THE ORIGIN, MINERALOGY AND GEOLOGY OF THE PALEOZOIC KBENTONITES IN TURKIYE

Date

2024-7-26

Author

Yücel, Özge

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K-bentonite layers within the Devonian-Lower Carboniferous Yılanlı Limestone around Bartın area, NW Black Sea region, examined in detail during this study. K-bentonites and their interlayering carbonate rocks (limestone-dolomitic limestone) were collected from Gürgenpınarı and Topluca limestone quarries, near Bartın, NW Türkiye. Mineralogical, petrographical, geochemical and geochronological analyses on those K-bentonite samples were examined. Based on their petrographic microfacies analysis, it is suggested that the examined carbonate rocks were deposited in a shallow marine environment. Illite-rich composition of the examined K-bentonites with lesser smectite contents has been confirmed by XRD analysis. The KI and Ir data of illites remark a high-grade diagenetic origin for the Yılanlı Formation K-bentonites. The age of illite diagenesis has been revealed as (248 ± 6 Ma) Late Permian-Early Triassic for Topluca K-bentonites and (223 Ma ± 6) Late Triassic for Gürgenpınarı K-bentonites by K-Ar dating of illites. The presence of pyrites and pyrrhotites together suggests a diagenetic transformation of sulphide minerals in an anoxic environment. The stable carbon and oxygen isotope data of carbonate rocks indicate that the Topluca and Gürgenpınarı units have a potential for global Kellwasser mass extinction event (Frasnian-Famennian) correlation. Geochemical data indicates an alkali-basaltic mantle source for the original tephra. Based on all the data obtained, it is suggested that the Late Devonian Yılanlı Formation K-bentonites were originated from an alkali-basaltic mantle source, and formed by progressive illitization of original tephra during high grade burial diagenesis in a shallow marine environment.

Subject Keywords

K-bentonites, Late Devonian, Volcanism, Diagenesis, Yılanlı Formation

URI

https://hdl.handle.net/11511/111000

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Graduate School of Natural and Applied Sciences, Thesis