Browsing by Author "Keskin, M."

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Determination of Bioactivity and Antimicrobial Activity of Bumblebee (Bombus Terrestris L.) Brood Cover Wax Material
(Hellenic veterinary Medical Soc, 2022) Erkan, C.; Kara, Y.; Keskin, M.; Ertrk, O.; Goesterit, A.; Kolayli, S.
Bumblebee (Bombus terrestris L.) is a bee species that take part in pollination. Although Bumblebee (Bombus terrestris L.) is thought to be used only in pollination but, it is not only take part in pollination. It could be used to produce different products. Brood cover wax material is a kind of bumblebee product that produced by Bumblebee (Bombus terrestris L.) in order to cover their nest. Although it is considered to be waste for human health, brood cover wax material is an important hive product with its antioxidant and antimicrobial activities. In this study, Bumblebee brood cover wax material was produced under laboratory conditions in a controlled manner. Biochemical characterization of brood cover wax material obtained from five different colonies was performed and antimicrobial ac-tivities were determined. Accordingly, it was determined that the total phenolic content of the samples ranged between 3.778 +/- 0.165 and 9.504 +/- 0.353 mg GAE/g. In addition, it was observed that the samples were rich in p-coumaric acid, luteolin, quercetin, t-sinnamic acid, chrysin and pinocembrin components. Obtained results showed that brood cover wax material, which also possessed antimicrobial activity, had nearly equivalent activity to Apis mellifera L. beehive products such as honey, pollen and bee bread. The data obtained could be concluded that brood cover wax material could be used an alternative product for human health applications.
The Geochronology and Origin of Mantle Sources for Late Cenozoic Intraplate Volcanism in the Frontal Part of the Arabian Plate in the Karacadag Neovolcanic Area of Turkey. Part 1. The Results of Isotope-Geochronological Studies
(Pleiades Publishing inc, 2012) Keskin, M.; Chugaev, A. V.; Lebedev, V. A.; Sharkov, E. V.; Oyan, V.; Kavak, O.
This paper considers results from isotope-geochronological (K-Ar) studies of the products of Neogene-Quaternary volcanism in the Karacadag area, which is situated within the northern frontal part of the Arabian plate. It was found that magmatic activity has been evolving at this location for at least the last 11-10 Myr and was distinctly discrete in character. Three stages of volcanism have been identified: (I) Early or Miocene, similar to 11-6.7 Ma; (II) Middle or Pliocene-Early Quaternary, 4-1 Ma; and (III) Late or Late Quaternary, 0.4-0.1 Ma. The most recent manifestations of magmatic activity in the region date back to about 100000 years ago. An analysis of the spatial distribution of volcanic centers of different ages in the Karacadag neovolcanic area shows that the magmatism of that region involved a lateral migration of activity from northwest to southeast along a major regional tectonic fault. The migration was caused by the movement of local tension zones where the lithosphere was thinner and deep-seated mantle magmas were ascending.
The Geochronology and Origin of Mantle Sources for Late Cenozoic Intraplate Volcanism in the Frontal Part of the Arabian Plate in the Karacadag Neovolcanic Area of Turkey. Part 2. The Results of Geochemical and Isotope (sr-Nd Studies
(Pleiades Publishing inc, 2012) Keskin, M.; Chugaev, A. V.; Lebedev, V. A.; Sharkov, E. V.; Oyan, V.; Kavak, O.
A geochemical and isotope-geochemical (Sr-Nd-Pb) study has been carried out for the Karacadag neovolcanic area, which is situated within the frontal part of the Arabian plate. The obtained data and the results of petrological modeling show that the petrogenesis of parental magmas in the Karacadag neovolcanic area involved two compositionally different mantle sources; one consisted of garnet-bearing peridotites of the asthenosphere mantle and the other was spinel-bearing peridotites of the enriched subcontinental lithosphere mantle. During early stages in the evolution of the magmatic system, deep-seated asthenospheric magmas were ascending to the surface while intensively interacting with the melts that had been generated at upper mantle depths. The interaction gradually diminished, so that the later effusive rocks mostly have compositions that are similar to those of the primitive asthenospheric magmas. It is shown that a significant (up to 17-18 wt % of the mantle melt) assimilation of crustal material could take place only during the initial phases of the magmatism. Periodic replenishment of the magma chambers by primitive magmas, which resulted in an observable high degree of homogeneity in the composition of young effusive rocks, was also of importance in the petrogenesis of lavas during the evolution of volcanic activity.
Geochronology of Late Cenozoic Volcanism in the Area of Lake Van, Turkey: an Example of Developmental Dynamics for Magmatic Processes (Vol 433, Pg 1031, 2010)
(Maik Nauka/interperiodica/springer, 2010) Lebedev, V. A.; Sharkov, E. V.; Keskin, M.; Oyan, V.
An isotope-geochronological study has been performed to examine the products of Late Cenozoic collision volcanism on the northern coast of Lake Van, Turkey. We obtained 45 new K-Ar dates, based on which the principal time characteristics of volcanic activity in the region have been determined. Volcanic activity in the northern coast of Lake Van has lasted similar to 15 myr; it has had an expressed discrete nature, when periods of intense volcanic activity alternated with long-lasting pose periods. Four stages of Neogene-Quaternary volcanism have been identified: Middle Miocene (15.0-13.5 Ma), Late Miocene (10-9 Ma), Pliocene (5.8-3.7 Ma), and Quaternary (1.0-0.4 Ma). The average duration of the stages was 1-2 myr; the stages were separated from each other with periods of inactivity of approximately equal lengths (similar to 3 myr). For each of the Pliocene and Quaternary stages, three additional phases of volcanism have been identified, which were separated from each other with short time intervals (a few hundred thousand years). The last burst of volcanic activity in the study area occurred similar to 400 ka; similar to Quaternary volcanism in general, it was not characterized by a high intensity. An important result of the studies performed was to confirm the existence of a separate Middle Miocene stage of collision volcanism for the Caucasian-Anatolian Segment of the Alpine Fold Belt. New geochronological data generated presented in this paper indicate that Neogene-Quaternary volcanism in this portion of the belt started much earlier (similar to 15 Ma) than assumed by the majority of the previous researchers.
