Ali Gürel

GEOLOGY, MINERALOGY AND ORIGIN OF CLAY MINERALS OF THE PLIOCENE FLUVIAL-LACUSTRINE DEPOSITS IN THE CAPPADOCIAN VOLCANIC PROVINCE, CENTRAL ANATOLIA, TURKEY

The Güzelöz-İncesu 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.

GEOLOGY AND MINERALOGY OF LATE MIOCENE CLAYEY SEDIMENTS IN THE SOUTHEASTERN PART OF THE CENTRAL ANATOLIAN VOLCANIC PROVINCE, TURKEY

Late 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 Mustafapaşa Formation, is overlain by altered white Cemilköy 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 Mustafapaşa Formation and vermiform kaolinite in the Cemilköy 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 Mustafapaşa 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 Cemilköy ignimbrite at the top of the profile of the Mustafapaşa 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.

Mixing processes in hydrothermal spring systems and implications for interpreting geochemical data: a case study in the Cappadocia region of Turkey

Mixing is a dominant hydrogeological process in the hydrothermal spring system in the Cappadocia region of Turkey. All springs emerge along faults, which have the potential to transmit waters rapidly from great depths. However, mixing with shallow meteoric waters within the flow system results in uncertainty in the interpretation of geochemical results. The chemical compositions of cold and warm springs and geothermal waters are varied, but overall there is a trend from Ca–HCO3 dominated to Na–Cl dominated. There is little difference in the seasonal ionic compositions of the hot springs, suggesting the waters are sourced from a well-mixed reservoir. Based on δ18O and δ2H concentrations, all waters are of meteoric origin with evidence of temperature equilibration with carbonate rocks and evaporation. Seasonal isotopic variability indicates that only a small proportion of late spring and summer precipitation forms recharge and that fresh meteoric waters move rapidly into the flow system and mix with thermal waters at depth. 3H and percent modern carbon (pmC) values reflect progressively longer groundwater pathways from cold to geothermal waters; however, mixing processes and the very high dissolved inorganic carbon (DIC) of the water samples preclude the use of either isotope to gain any insight on actual groundwater ages.RésuméLe mélange est un processus hydrogéologique dominant dans le système de sources thermales de la région du Cappadoce en Turquie. Toutes les sources émergent le long de failles, qui ont la capacité de transmettre des eaux rapidement depuis de grandes profondeurs. Toutefois, le mélange avec des eaux météoriques peu profondes à l’intérieur du système d’écoulement entraîne une incertitude dans l’interprétation des résultats géochimiques. Les compositions des eaux de sources chaudes et froides et des eaux géothermales sont variables, mais de façon générale il y a une tendance du pôle Ca–HCO3 vers le pôle Na–Cl. Il y a une différence saisonnière petite dans la composition ionique des sources chaudes, suggérant que les eaux sont issues d’un réservoir source où elles sont bien mélangées. Les concentrations δ18O et δ2H indiquent que toutes les eaux sont d’origine météorique mettant en évidence la température d’équilibre avec roches carbonatées et évaporation. Une variabilité isotopique saisonnière indique que seule une petite part de précipitations tardives de printemps et d’été constituent la recharge et que les eaux météoriques récentes s’écoulent rapidement dans le système et se mélangent avec les eaux thermales en profondeur. 3H et la concentration en carbone moderne (pmC) reflètent un cheminement souterrain de l’eau s’accroissant progressivement des eaux froides aux eaux géothermales; toutefois, les processus de mélange et la proportion élevée de carbone inorganique (DIC) des échantillon d’eau impliquent l’utilisation de l’un ou l’autre isotope pour obtenir quelque indication sur l’âge de l’eau souterraine récente.ResumenLa mezcla es un proceso hidrogeológico dominante en el sistema de manantiales hidrotermales en la región de Capadocia de Turquía. Todos los manantiales emergen a lo largo de fallas, las cuales tienen el potencial de transmitir aguas rápidamente desde grandes profundidades. Sin embargo, la mezcla con aguas meteóricas someras dentro de un sistema de flujo resulta en incertidumbres en la interpretación de los resultados geoquímicos. Las composiciones