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Öğe Geology and mineralogy of Late Miocene clayey sediments in the southeastern part of the Central Anatolian Volcanic Province, Turkey(CLAY MINERALS SOC, 2008) Guerel, Ali; Kadir, SelahattinLate Miocene clayey sediments were deposited in lake-margin and shallow-lake environments of the southeastern Central Anatolian Volcanic Province (CAVP). Yellow to red mudstone, alternating with thin beds of conglomerate and sandstone in the Mustafapasa Formation, is overlain by altered white Cemilkoy ignimbrite. Grain size fines upward in each sequence (conglomerate, sandstone, and mudstone). The occurrence of reddish coloration upward, ripple marks, desiccation cracks, plant rootlets and remnants, and the development of initial-stage paleosols in association with smectite reveal that the area underwent alternating periods of siliciclastic and volcaniclastic sediment Supply (wet) and drying, Micromorphologically, the development of spongy smectite in mudstone of the Mustafapasa Formation and vermiform kaolinite in the Cemilkoy ignimbrite on resorbed detrital feldspar and devitrified glass reveals in situ precipitation driven by dissolution and precipitation mechanisms. In addition, alteration of these sediments may have resulted in the depletion of soluble alkaline elements, such as Ca, Na, and K, from the ignimbrite downward into the Mustafapasa Formation. Alternatively, the leaching of these elements - due to the hydrologically open system of the lake environment - may have resulted in the enhancement of Al+Fe/Si-favored precipitation of kaolinite in an acidic environmental condition, namely, of the altered Cemilkoy ignimbrite at the top of the profile of the Mustafapasa Formation, and of smectite in an alkaline setting within lower-level sediments where carbonate minerals were lacking. The coexistence of smectite with accessory illite indicates that illitization occurred via release of K and Al during excess desorption of feldspar. Large Ni and Co values in mudstone samples, and Fe oxidized and partly chloritized pyroxene and hornblende, indicate that the basin was also affected by ophiolite-related supply.Öğe Geology of Late Miocene clayey sediments and distribution of palaeosol clay minerals in the north-eastern part of the Cappadocian Volcanic Province (Arapli-Erdemli), central Anatolia, Turkey(SCIENTIFIC TECHNICAL RESEARCH COUNCIL TURKEY-TUBITAK, 2013) Kadir, Selahattin; Gurel, Ali; Senem, Hulya; Kulah, TacitThe study area is situated in the Arapli-Erdemli (Kayseri) area in the north-eastern part of the Cappadocian Volcanic Province (CVP), central Anatolia. The Late Miocene series comprises lacustrine and fluvial deposits interbedded with ignimbrites and lava flows. The Late Miocene Mustafapasa member of the Urgup Formation comprises yellow to red mudstone that alternates with thin sandstone beds in the north-eastern part of the CVP. This unit continues upward through the Cemilkoy ignimbrite palaeosol layers (comprising altered Cemilkoy ignimbrite, vertisol and well-developed palaeosol layers), the Gordeles ignimbrite and red palaeosol layers, and includes two fallout levels; it is overlain by the Kizilkaya ignimbrite. The Mustafapasa member is dominated by smectite +/- illite +/- chlorite, whereas the altered Cemilkoy ignimbrite is predominantly kaolinite +/- smectite +/- chlorite. The underlying lower level of the Gordeles ignimbrite contains palaeosol layers, and continues upward through smectite-dominated layers. Alteration of feldspars and glass shards in the Cemilkoy and Gordeles ignimbrites resulted in the depletion of soluble alkaline elements (such as Ca, Na and K) from these ignimbrites downward to the Mustafapasa member, and palaeosol levels (Bayramhacili member) in the Arapli area favoured precipitation of smectite in an alkaline environment. However, the absence of these elements in these ignimbrites may have resulted in the enhancement of Al+Fe/Si-favoured precipitation of kaolinite in an acidic environment. Conversely, palaeosol of the Erdemli area consists of smectite +/- illite +/- chlorite. Micromorphologically, flaky smectite rims illite in both the Arapli and Erdemli areas and this can be explained by the release of K and Al during desorption of feldspar. Additionally, higher Ni, Co and Cr2O3 values in the mudstone samples of the Mustafapasa member and palaeosol levels, the presence of iron oxide and partially chloritised pyroxene and hornblende, together with ophiolitic and metamorphic grains, indicate that the basin also accumulated ophiolitic and metamorphic rock fragments in its sediment supply. This suggests that the Arapli area in the southern part of the CVP has undergone erosion, and that the present-day Erdemli area was close to the shallow-lake depositional environment of the northern part of CVP.