Abstract
Abstract. Oceanic rocks in the Ankara Mélange along the Izmir–Ankara–Erzincan suture zone (IAESZ) in north-central Anatolia include locally coherent ophiolite complexes (~ 179 Ma and ~ 80 Ma), seamount or oceanic plateau volcanic units with pelagic and reefal limestones (96.6 ± 1.8 Ma), metamorphic rocks with ages of 256.9 ± 8.0 Ma, 187.4 ± 3.7 Ma, 158.4 ± 4.2 Ma, and 83.5 ± 1.2 Ma indicating northern Tethys during the late Paleozoic through Cretaceous, and subalkaline to alkaline volcanic and plutonic rocks of an island arc origin (~ 67–63 Ma). All but the arc rocks occur in a shale–graywacke and/or serpentinite matrix, and are deformed by south-vergent thrust faults and folds that developed in the middle to late Eocene due to continental collisions in the region. Ophiolitic volcanic rocks have mid-ocean ridge (MORB) and island arc tholeiite (IAT) affinities showing moderate to significant large ion lithophile elements (LILE) enrichment and depletion in Nb, Hf, Ti, Y and Yb, which indicate the influence of subduction-derived fluids in their melt evolution. Seamount/oceanic plateau basalts show ocean island basalt (OIB) affinities. The arc-related volcanic rocks, lamprophyric dikes and syenodioritic plutons exhibit high-K shoshonitic to medium- to high-K calc-alkaline compositions with strong enrichment in LILE, rare earth elements (REE) and Pb, and initial εNd values between +1.3 and +1.7. Subalkaline arc volcanic units occur in the northern part of the mélange, whereas the younger alkaline volcanic rocks and intrusions (lamprophyre dikes and syenodioritic plutons) in the southern part. The late Permian, Early to Late Jurassic, and Late Cretaceous amphibole-epidote schist, epidote-actinolite, epidote-chlorite and epidote-glaucophane schists represent the metamorphic units formed in a subduction channel in the northern Neotethys. The Middle to Upper Triassic neritic limestones spatially associated with the seamount volcanic rocks indicate that the northern Neotethys was an open ocean with its MORB-type oceanic lithosphere by the early Triassic (or earlier). The latest Cretaceous–early Paleocene island arc volcanic, dike and plutonic rocks with subalkaline to alkaline geochemical affinities represent intraoceanic magmatism that developed on and across the subduction–accretion complex above a N-dipping, southward-rolling subducted lithospheric slab within the northern Neotethys. The Ankara Mélange thus exhibits the record of ~ 120–130 million years of oceanic magmatism in geological history of the northern Neotethys.
Highlights
In the circum-Mediterranean mountain chains belonging to the Alpine-Himalayan system, subduction-related tectonic mélanges during pre-collisional stages are described, but they generally are overprinted by arc–continent and continent–continent collisions (Festa et al, 2010 and references therein)
The subduction–accretion complex represented by the Ankara Mélange contains blocks of oceanic lithosphere, showing geochemical affinities ranging from MORB to island arc tholeiite (IAT)
As illustrated in the 143Nd/144Nd vs. 87Sr/86Sr diagram (Fig. 19a), six lamprophyre samples plot on the mantle array, defining a subduction component during the evolution of their magmas. We show in this diagram, for comparison, the Late Cretaceous–early Tertiary volcanic rocks from the southern part of central Anatolia and the eastern Pontides, and the Cenozoic volcanic units in western Anatolia (Alpaslan et al, 2004; 2006; Eyüboglu, 2010; Altunkaynak and Dilek, 2006 and references therein)
Summary
In the circum-Mediterranean mountain chains belonging to the Alpine-Himalayan system, subduction-related tectonic mélanges during pre-collisional stages are described, but they generally are overprinted by arc–continent and continent–continent collisions (Festa et al, 2010 and references therein). In northern Turkey, the 2600-km-long IAESZ extends from west to east, connecting the Vardar suture in the west and the Sevan-Akera suture zone in the east. The ophiolitic mélanges and ophiolite slabs are observed along this zone. At the central part of IAESZ, in the vicinity of Ankara, Kırıkkale, Çankırıand Çorum, the Ankara Mélange, first described by Bailey and McCallien (1950), is a wellknown subduction–accretion type mélange of the world. They defined metamorphic, limestone and ophiolitic rock blocks in era age from Paleozoic to Mesozoic in the mélange
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
