Conference Presentations by Nihal Cevik
2019-2020 YILI KÜLTEPE-KANİŞ KAZILARI, 2022
Papers by Nihal Cevik
Türkiye jeoloji bülteni, Dec 1, 2011
Yozgat-Yerkoy- Belkavak koyu civarinda yuzeyleyen volkanik kayaclardan bazaltik andezitler icinde... more Yozgat-Yerkoy- Belkavak koyu civarinda yuzeyleyen volkanik kayaclardan bazaltik andezitler icinde kalsedon, beyaz kuvars, seffaf kuvars-I, ametist ve seffaf kuvars-II minerallerinden olusan bes ayri silis zonu bulunmustur. Bu zonlarin olusum evrelerine gore sirasi, homojenlesme sicakliklari ve % NaCl esdegeri olarak tuzluluk parametreleri belirlenmeye calisilmistir. Buna gore, ilk evre kalsedon bantlarindan olusmaktadir. Bunlar kriptokristalen dokuda oldugundan herhangi bir sivi kapanima rastlanmamistir. Daha sonra olusan beyaz kuvarslarda olculen sicakliklar 272-323 °C arasinda, tuzluluklar ise 3.86 - 4.65 % NaCl esdegerlerindedir. Şeffaf kuvars-I evresinde ise 217-280°C arasi sicakliklar belirlenirken, tuzluluklar 3.06-4.96 % NaCl esdegerleri olarak olculmustur. Ametistlerin olustugu sirada cozeltilerin sicakliklari 162-370°C arasinda ve tuzluluklari da 1.73-4.96 % NaCl esdegerlerindedir. Son evredeki seffaf kuvars-II olusumlari ise 120-270 °C arasinda sicakliklar vermektedir. Tuzluluklar ise 0-6.88 % NaCl esdegerleri arasindadir. Elde edilen bu verilere gore ortama gelen ilk silisli cozeltiler nispeten soguk bir ortam ile temasta olduklarindan kalsedonlari olusturmuslardir. Daha sonra gelmeye devam eden silisli cozeltilerin sicakligi 200-370 °C’ lere kadar cikmis ve zamanla sicakliklari azalarak 120 °C’lere kadar dustugu tespit edilmistir. Genellikle % 8’in altindaki tuzluluk degerleri kuvars ve ametistlerin olusumlari sirasinda deniz suyunun yani sira meteorik sularin da etkin olabilecegini dusundurmektedir.
Bulletin of the mineral research and exploration, May 25, 2016
Dutluca volcanics, which are known as Hallaçlar Formation in regional scale in the study area (Ku... more Dutluca volcanics, which are known as Hallaçlar Formation in regional scale in the study area (Kurshensky, 1976), are composed of hydrothermally altered andesite and basaltic andesite. In these rocks, sulfidic minerals such as pyrite, enargite and chalcosine, and oxide and hydroxide minerals such as magnetite, hematite and goethite were detected as opaque minerals. The presence of enargite in opaque mineral paragenesis, and the changes observed in structures and textures of opaque and silicate minerals indicate that examined volcanics have been altered by highly sulfidic hydrothermal solutions. During the hydrothermal alteration process, which indicates at least in two phases, a diffuse pyritization rich in H 2 S in reducing conditions and enargite mineral, which is known as pathfinder minerals in such processes, formed in the first phase. Later on; the extensive martitization developed in oxidizing conditions.