Öğe Geology, mineralogy and origin of clay minerals of the Pliocene fluvial-lacustrine deposits in the Cappadocian volcanic province, central Anatolia, Turkey(CLAY MINERALS SOC, 2006) Gurel, Ali; Kadir, SelahattinThe Guzeloz-Incesu Plateaus are situated in the central and eastern parts of the Cappadocian volcanic province (central Anatolia). This province contains many ignimbrite levels, andesite, basalt intercalated with several paleosols, calcrete, carbonate, fluvial sediments, diatomaceous clayey sediments and pyroclastic sedimentary levels. The presence of mottling, sesquioxide, root traces, rhizoids and burrows in continuous, finely bedded and laminated sediments, paleosols, calcrete, the occurrence of bone- and teeth-bearing reworked pyroclastic materials, and the description of the lithofacies in the study area indicate fluvial and shallow-lake environments. These environments are dominated by smectite and illite, with traces of kaolinite, associated mainly with plagioclase, K-feldspar, quartz, calcite, opal-CT, pyroxene (diopside, rare hypersthene), and locally trace amounts of gypsum and sepiolite. Smectite predominates in paleosols and calcrete units, and generally increases upwards in the profiles, coinciding with a gradual increase in the degree of alteration. Partial to complete alteration of plagioclase, K-feldspar, pyroxene and partial devitrification of glass-shard particles in pyroclastic rocks, development of microsparitic to sparitic cement comprising euhedral rhombic calcite crystals between irregular clay nodules in paleosol and calcrete samples, along with the occurrence of dogtooth-type sparitic crystals in fractures, desiccation cracks and geopetal-type fenestrae, indicate alternating periods of drought and wet, resulting in the development of paleosols and calcretes. Micromorphological development of spongiform smectite on mainly relict feldspar and, locally, on glass shards, indicates an authigenic origin, whereas illite formed either authigenically or by conversion of smectite to illite-smectite.Öğe Geology, mineralogy, geochemistry, and depositional environment of a Late Miocene/Pliocene fluviolacustrine succession, Cappadocian Volcanic Province, central Anatolia, Turkey(SCIENTIFIC TECHNICAL RESEARCH COUNCIL TURKEY-TUBITAK, 2014) Goz, Ersel; Kadir, Selahattin; Gurel, Ali; Eren, MuhsinThis paper investigates the mineralogy, geochemistry, and depositional environment of Late Miocene/Pliocene fluviolacustrine deposits, including multiple ignimbrite levels and andesitic and basaltic lavas, within the Cappadocian Volcanic Province (CVP) of central Anatolia, Turkey. Palaeosols and calcretes formed within these terrestrial sedimentary rocks under near-surface or surface conditions. The palaeosols are composed predominantly of smectite +/- illite with feldspar, quartz, calcite, opal-CT, and amphibole, and the calcretes mainly of calcite with minor feldspar, quartz, and accessory smectite +/- palygorskite. The palygorskite occurs on and between the calcite crystals in the calcretes and at the edges of smectite flakes within the palaeosols, indicating an in situ formation from evaporated alkaline water rich in Si and Mg and poor in Al under arid or seasonally arid climatic conditions. In the palaeosols and calcretes, negative Ba, Nb, Ce, Sr, and Ti anomalies and an enrichment of light rare earth elements relative to medium rare earth elements and heavy rare earth elements, with a distinct negative Eu anomaly, likely reflect the alteration of feldspars and amphiboles in the ignimbrite. The alteration of the ignimbrites caused the depletion of SiO2, Al2O3+Fe2O3, TiO2, and K2O through the precipitation of smectite +/- illite in the palaeosols and CaO in the form of calcite in the calcretes. The delta O-18 values of the calcretes and limestones range from -8.71% to -10.71%, which are mainly related to the involvement of high-elevation meteoric water, whereas the delta C-13 values for the same rocks vary between -1.97% and 5.71%. The positive delta C-13 values for the limestones reflect calcite precipitation in isotopic equilibrium with meteoric water in a lake. The slightly negative delta C-13 values of the lacustrine limestone carbonates may indicate precipitation from a relatively thick water column and an inflow of surface or groundwater through the ignimbrites with high Ba/Sr values. Conversely, the calcrete delta C-13 values (3.0% to 4.97%) may suggest a pedogenic origin with low plant respiration rates and a predominance of C-4 plants. Based on stable oxygen isotope values from the lake sediments and calcretes, this study suggests that the global warming trend that followed the Late Miocene continued into the Pliocene within the CVP.