Geochronology of Late Cenozoic Volcanism in the Area of Van Lake, Turkey: an Example of Development Dynamics for Magmatic Processes
(2010) Lebedev, V.A.; Sharkov, E.V.; Keskin, M.; Oyan, V.
An isotope-geochronological study has been performed to examine the products of Late Cenozoic collision volcanism on the northern coast of Van Lake, Turkey. We obtained 45 new K-Ar dates, based on which the principal time characteristics of volcanic activity in the region have been determined. The total duration of magmatic activity in the area of the northern coast of Van Lake has lasted 15 myr; it has had an expressed discrete nature, when periods of intense volcanic activity alternated with lasting breaks in eruptions. Four stages of Neogene-Quaternary volcanism have been identified: Middle Miocene (15.0-13.5 myr), Late Miocene (10-9 myr), Pliocene (5.8-3.7 myr), and Quaternary (1.0-0.4 Ma). The average duration of the stages has been 1-2 myr; the stages were separated from each other with periods of inactivity of approximately equal lengths (3 myr). For each of the Pliocene and Quaternary stages, three additional phases of volcanism have been identified, which were separated from each other with short time intervals (a few hundred thousand years). The last burst of volcanic activity in the area in question took place 400 ka; similar to Quaternary volcanism in general, it was not characterized by a high intensity. An important result of the studies performed was to confirm the existence of a separate Middle Miocene stage of collision volcanism for the Caucasian-Anatolian Segment of the Alpine Fold Belt. The data generated allow concluding that Neogene-Quaternary volcanism in this portion of the belt started much earlier (15 Ma) than assumed by the majority of the previous researchers. © 2010 Pleiades Publishing, Ltd.
Late Pleistocene Tendurek Volcano (Eastern Anatolia, Turkey). Ii. Geochemistry and Petrogenesis of the Rocks
(Pleiades Publishing inc, 2016) Lebedev, V. A.; Chugaev, A. V.; Unal, E.; Sharkov, E. V.; Keskin, M.
The series of two papers presents a comprehensive isotope-geochronological and petrologicalgeochemical study of the Late Quaternary Tendurek Volcano (Eastern Turkey), one of the greatest volcanoes within the Caucasian-Eastern Anatolian segment of the Alpine foldbelt. The second article discusses the results of petrogenetic modeling, role of AFC-processes in the petrogenesis of magmas and the nature of mantle source of the Tendurek Volcano. Based on geochronological data, geochemical and isotopegeochemical (Sr-Nd-Pb) characteristics of the studied rocks we suggest the petrological model which well describe the evolution of magmatic system of the Tendurek Volcano during the whole period of its activity. The data obtained indicate that the igneous rocks of the Tendurek Volcano belong to the same homodromous volcanic series (trachybasalt-tephrite-phonotephrite-tephriphonolite-trachyandesite-trachyte-phonolite), which are dominated by the intermediate and moderately-acid varieties of the eruption products. The leading role in the petrogenesis of the lavas was played by the fractional crystallization processes, which, according to isotope-geochemical data, were sometimes complicated by the assimilation of upper crustal material. The mantle reservoir responsible for the magmatic activity within the major part of the Eastern Anatolia in the Late Quaternary time was represented by the OIB-type mantle. It was subject to slight metasomatic changes as a result of earlier deepening and remelting of the Arabian Plate slab, which was subducted under the region through the end of the Miocene. The depth of the magma-generating source is estimated at around 80 km, which corresponds to the upper part of the asthenospheric wedge under the region, based on geophysical data.
Late Pleistocene Tendurek Volcano (Eastern Anatolia, Turkey): I. Geochronology and Petrographic Characteristics of Igneous Rocks
(Maik Nauka/interperiodica/springer, 2016) Lebedev, V. A.; Sharkov, E. V.; Unal, E.; Keskin, M.
The series of two papers presents a comprehensive isotope-geochronological and petrological-geochemical study of the Late Quaternary Tendurek Volcano (Eastern Turkey), one of the greatest volcanoes within the Caucasian-Eastern Anatolian segment of the Alpine foldbelt. The first article discusses the results of chronostratigraphic reconstruction and provides the main petrographic characteristics of the Tendurek's igneous rocks. The K-Ar dating results show that the magmatic activity of the Tendurek Volcano developed in the Late Pleistocene time, over the period of the last 250 thousand years. Five discrete phases (I-250-200 ka, II-200-150 ka, III-150-100 ka, IV-100-70 ka, and V-< 50 ka) of the youngest magmatism were identified in this study. The first two phases were represented by the fissure eruptions of alkaline basic lavas and subsequent formation of vast lava plateaus, the CaldA +/- ran and DogubeyazA +/- t plains. In the following phases, the intermediate and moderately-acid volcanic rocks of mildly-alkaline or alkaline series started to dominate among the eruption products. According to their petrographic characteristics, the rocks of Tendurek Volcano are assigned to the alkaline association with Na-specifics (hawaiites-mugearites-benmoreites). The available geological, isotope-geochronological, and geomorphological data suggest that the Tendurek Volcano is potentially active. Nowadays, Tendurek reaches the caldera stage of its development.