DergiPark (Istanbul University), Jun 1, 2017
We investigate rare earth element geochemistry, microthermometric characteristics, and radiogenic... more We investigate rare earth element geochemistry, microthermometric characteristics, and radiogenic isotope systematics of fluorites and stable isotope compositions of gangue minerals from several fluorite deposits in central Turkey. In the deposits, fluorite is the main ore mineral and it is accompanied by quartz, calcite, and minor pyrite and barite. Veins are represented by three different fluorite types based on their color. Total REY contents of fluorites are highly variable, ranging from 24 to 693 ppm. LREE concentrations of fluorites of all colors are similar but medium and heavy REE abundances of green fluorites are nearly an order of magnitude greater than in both host rocks and purple and yellow fluorites, indicating multiple sources for crystallization. REEs show significant fractionation and purple fluorites with relatively low HREE contents were likely precipitated at an earlier stage. As crystallization continued, green fluorites were nucleated because of ion exchange of LREEs with the host rock/minerals. Fluid inclusions yielded a wide range of homogenization temperatures from 86 °C to 292 °C and salinities from 0 to 20 wt.% NaCl equiv. The 87 Sr/ 86 Sr ratios of fluorites, varying from 0.707627 to 0.709380, overlap with the range of host rocks. 143 Nd/ 144 Nd values suggest two populations: purple fluorites with less radiogenic and green fluorites with more radiogenic Nd isotope ratios. The Sr-Nd isotope systematics of Bayındır fluorites are consistent with that of the Bayındır syenite, indicating that hydrothermal solutions progressively reacted with the host rock until equilibrium was established. δ 18 O values of quartz are slightly higher than the magmatic range. δ 13 C and δ 18 O of calcites fall into the range of marine carbonates. δ 34 S values of barites indicate derivation from diverse reservoirs changing from marine to terrestrial sources. In contrast, sulfur in pyrites points to a magmatic origin. Therefore, is it suggested that magmatic fluids to some extent contributed to the precipitation of fluorite veins.
Yozgat –Yerkoy – Belkavak Koyu civarinda volkanik kayaclar icinde kalsedon, kuvars ve ametist olu... more Yozgat –Yerkoy – Belkavak Koyu civarinda volkanik kayaclar icinde kalsedon, kuvars ve ametist olusumlari izlenmektedir. Mineralojik, petrografik ve jeokimyasal calismalar sonucu inceleme alaninda andezit (bazaltik andezit-?), killesmis camsi tuf, riyodasit/dasit ve aglomeralar ayirtlanmis ve haritalanmistir. Ayrica inceleme alaninda izlenen fosilli kumlu kirectaslarinda Bartoniyen katini veren mikrofosiller saptanmistir. Andezitik lavlarin sig denizel ortama cok evreli olarak aktiklari ve her evre arasinda alterasyon gecirdikleri dusunulmektedir. Bu kayaclarda izlenen yesil renkli alterasyon damar ve zonlarinda polarizan ve cevher mikroskobisi, X-Isinlari kirinim ve Raman Spektrografisi calismalari ile saptanan seladonit, fillipsit, smektit, hematit ve kalsit parajenezi denizalti ortaminda 100°C’nin (olasilikla da 40°C’nin) altinda dusuk sicaklik hidrotermal alterasyonu sureclerini gecirdiklerine isaret etmektedir. Yapilan jeokimyasal calismalar bu alterasyon surecleri sirasinda SiO2, MgO, Fe2O3, K2O, Rb, Cs ve U degerlerinde belirgin zenginlesmeler ancak Al2O3, CaO, Na2O, MnO, Ba, Sr, Zr ve Y degerlerinde onemli azalmalar oldugunu gostermistir.Genellikle kalsedon yer yer de onlara eslik eden kuvars ve ametistlerden olusan silis damarlari andezit, altere andezit, seladonitli yesil renkli alterasyon damarlari ve killesmis camsi tufleri kesmektedir. Aglomeralar icinde kayac parcalari ile birlikte bulunmaktadir.Kuvars ve ametistlerde yapilan sivi kapanim calismalari kalsedonik evreden sonra kuvars olusumlari evrelerinde silisli cozeltilerin isisinin 200°C’lerden 370°C’lere kadar ciktigini ve sonra 120°C’lere kadar dustugunu gostermistir. Genellikle %8’in altindaki tuzluluk oranlari kuvars ve ametistlerin olusumlari sirasinda meteorik sularin etkili oldugunu gostermektedir. Sonuc