Abstract
The Eastern Caucasus Mountains in Georgia include products from extensive Miocene volcanic activity that are being unraveled by geological mapping supported by geochronology and geochemistry. This article presents new zircon U–Pb geochronology and whole rock geochemistry of the volcanic ash layers of the intermountain Neogene basin of the Eastern Caucasus. Our investigation in the region demonstrates that these ash layers, whose eruption center(s) have not been identified yet, has age and geochemical characteristics of the Mtkvari (Kura) ignimbrite of the Samtskhe-Javakheti volcanic highland. This study shows that zircons from both formations crystallized at the same time ~ 7.50 Ma ago and have geochemical and morphological similarity. Taken together with the geography of the region (200–300 km from the volcanic source to the sedimentary basins), it is likely that the source of the ash layers was the Upper Miocene volcanic eruptions on the Samtskhe-Javakheti volcanic highlands. Based on the distribution, thickness, and age of the volcanic ash layers and the analysis of the structure and scale of the Mtkvari ignimbrite, the widely distributed ash likely resulted from a Plinian-type eruption in the Samtskhe-Javakheti volcanic highland. These eruptions led to the formation of the large-scale caldera structure (Niala caldera) and the Mtkvari ignimbrite. The inferred caldera extends to the northeastern territory of Türkiye (Turkey), i.e., NE of the Kars Plateau. Ideally, this western portion of the caldera and volcanic highlands can be characterized in the future, and a unified structure model of this volcanic center can be established.
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Acknowledgements
The authors would like to thank to Dr. Maya Bugsianidze for sharing some volcanic ash samples. The authors are very grateful to Prof. Karoly Nemeth whose thoughtful comments and constructive suggestions helped to improve the earlier version of the manuscript.
Funding
This research was made possible within the frames of an international joint project entitled “A cross-border study of petrogenesis, geodynamic setting, and gold mineralization potential of the Late Cenozoic magmatism on the Erzurum-Kars (Turkey) and Samtskhe-Javakheti (Georgia) Plateaus” funded by the Scientific and Technological Research Council of Türkiye (TUBİTAK) (Project # 118Y272) and the Shota Rustaveli National Sciences foundation of Georgia (SRNSF) (Project 04/02).
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Okrostsvaridze, A., Gamkrelidze, I., Lee, YH. et al. U–Pb geochronology and geochemistry of volcanic ash layers in the Eastern Caucasus intermountain Neogene basin: implications for their sources. Arab J Geosci 17, 129 (2024). https://doi.org/10.1007/s12517-024-11914-7
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DOI: https://doi.org/10.1007/s12517-024-11914-7