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Collision-related Quaternary mafic volcanism to the north of Lake Van (Eastern Anatolia, Turkey) occurred by eruptions from both volcanic centres and extensional fissures trending approximately north-south. We report new major, trace and rare earth element abundances, Sr-Nd-Pb isotope ratios and K-Ar ages for basaltic and more evolved hawaiitic and mugearitic lava flows. The new K-Ar ages indicate that magmatic activity occurred between 10 and 04 Ma. The volcanic products consist of mildly alkaline lavas, ranging in composition from basalt to hawaiite and mugearite. Energy-constrained assimilation and fractional crystallization (EC-AFC) model calculations suggest that the least evolved basaltic samples were unaffected by the combined effects of fractional crystallization and crustal contamination processes, in contrast to the more evolved hawaiitic and mugearitic lavas, which have experienced up to 2-3% crustal assimilation. Calculations based on crustal temperatures and Curie point depths indicate that the magma chamber, from which the basic to evolved lavas were derived, might be located at a depth of around 6-8 km, within the upper crust. Enrichment of large ion lithophile elements and light rare earth elements relative to high strength field elements, and higher 87Sr/86Sr and Pb isotopic ratios and lower 144Nd/143Nd of the least evolved basaltic samples indicate that the mantle source region of the Quaternary mafic magmas might have been enriched by melts that were derived from subducted sediments with a partial melting degree of around 10% rather than from Altered Oceanic Crust melts and fluids. Our model melting calculations show that the basaltic melts might have been produced by melting of a mantle source containing both amphibole and garnet with a partial melting degree of 3%. Results of our petrological models indicate that a metasomatized mantle source, which was infiltrated by a mixture of 93% mantle melt and 7% sediment melt plus 001% residual rutile, added to mantle melt, could have been the source composition of the basaltic melts that produced the Quaternary mafic volcanism. [ABSTRACT FROM AUTHOR]

Abstract The Quaternary (0.66–0.63 Ma) nepheline basanites (ne - basanite) are the firstly observed volcanic products of Arabia-Eurasia collision on Bitlis Pötürge Massif. They composed of clinopyroxene, olivine, Ti-magnetite, Cr spinel, and nepheline. The forsterite compositions of olivines range between 73 and 83%, calcic clinopyroxenes show modest variations in Wo 48–57 -En 37–45 -Fs 5–7 and nephelines occur as minor minerals within the networks of other groundmass minerals. They are characterized by low SiO 2 (40.16–41.96 wt%), high MgO contents (8.54–9.73 wt%) and similar Sr Nd isotopic compositions with Arabian Plate volcanics. Mineral and whole rock thermobarometry yield crystallization pressure and a temperature range between 8 and 20 kbar and 1301 °C – 1035 °C respectively. Lavas have high Mg-number (>0.58), high Cr and Ni contents and strong LREE enrichment but depletion in Rb, K, and Pb. Trace elements together with Sr isotopic compositions inferred negligible assimilation of the local upper crustal material. The calculated average pressure and temperature of mantle melting for ne- basanites is 2,85 kbar and 1353 °C respectively. FC3MS (wt% FeO/CaO-3*MgO/SiO 2) parameter and melting models using REE data reveal Çatak basanites are products of amphibole and phlogopite bearing metasomatised lithospheric mantle in garnet stability field. They seem to originated from depths of ~ 85 km which corresponds to the base of the Arabian lithosphere in the region. Graphical abstract Unlabelled Image Highlights • The firstly observed collision related volcanics in Bitlis Suture Zone • The calculated average pressure and temperature of mantle melting is 2,85 kbar and 1353 °C. • They formed through the melts from Arabian Lithospheric mantle beneath the Bitlis Massif. [ABSTRACT FROM AUTHOR]

Ignimbrites are used extensively in masonry and decorative cladding not only in historical structures, but also in residential houses recently as well as monuments around Ahlat (Bitlis-Turkey) region because of their light weight, softness and insulating properties. The most famous architectural monument is the Ahlat Seljuk Tombs, in which ignimbrites were used for the structure. These are thousand year old gravestones that have been subjected to significant degradation over time caused by many physical and chemical effects. The aim of this study is revealing the mineralogical, petrographical, petrophysical and mechanical properties of fresh ignimbrites as well as determining the effect of lichens and capillarity on the deterioration of Seljuk gravestones in accordance with laboratory studies and field observations. A total of four different ignimbrite levels have been evaluated, which are widespread in the region and named as N1 (reddish brown), N2 (dark brown), N3 (yellowish gray) and N4 (black), respectively. Among these ignimbrites, the samples of N1 and N2 were employed in the construction of Seljuk gravestones. The lithic material content and welding degree are the main controlling factors of the engineering properties of ignimbrites. Laboratory test results indicate that high porosity of ignimbrites and transport of water mediated by capillarity accelerate the deterioration of ignimbrites. Furthermore, lichens play a preventive role in the deterioration mechanism of ignimbrites rather than disintegrating the tombstones. [ABSTRACT FROM AUTHOR]