Öğe Late Quaternary climate and sea-level changes recorded in sediment composition off the Buyuk Menderes River delta (eastern Aegean Sea, Turkey)(PERGAMON-ELSEVIER SCIENCE LTD, 2007) Ergin, Mustafa; Kadir, Selahattin; Keskin, Seref; Turhan-Akyuz, Nilufer; Yasar, DoganInfluences of Holocene climatic and sea level changes on sedimentation on the continental shelf off the Buyuk Menderes River delta, SW Turkey were investigated using grain size and X-ray clay mineralogical data on surficial and 14C-dated core sediments collected at 19-81 m water depths. Modern, fine-grained, siliciclastic sediments cover most of the seafloor of inner to mid-shelf areas. A narrow, relict belt extends from northwest to south (at 66-81 m water depths), where sediments are characterized by abundant sand and gravel (27-52%) and biogenic carbonate (16-44%) contents, and microscopic examination suggests an older origin. The radiocarbon ages of mid and lower sections in cores (3670-10,380 yr BP) reflect sedimentation under depositional conditions from early to late Holocene in the study area. Additionally, downcore changes of grain size toward coarser-grained sediments most probably record global climatic effects with sea level changes, specifically the transition from lowstand in early Holocene to highstand at mid-late Holocene. The presence of this relict belt in offshore waters can be attributed largely to active uplift tectonics. The coarser-grained relict belt, compared with available seismic profiles, corresponds to an lowstand unconformity of bottomset beds of the prograding Buyuk Menderes Delta. Reconstruction from nautical charts clearly showed the presence of an E-W-trending submarine canyon ("Paleo-Buyuk Menderes River valley") in the course of Buyuk Menderes Graben. This is interpreted as product of combination of sea-level lowstands and subsidence tectonics throughout the late Quaternary. Smectite (35-62 %), illite (28-51 %) and kaolinite (12-19 %) constitute the dominant clay minerals in the < 2 mu m fraction of the surface sediments. The patterns of clay mineral distribution suggest sediment transport from the Buyuk Menderes River and dispersal from the river to the outer continental shelf by the prevailing current regime. Downcore changes in the clay mineral assemblages (downward-decreasing smectite/iilite ratios) reflect changes in weathering conditions of the terrigenous source, from a colder climate during early Holocene to relatively warmer periods toward the present. Widely occurring partly metamorphosed volcanic rocks characterize the major geological sources of clay minerals on the adjacent hinterland. (c) 2007 Elsevier Ltd and INQUA. All rights reserved.Öğe MINERALOGICAL AND GEOCHEMICAL CHARACTERISTICS AND GENESIS OF THE GUZELYURT ALUNITE-BEARING KAOLINITE DEPOSIT WITHIN THE LATE MIOCENE GORDELES IGNIMBRITE, CENTRAL ANATOLIA, TURKEY(CLAY MINERALS SOC, 2014) Kadir, Selahattin; Kulah, Tacit; Eren, Muhsin; Onalgil, Nergis; Gurel, AliThe Guzelyurt kaolinite deposit is an important source of raw material for the ceramics industry in Turkey. No detailed mineralogical or geochemical characterizations of this deposit have been undertaken previously and these were the goals of the present study. The Guzelyurt alunite-bearing kaolinite occurs along a fault zone in the Late Miocene Gordeles ignimbrite, which consists of dacitic and andesitic tuffs. Horizontal and vertical mineralogical zonations. with gradual transitions were observed within the alteration zone. The inner kaolinite, alunite, and 7 angstrom halloysite zones progress horizontally outward to a smectite zone; and native sulfur- and cinnabar-bearing alunite with 7 angstrom halloysite and porous silica zones increase as one progresses up through the profile. Fe-(oxyhydr)oxide phases associated with native sulfur and cinnabar demonstrate that multiple hydrothermal-alteration processes resulted in kaolinization and alunitization of the deposit. The kaolinization of feldspar, Fe-(oxyhydr)oxidation of hornblende and mica, the presence of kaolinite as stacked and, locally, book-like forms, and of 7 angstrom halloysite tubes, and smectite flakes as a blanket on altered volcanic relicts indicate an authigenic origin for this deposit. The leaching of Si + Mg + K and Ba + Rb, the retention of Sr, the enrichment of light rare earth elements relative to the heavy rare earth elements, and the negative Eu anomalies suggest that fractionation of plagioclase and hornblende occurred within the volcanics. The oxygen- and hydrogen-isotopic values of the kaolinite, 7 angstrom halloysite, smectite, and smectite + kaolinite fractions reflect a steam-heated environment at temperatures in excess of 100 degrees C. An increase in the delta O-18 and 5180 values of 7 angstrom halloysite relative to kaolinite suggests its formation under steam-heated magmatic water, the mixing of steam and meteoric water near the surface, and evaporation. The oxygen- and sulfur-isotopic compositions of alunite suggest the direct influence of steam-derived sulfur. The Guzelyurt alunite-bearing kaolinite deposit is inferred to have formed after an increase in the (Al +/- Fe)/Si ratio and the leaching of alkali elements, which are driven by the sulfur-bearing low-temperature hydrothermal alteration of feldspar, hornblende, and volcanic glass under acidic conditions within the Neogene dacitic and andesitic tuffs.