químicas de manantiales de aguas frías y cálidas y aguas geotermales son variados, pero sobretodo existe una tendencia desde el predominio de aguas Ca–HCO3 al predominio de las Na–Cl. Existe una pequeña diferencia en las composiciones iónicas estacionales de los manantiales calientes, lo cual sugiere que las aguas provienen desde un reservorio bien mezclado. Sobre la base de concentraciones de δ18O y δ2H, todas las aguas son de origen meteórico con evidencias de un equilibro de la temperatura con las rocas carbonáticas y la evaporación. La variabilidad isotópica estacional indica que solamente una pequeña proporción de las precipitaciones tardías de la primavera y del verano da lugar a la recarga y que las aguas meteóricas dulce se mueven rápidamente en el sistema de flujo y se mezclan con aguas termales en profundidad. Los valores 3H y el porcentaje de carbono moderno (pmC) reflejan progresivamente trayectorias más prolongadas desde aguas frías a geotermales, sin embargo, los procesos de mezcla y el muy alto carbono inorgánico disuelto (DIC) de las muestras de agua impiden el uso de cualquiera de los isótopos para conseguir un conocimiento más profundo sobre las edades reales del agua subterránea.摘要土耳其Cappadocia地区热水泉系统中,混合是一个主要的水文地质过程。所有的泉沿断层出现,这些断层有从深部快速输水的潜力。然而,水流系统内与浅层大气水混合可导致地球化学结果解译中的不确定性。冷泉和温泉化学组分及地热水的化学组分各种各样,但总的来说,有从Ca–HCO3主导到Na–Cl主导的趋势。热泉中季节性的离子组分差别很小,表明井水与热储水混合。根据δ18O 和 δ2H含量,所有的水来自大气,证据是其温度与碳酸盐岩和蒸发作用平衡。季节同位素变异性表明只有一小部分晚春和夏季降水形成补给,大气淡水迅速运移进入水流系统,并与深部的热水混合。3H及百分比现代碳(pmC)值反映出从冷到地热水的地下水通道逐渐变长。然而,混合过程和水样中非常高的溶解无机碳妨碍使用同位素获取实际的地下水年龄信息。ResumoO processo de mistura é o processo hidrogeológico dominante no sistema de nascentes hidrotermais na região da Capadócia, na Turquia. Todas as nascentes emergem ao longo de falhas, que têm o potencial de transmitir rapidamente águas de grandes profundidades. No entanto, a mistura com águas meteóricas de pequena profundidade dentro do sistema de fluxo resulta em incerteza na interpretação dos resultados geoquímicos. As composições químicas de nascentes frias e quentes e das águas geotérmicas são variadas, mas no geral há uma tendência para um domínio de Ca–HCO3 até um domínio Na–Cl. Há pouca diferença nas composições iónicas sazonais das nascentes termais, sugerindo que as águas são provenientes de um reservatório bem misturado. Com base nas concentrações de δ18O e δ2H, todas as águas são de origem meteórica, com evidência de equilíbrio da temperatura com rochas carbonatadas e evaporação. A variabilidade isotópica sazonal indica que apenas uma pequena porção da precipitação do final da primavera e do verão faz parte da recarga e que a água doce meteórica se move rapidamente para o sistema de fluxo e se mistura com águas termais em profundidade. Os valores de 3H e da percentagem de carbono moderno (pmC) refletem percursos de água subterrânea progressivamente mais longos das águas frias para as águas geotérmicas; no entanto, os processos de mistura e os valores muito elevados de carbono inorgânico dissolvido (DIC) nas águas subterrâneas impedem a utilização de qualquer isótopo para obter algum conhecimento sobre as idades atuais da água subterrânea.ÖzetKarışım, Türkiye’nin Kapadokya bölgesindeki sıcak su kaynak sisteminde baskın bir hidrojeolojik süreçtir. Tüm kaynak suları, çok derinlerden yüzeye doğru suyu hızlıca iletme potansiyeline sahip faylar boyunca çıkmaktadır. Ancak, akış sisteminde sığ meteorik sularla karışım jeokimyasal sonuçların yorumlanmasında belirsizliğe yol açmaktadır. Soğuk, sıcak ve jeotermal suların kimyasal bileşimleri farklı olmakla birlikte, bunlarda Ca–HCO3’den Na–Cl’ye doğru baskın bir iyon değişim eğilimi vardır. Sıcak su kaynaklarının mevsimsel iyonik bileşimlerindeki küçük değişim, suların önemli ölçüde karışım özellikli bir rezervuardan geldiğine işaret eder. δ18O ve δ2H konsantrasyonlarına göre, tüm sular, karbonat kayaçlar ve buharlaşma ile denge sıcaklığının kanıtı olup, meteorik kökenlidir. Mevsimsel izotopik değişim, bahar dönemi sonu ve yaz dönemi yağışından az miktarda beslenime ve genç meteorik suların akış sistemine hızlıca hareketine ve derinlerde sıcak sularla karışımına işaret eder. 3H ve pmC değerleri, soğuk sulardan jeotermal sulara doğru ilerleyen daha uzun yeraltısuyu akış yollarını yansıtmasına rağmen, karışım süreçleri ve çok yüksek çözünmüş inorganik karbon (DIC) içeren su örnekleri, izotopu kullanarak gerçek yeraltısuyu yaşları konusunda herhangi bir görüş sunulmasını engeller.

MINERALOGY, GEOCHEMISTRY, AND GENESIS OF MUDSTONES IN THE UPPER MIOCENE MUSTAFAPAŞA MEMBER OF THE ÜRGÜP FORMATION IN THE CAPPADOCIA REGION, CENTRAL ANATOLIA, TURKEY

The Upper Miocene Mustafapas-a member of the Ürgüp 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 Mustafapas-a 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, rod-like 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 Mustafapas-a 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.

MINERALOGICAL AND GEOCHEMICAL CHARACTERISTICS AND GENESIS OF THE GÜZELYURT ALUNITE-BEARING KAOLINITE DEPOSIT WITHIN THE LATE MIOCENE GÖRDELES IGNIMBRITE, CENTRAL ANATOLIA, TURKEY

The Güzelyurt 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 Güzelyurt alunite-bearing kaolinite occurs along a fault zone in the Late Miocene Gödeles 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 Å halloysite zones progress horizontally outward to a smectite zone; and native sulfur- and cinnabar-bearing alunite with 7 Å 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 Å 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 Å halloysite, smectite, and smectite + kaolinite fractions reflect a steam-heated environment at temperatures in excess of 100°C. An increase in the δD and δ18O values of 7 Å 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 Güzelyurt 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.

SEDIMENTOLOGICAL AND MINERALOGICAL INVESTIGATION OF THE LATE MIOCENE SUCCESSIONS OF AKTOPRAK BASIN (CENTRAL TURKEY): IMPLICATIONS FOR SEDIMENT SOURCE AND PALEOCLIMATES

Late Miocene (Messinian) alluvial and lacustrine deposits characterize the so-called Kızılbayır Formation of the Aktoprak Basin (central Turkey) and consist of conglomerate, sandstone, mudstone, limestone, marl, and dolomite units. These sediments are composed mainly of feldspar, quartz, hornblende, diopside, olivine, serpentine, calcite, and dolomite with subordinate palygorskite, chlorite, smectite, and illite. Studies by scanning electron microscopy indicate that calcite and dolomite show both meniscus and micrite-sparite-type cements, characteristic of both vadose and phreatic zones. Chlorite, smectite, and illite are products of the alteration of the underlying Güney Formation with subsequent transportation by local streams into the Kızılbayır Formation, and therefore these are considered to be reworked materials. Authigenic palygorskite and dolomite formed as a result of the calcretion of mudstone-carbonate units under alkaline conditions, with high Si, Ca, and Mg activity, and low Al, originated from ophiolitic and carbonate units based on the increase in Ni and Co. The paragenesis and textural features of the minerals of the alluvial fan and lacustrine sediments determined in the study area indicate that precipitation probably occurred due to climate fluctuations ranging from arid and semi-arid to wet conditions.

KARACAÖREN YÖRESİ (NEVŞEHİR) DİATOMİTLERİNİN FİZİKOKİMYASAL ÖZELLİKLERİ VE KULLANIM ALANLARI

Bu calismada, Nevsehir ili, Urgup ilcesi, Karacaoren Yoresi’nde yuzeylenen ve Orta Anadolu Volkanizmasina bagli olarak olusan diyatomitlerin fizikokimyasal ozellikleri ve kullanim alanlari arastirilmistir. Inceleme alaninda, birisi Kuvaterner yasli gol cokelleri icerisinde (K1), digeri gec Miyosen- Pliyosen yasli Urgup formasyonu’nun Bayramhacili uyesi icerisinde yer alan gol cokellerinden (K2) olmak uzere 2 adet stratigrafik kesit olculmustur. Inceleme alaninda yer alan diyatomitlerin fizikokimyasal ozelliklerini ve kullanim alanlarini belirlemek amaciyla araziden alinan orneklere Maden Tetkik ve Arama Genel Mudurlugu (MTA) Laboratuvari’nda ates kaybi (1050 °C de), XRD, asitte ve suda cozunmeyen madde miktari, isi iletkenligi (101; 150 °C de ve ± 10 °C de), XRF, pH, toplam gozeneklilik, yogunluk, ozgul yuzey alani, gozenek hacmi, gozenek boyutu, beyazlik, dane boyu ve SEM analizleri yaptirilmis, analiz sonuclarinin degerlendirilmesi sonucunda, calisilan diyatomitlerin ticari degerlerinin oldugu, suzuculerde, dolgu ve yapi maddesi olarak ve silikat imalatinda dogrudan, hafif asindirici ve temizleyici olarak ve yalitim maddesi yapiminda ise isleme tabii tutularak kullanilabilecekleri ortaya konulmustur.