olarak bu olusumlarin olasilikla riyodasit/dasit volkanizmasindan sonraki artik silisli cozeltilerin sig denizel fasiyesten sonra karasal ortam kosullarinda kirik ve catlaklara yerlestigini dusundurmektedir.Abstract Chalcedony, quartz and amethyst crystals are observed in volcanic rocks around Belkavak village of Yerkoy town in Yozgat. Andesite (basaltic andesite-?), argillized vitric tuff, rhyodacite /dacite and agglomerate are determined by mineralogical, petrographical and geochemical studies and are mapped. Microfossils indicating Barthonien age are found in fossillized sandy limestones in the study area.It is considered that multi phase andesitic lavas are flown into shallow seawater and between each flow phase an alteration period is developed. Green colored alteration veins and zones in these rocks are characterized by celadonite, phillipsite, smectite, hematite and calcite paragenesis which are determined by polarizan and ore microscopical, XRD and Raman Spektrographical studies. This paragenesis point out low temperature hydrothermal alteration processes run below 100°C (probably 40°C) temperatures under submarine environment. Geochemical studies revealed that SiO2, MgO, Fe2O3, K2O, Rb, Cs and U enrichments but Al2O3, CaO, Na2O, MnO, Ba, Sr, Zr and Y depletions in green colored alteration veins during the alteration processes. Siliceous veins including mainly chalcedonic formations accompanied by sparsely quartz and amethyst crystals cut andesite, altered andesite, green colored alteration veins and argillized vitric tuffs, but are found as veins in volcanic rock fragments of agglomerates. Fluid inclusion studies carried out on quartz and amethyst crystals show that the heat of siliceous solutions after chalcedonic phase should rise from 200°C to 370°C and afterwards decreased to 120°C. Salinities generally under 8% point out that meteoric water were the dominant water in the environment during the formation of quartz and amethysts. Consequently, siliceous solutions occur as relict solutions after rhyodacitic /dacitic volcanism which have been brought to the fractures and cracks of andesites and tuffs under continental environment conditions after submarinal basins have been ceased.
Inceleme alani Burhaniye (Balikesir) ilcesinin 10 km guneyinde Dutluca koyu cevresindedir. Bu bol... more Inceleme alani Burhaniye (Balikesir) ilcesinin 10 km guneyinde Dutluca koyu cevresindedir. Bu bolgedeki Miyosen andezitik-dasitik volkanitlerinde yaygin olan hidrotermal alterasyonlar incelenerek, mineral bilesenlerindeki donusumler, donusumu saglayan cozeltilerin turu (dusuk ya da yuksek sulfidasyonlu) ve kokeni, kayaclarin kimyasal bilesimlerindeki degisiklikler (ana oksit ve eser element degisimleri), nadir toprak elementleri (NTE)bolluk ve anomalileri belirlenmistir. Boylece inceleme alanindaki hakim alterasyonlar ayirt edilmistir. Bu calismalari gerceklestirmek icin oncelikle mineralojik-petrografik, bunun paralelinde/ardindan jeokimyasal incelemeler yapilmistir. Bu kapsamda orneklerin ana ve eser element icerikleri, bunlarin korelasyonlari, bolluklari ve anomalileri belirlenmis, ayrica izotop calismalari ile hidrotermal cozeltilerin tipi ve kaynagi hakkinda bilgiler elde edilmistir. Mineralojik incelemelere gore, Dutluca bolgesindeki volkanitlerde gelisen alterasyonlar hakkinda iki farkli ortam yorumu yapilabilmektedir. Birincisi, alunit, kaolinit, hematit, gotit ve jarositin mineral birlikteligine sahip, su tablasinin ustunde, pirit oksidasyonu ile olusmus superjen ortamdir. Digeri ise AAK’dan SZK grubuna dogru belirgin olarak gozlenen aluminyum hareketliligi, kuvars-alunit, kuvars-kaolinit birliktelikleridir ki, bunlar magmatik hidrotermal ortami isaret etmektedir. Opak mineral parajenezi (parajenezde enarjit bulunmasi), opak ve opaklasma gosteren silikat minerallerinin donusumunu yansitan yapi ve dokulari, incelenen volkanitlerin yuksek sulfidasyonlu hidrotermal cozeltiler tarafindan altere edildigini gostermektedir. Elementlerin korelasyon iliskileri ve olusturduklari element gruplari SiO2 ve ona bagli elementlerle Al2O3 ile birlikte hareket eden elementler