassic-Early Cretaceous basalt-chert association in the ophiolites of the Ankara Melange, east of Ankara, Turkey: age and geochemistry

Bortolotti, Valerio
Chiari, Marco
Göncüoğlu, Mehmet Cemal
Principi, Gianfranco
Saccani, Emilio
Tassinari, Renzo
This study is focused on slide blocks including oceanic lavas associated with pelagic sediments within the eastern part of the Ankara Melange. A detailed petrological characterization of the volcanic rocks and a detailed biochronological investigation of the associated radiolarian cherts in eight sections (east of Ankara) was carried out. The volcanic rocks are largely represented by basalts and minor ferrobasalts and trachytes. They show different geochemical affinities and overlapping ages including: (a) Late Jurassic - Early Cretaceous garnet-influenced MORB (middle late Oxfordian to late Kimmeridgian-early Tithonian and early-early late Tithonian; late Valanginian-early Barremian); (b) Early Cretaceous enriched-MORB (middle late Barremian-early early Aptian; Valanginian to middle Aptian-early Albian); (c) Middle Jurassic plume-type MORB (early-middle Bajocian to late Bathonian-early Callovian); (d) Late Jurassic - Early Cretaceous alkaline basalts (middle-late Oxfordian to late Kimmeridgian-early Tithonian; late Valanginian to late Hauterivian). All rock types show a clear garnet signature, as testified to by their high MREE/HREE (middle rare earth element/heavy rare earth element) ratios. The coexistence of chemically different rock types from Middle Jurassic to Early Cretaceous times suggests that they were formed in a mid-ocean ridge setting from partial melting of a highly heterogeneous mantle characterized by the extensive occurrence of OIB-metasomatized portions, which were likely inherited from Triassic mantle plume activity associated with the continental rift and opening of the Neotethys branch.


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The Pontide magmatic belt in the Western Pontides, which developed in response to the northward subduction of the northern branches of the Tethys Ocean, consists of two different volcanic successions separated by an Upper Santonian pelagic limestone unit, the Unaz Formation. The first period of volcanism and associated sedimentation started during the Middle Turonian and lasted until the Early Santonian under the control of an extensional tectonic regime, which created horst-graben topography along the sout...
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The Early Eocene to Early Oligocene tectonic history of the Menderes Massif involves a major regional Barrovian-type metamorphism (M-1, Main Menderes Metamorphism, MMM), present only in the Palaeozoic-Cenozoic metasediments (the so-called "cover" of the massif), which reached upper amphibolite facies with local anatectic melting at structurally lower levels of the cover rocks and gradually decreased southwards to greenschist facies at structurally higher levels. it is not present in the augen gneisses (the ...
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Diverse upper Ladinian to middle Carnian radiolarian faunas have been obtained from different ribbon cherts blocks and tectonic slices of the Izmir-Ankara Suture Complex and the marginal sediments of the Tauride-Anatolide platform within the Bornova Flysch Zone, western Turkey.
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Durukan, Bayram Alper; Bozkurt, Erdin; Department of Geological Engineering (2019)
Structural interpretation of five 2D seismic sections acquired by TPAO is carried out in the Adıyaman region of Southeast Anatolia. The sections are geological calibrated with stratigraphic logs of five boreholes. This study has resulted in the discovery of a previously undefined fault, herein named as Şambayat Fault. The fault is a NW-SEtrending structure that parallels the Bozova Fault and comprises several parallel fault segments. The structural maps of Cretaceous Sayındere and Karababa formations are al...
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Holocene sediments taken from the south-eastern and western Black Sea have been investigated in relation to their geochemical, sedimentological and mineralogical characteristics. Their textures are characterized by their low amount of sand, upward-increasing silt and downward-increasing clay contents. While the terrigenous materials transported from Anatolian volcanic-based sources and European alluvial sediments form the shore deposits, the deep-sea sediments mainly consist of the marine biological product...
Citation Formats
V. Bortolotti et al., “The Jurassic-Early Cretaceous basalt-chert association in the ophiolites of the Ankara Melange, east of Ankara, Turkey: age and geochemistry,” GEOLOGICAL MAGAZINE, pp. 451–478, 2018, Accessed: 00, 2020. [Online]. Available: