A number of dykes and sills have been investigated in the Araç-Boyalı Flysch Basin, a foreland basin formed on the platform of the Sakarya Composite Terrane following the closure of the Intra-Pontide Ocean during the Late Cretaceous – Late Paleocene. The andesitic dyke swarms, characterized by well-developed chilled margins, flow textures and elongated vesicles, intrude the basin sediments, among which massive and pillow lavas, as well as lava and pillow breccias are also found. Major element data plotted on SiO2 indicates plagioclase, pyroxene and biotite fractioation, as well Fe-Ti oxides in the samples, that are andesites and andesitic basalts of calc- alkaline character. Tectono-magmatic discrimination diagrams of lavas as well as the dykes are indicative for destructive plate margin volcanism. Lava and dyke samples display similar patterns in REE and Spider diagrams. A depletion of heavy REE, enrichment of LREE is observed, as well as a marked Nb-Ta trough, characteristic of arc magmas. Based on low Mg numbers, together with low compatible trace element concentrations and low Nb/La ratios, compositions of examined samples might have been modified by assimilation processes. Geochemical characteristics of the volcanic rocks reveal that they are products of continental arc magmatism within the Sakarya Composite Terrane above the N-ward subducting Izmir-Ankara oceanic lithosphere of Neotethys.Similarities in major, minor and trace element geochemistry are in favour of dykes being the feeders of the Eocene lava flows within the Eocene basins that formed as a result of post-collisional extention.

Andesitic dyke swarms in the Araç-Boyalı foredeep basin, N Anatolia: Evidence for Eocene extension

MARRONI, MICHELE;PANDOLFI, LUCA
2013

Abstract

A number of dykes and sills have been investigated in the Araç-Boyalı Flysch Basin, a foreland basin formed on the platform of the Sakarya Composite Terrane following the closure of the Intra-Pontide Ocean during the Late Cretaceous – Late Paleocene. The andesitic dyke swarms, characterized by well-developed chilled margins, flow textures and elongated vesicles, intrude the basin sediments, among which massive and pillow lavas, as well as lava and pillow breccias are also found. Major element data plotted on SiO2 indicates plagioclase, pyroxene and biotite fractioation, as well Fe-Ti oxides in the samples, that are andesites and andesitic basalts of calc- alkaline character. Tectono-magmatic discrimination diagrams of lavas as well as the dykes are indicative for destructive plate margin volcanism. Lava and dyke samples display similar patterns in REE and Spider diagrams. A depletion of heavy REE, enrichment of LREE is observed, as well as a marked Nb-Ta trough, characteristic of arc magmas. Based on low Mg numbers, together with low compatible trace element concentrations and low Nb/La ratios, compositions of examined samples might have been modified by assimilation processes. Geochemical characteristics of the volcanic rocks reveal that they are products of continental arc magmatism within the Sakarya Composite Terrane above the N-ward subducting Izmir-Ankara oceanic lithosphere of Neotethys.Similarities in major, minor and trace element geochemistry are in favour of dykes being the feeders of the Eocene lava flows within the Eocene basins that formed as a result of post-collisional extention.
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Utilizza questo identificativo per citare o creare un link a questo documento: http://hdl.handle.net/11568/235736
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