Öğe Mineralogy, geochemistry and genesis of the modern sediments of Seyfe Lake, Kirsehir, central Anatolia, Turkey(PERGAMON-ELSEVIER SCIENCE LTD, 2015) Onalgil, Nergis; Kadir, Selahattin; Kulah, Tacit; Eren, Muhsin; Gurel, AliSeyfe Lake (Kirsehir, Turkey) is located within a depression zone extending along a NW-SE-trending fault in central Anatolia. Evaporite and carbonate sediments occur at the bottom of the lake which is fed by high-sulfate spring and well waters circulating N-S through salt domes. The recent sediments of Seyfe Lake are deposited in delta, backshore, beach, mud-flat and shallow lake environments. In the mud-flat environment, calcite, gypsum, halite, and thenardite are associated with fine-grained detrital sediments. Sediments from the margin to the lake center are distributed as calcite, gypsum and halite thenardite, yielding an annular distribution pattern. An increase in Na2O, SO3, and S, and a decrease in CaO toward the lake center are due to sediment distribution. On the other hand, a positive correlation of SiO2 with MgO, K2O, Na2O, Al2O3, and Fe2O3 + TiO2 is attributed to the presence of smectite, illite and feldspar. In addition, a positive correlation of Sr and Ba with CaO is related to the amount of gypsum in the sediments. Strontium is associated with in situ gypsum crystals; it increases in the intermediate and central zones of the lake as a result of a relative increase in salinity toward the lake center. The association of Sr with gypsum in the sediments suggests that Ca and Sr were derived from Sr-bearing evaporites and their carbonate host rocks, which were the likely aquifers for the brine. The S- and O-isotopic compositions of sulfate crystals range from +19.1 parts per thousand to +21.7 parts per thousand and from +16.9 parts per thousand to +20.9 parts per thousand SMOW, respectively, suggesting precipitation in a closed lake system. A relative increase of oxygen and sulfur isotope ratios toward the lake center suggests dissolution of gypsum in the host rock, with contributions from circulating groundwater and sulfate reduction (possibly by bacterial reduction). Sr-87/Sr-86 isotope ratios range from 0.707286 to 0.707879, suggesting a non-marine Oligo-Pliocene evaporitic host rock source for precipitation in Seyfe Lake. The concentration of Sr- and S-isotope ratios in the gypsum crystals indicates formation by precipitation/recrystallization from brine rather than from seawater. (C) 2014 Elsevier Ltd. All rights reserved.Öğe MINERALOGY, GEOCHEMISTRY, AND GENESIS OF MUDSTONES IN THE UPPER MIOCENE MUSTAFAPASA MEMBER OF THE URGUP FORMATION IN THE CAPPADOCIA REGION, CENTRAL ANATOLIA, TURKEY(CLAY MINERALS SOC, 2014) Kulah, Tacit; Kadir, Selahattin; Gurel, Ali; Eren, Muhsin; Onalgil, NergisThe Upper Miocene Mustafapasa member of the Urgup Formation in the Cappadocia region consists predominantly of mudstones, sandstone, and conglomerate lenses with ignimbrite and basalt intercalations. The mudstones are an important source of raw materials for the ceramics industry in Turkey. A detailed mineralogical, geochemical, and genesis study of these materials has not been performed previously and the present study aims to fill that gap. The characteristics of mudstones of the Mustafapasa member were examined using X-ray diffraction, scanning and transmission electron microscopy, energy dispersive spectroscopy, and chemical analyses. Weathering products of ophiolitic and pyroclastic rocks were transported into the tectonically subsided zone where they accumulated as fluvial and lacustrine deposits. Weathering in the mudstones is evidenced by smectite flakes associated with relict pyroxene, rodlike amphibole, feldspar, and volcanic glass. The chemical composition of mudstones and their distribution suggest that the depositional basin was supplied with ophiolitic material in the south and ignimbrite material in the north. This interpretation is based on an increase in the quantity of feldspar and opal-A and a decrease in the Fe2O3+MgO/Al2O3+SiO2 ratio from south to north in the study area. The northward increases in Light Rare Earth Elements/Heavy Rare Earth Elements, La/Yb, Zr/Ni and Zr/Co ratios and Nb, Ba, Rb, Sr, and Eu in the mudstones of the Mustafapasa member with positive Eu anomalies suggest that the Fe, Mg, Al, and Si required to form smectite were supplied mainly through the decomposition of amphiboles, pyroxenes, feldspars, and volcanic glass during weathering processes. After the deposition of mudstones, relative increases in evaporation-controlled Ca, K, and Al in pore water favored the partial dissolution of Ca-bearing minerals and smectite flakes and in situ precipitation of calcite and traces of illite fibers under alkaline micro-environmental conditions during early diagenesis.
