Trace element geochemistry of Bitlis ignimbrites sourced by Quaternary Nemrut Volcano: inferences for A2-type magma generation in Eastern Anatolia post-collisional extensional setting

Year 2021, , 91 - 96, 20.12.2021

Hakan Çoban , Özcan Ali Kalkan

https://doi.org/10.17678/beuscitech.1021499

Abstract

In the study presented here, we investigated the K-Ar age determination and petrological significance of trace element compositions of Bitlis (Eastern Anatolia) ignimbrites associated with explosive activities of the well-known Nemrut volcano. K-Ar geochronological dating of Bitlis ignimbrite flow deposits gave the age of 790 ka which corresponds to the first products of pre-caldera stages of Nemrut stratovolcano. Bitlis trachydacitic ignimbrites with shoshonitic affinity are characterized by the typical negative anomalies of Eu, Nb-Ta, and Ti in chondrite-normalized spider and multi-element variation diagrams, and plot in the fields of within-plate and post-collisional tectonic setting in Rb vs Y+Nb discrimination diagram. Accordingly, similar to that of Nemrut volcanic products, trace element signatures (e.g., high Nb, Ce, Y, and Zr contents) of Bitlis ignimbrites show coincidence with geochemical characteristics of A2-type silicic magmas. Relative to the upper crust, higher La/Ba and Nb/La, and lower Ba/Ta and La/Ta ratios of Bitlis ignimbrites, which are close to that of Nemrut basalts, suggest an interaction between OIB-like basaltic magma and upper crust. Our results point to A2-type silicic magma generation in Eastern Anatolia post-collisional extensional setting, and Nemrut volcanic and pyroclastic rocks (e.g., Bitlis ignimbrites) formed by partial melting of upper crustal rocks at shallow level via interaction with OIB-like basaltic magma derived from a common mantle source.

Keywords

Bitlis ignimbrite, A2-type magma, K-Ar dating, Eastern Anatolia

Supporting Institution

Istanbul Technical University, Batman University

Project Number

special project

Thanks

We would like to thank Dr. Mustafa KUMRAL (ITU), who conducted geochemical analyses of rock samples at Istanbul Technical University. The corresponding author also thanks Dr. Sema TETİKER, who contributed to K-Ar isotopic analysis.

References

• Çubukçu, H.E., Ulusoy, I., Aydar, E., Ersoy, O., Şen, E., Gourgaud, A., and Guillou, H., 2012. Mt. Nemrut volcano (Eastern Turkey): temporal petrological evolution. J Volcanol Geotherm Res 209–210:33–60.
• Eby, G.N., 2011. A-type granites: magma sources and their contribution to the growth of the continental crust. Seventh Hutton Symposium on Granites and Related Rocks, pp. 50–51.
• Karaoğlu, Ö., Özdemir, Y., Tolluoğlu, A.Ü., Karabıyıkoğlu, M., Köse, O., and Froger, J.-L., 2005.Stratigraphy of the volcanic products around Nemrut Caldera: implications for reconstruction of the caldera formation. Turkish Journal of Earth Sciences 14, 123–143.
• Kay, S.M., and Copeland, P., 2006. Early to middle Miocene back-arc magmas of the Neu-quén Basin: geochemical consequences of slab shallowing and the westward drift of South America. Geological Society of America Special Paper 407, 185–213.
• Koralay, T., Özkul, M., Kumsar, H., Çelik, S.B. ve Pektaş, K., 2014. Tarihi Yapılarda Mineralojik, Petrografk ve Jeoteknik Çalışmaların Önemi: Bitlis Kalesi Örneği (Bitlis-Doğu Anadolu), Selçuk Üniv. Müh.-Mim. Fak. Dergisi, Sayı, 2-3, s.54-68.
• Le Maitre, R.W., Streckeisen, A., Zanettin, B., Le Bas, M.J., Bonin, B., Bateman, P.,Bellieni, G., Dudek, A., Efremova, S., Keller, J., Lameyre, J., Sabine, P.A., Schmid,R., Sorensen, H., and Woolley, A.R., 2002. Igneous Rocks: A Classification and Glossary of Terms. Recommendations of the International Union of Geological Sciences Subcommission on the Systematics of Igneous Rocks Cambridge University Press, p. 236.
• Notsu, K., Fujitoni, T., Ui, T., Matsuda, J., and Ercan, T., 1995. Geochemical features of collision-related volcanic rocks in central and eastern Anatolia, Turkey. Journal of volcanology and Geothermal Research 64, 171–192.
• Özdemir, Y., Karaoglu, Ö., Tolluoglu, A.U., and Gulec, N., 2006. Volcanostratigraphy and petrogenesis of the Nemrut stratovolcano, East Anatolian High Plateau): the most re-cent post-collisional volcanism in Turkey. Chemical Geology 226, 189–211.
• Pearce, J.A., 1996. Sources and settings of granitic rocks. Episodes 19, 120–125.
• Pearce, J.A., Bender, J.F., De Long, S.E., Kidd, W.S.F., Low, P.J., Güner, Y.,Şaroğlu, F., Yılmaz, Y., Moorbath, S., and Mitchell, J.G., 1990. Genesis of collision volcanism in eastern Anatolia, Turkey. Journal of Volcanology and Geothermal Research 44, 189–229.
• Rudnick, R.L., and Gao, S., 2004. Composition of the Continental Crust. In: Rudnick, R.L.(Ed.), Treatise on Geochemistry. Elsevier-Pergamon, Oxford, pp. 1–64.
• Saunders, A.D., Storey, M., Kent, R.W., and Norry, M.J., 1992. Consequences of plume-lithosphere interactions. In: B.C. STOREY, T. ALABASTER & R.J. PANKHURST, Eds., Magmatism and the causes of continental break-up. Geol. Soc. Spec. Publ., 68, 41-60.
• Schmincke, H-U., Sumita, M., and Paleovan scientific team., 2014. Impact of volcanism on the evolution of Lake Van (eastern Anatolia). III. Periodic (Nemrut) vs. episodic (Süphan) explosive eruptions and climate forcing reflected in a tephra gap between ca. 14 ka and ca. 30 ka. J Volcanol Geotherm Res 285:195–213.
• Sumita, M., and Schmincke, H-U., 2013. Impact of volcanism on the evolution of Lake Van I: evolution of explosive volcanism of Nemrut Volcano (eastern Anatolia) during the past >400,000 years. Bull Volcanol 75:1–32.
• Sun, S.S., and Mc Donough, W.F., 1989. Chemical and isotopic systematics of oceanic basalts: implications for mantle composition and processes. In: Saunders, A.D., Norry, M.J. (Eds.), Magmatism in Ocean Basins, Geological Society of London Spec. Publ., vol. 42, pp. 313–345.
• Koralay, T., Özkul, M., Kumsar, H., Çelik, S.B., and Pektaş,K.,2011.The effect of welding degree on geotechnical properties of an ignimbrite flow unit: the Bitlis castle case (eastern turkey). Environ. Earth Sci. 64, 869–881.
• Whalen, J.B., Currie, K.L., and Chappell, B.W., 1987. A-type granites geochemical characteristics, discrimination, and petrogenesis. Contributions to Mineralogy and Petrology95, 407–419.
• Yılmaz, Y., Güner, Y.,and Şaroğlu, F., 1998. Geology of the quaternary volcanic centers of east Anatolia. Journal of Volcanology and Geothermal Research 85, 173–210.34M.