olarak goze carpmaktadir. Silisin diger ana elementlerden farkli bir faz oldugu ve Au’un bu fazla ilgili oldugu gorulmektedir. Incelenen orneklerde gorulen jeokimyasal egilimler; AAK'dan SZK'a dogru, yani alterasyon artma derecesine bagli olarak K ve Zn giderek azalmasi asit cozeltilerin etkisini isaret etmektedir. Basta Au olmak uzere, Mo ve Pb Dutluca volkanitlerinde SZK’ya dogru onemli derecede artis gostermektedir. Kayac turlerinin ve yataklarin δ34S degerleri ile calisma alanindaki sulfid ve sulfat minerallerinin izotop degerleri karsilastirilmasindan elde edilen verilere gore inceleme alaninda belirlenen halotrikit, alunit, jarosit, piritlere ait δ34S kukurt izotopunun epitermal yataklara uyumlu oldugu gorulmektedir.2Sonuc olarak, incelenen bolgede epitermal bir sistem gelismis ve buradaki alterasyonlarin olusmasinda yuksek sulfidasyonlu hidrotermal cozeltilerin etkili oldugu belirlenmistir.AbstractThe study area is located around the Dutluca village 10 km south of Burhaniye (Balikesir) town. We investigate hydrothermal alteration in Miocene andesitic-dacitic volcanites and changes in mineral composition and type and origin of fluids (e.g. low or high-sulfidation) which drive these transformations, changes in chemical composition of rocks (major oxide and trace element variations) and abundances and anomalies of rare earth elements. Thus characteristic alterations in the area were identified. For this purpose, mineralogic-petrographic and geochemical studies were implemented. Major oxide and trace element compositions and their correlations, abundances and anomalies were determined and type and source of hydrothermal fluids responsible for mineralization were identified. Results of mineralogical studies indicate the presence of two different alteration types. The first is a supergene environment above the water table is formed by oxidation of pyrite and represented by alunite, kaolinite, goethite and jarosite. The second is discrete with aluminum mobility and represented by quartz-alunite and quartz-kaolinite assemblages from AAK to SZK group indicating a magmatic hydrothermal environment. Opaque mineral paragenesis (the presence of enargite) and texture and structures reflecting transformation of silicate minerals yield that studied volcanites are altered by high-sulfidation hydrothermal solutions. Variations in REE contents indicate silicic and advanced argillic alteration. LREE enrichment in samples are explained by alunite and jarosite formation whilst negative Eu anomalies are attributed to plagioclase alteration induced by high acidity and abundance of Cl, F and SO4 complex ions in hydrothermal fluids. Correlation relations among the elements and element groups formed are associated with SiO2 and other elements that behave in the same manner with Al2O3. Silica is found to behave different from other major elements and Au is closely related with silica. Geochemical trends in studied samples indicate a gradual decrease in K and Zn contents depending on increasing degree of alteration from AAK to SZK. In Dutluca volcanites Mo, Pb and especially Au concentrations are significantly increased towards SZK. Comparison of δ34S values of…
Inceleme alani Burhaniye (Balikesir) ilcesinin 10 km guneyinde Dutluca koyu cevresindedir. Miyose... more Inceleme alani Burhaniye (Balikesir) ilcesinin 10 km guneyinde Dutluca koyu cevresindedir. Miyosen andezitik-trakiandezitik volkanitlerinde yaygin olan hidrotermal alterasyonlar incelenerek, mineral bilesenlerindeki donusumler, donusumu saglayan cozeltilerin turu ve kokeni, kayaclarin kimyasal bilesimlerindeki degisiklikler bolluk ve anomalileri belirlenmistir. Boylece inceleme alanindaki hakim alterasyonlar ayirt edilmistir. Dutluca bolgesindeki volkanitlerde gelisen alterasyonlar hakkinda iki farkli ortam yorumu yapilabilmektedir. Birincisi, alunit, kaolinit, hematit, gotit ve jarositin mineral birlikteligine sahip, su tablasinin ustunde, pirit oksidasyonu ile olusmus superjen ortamdir. Digeri ise az altere kayac (AAK)’dan silisce zengin kayac (SZK) grubuna dogru belirgin olarak gozlenen aluminyum hareketliligi, kuvars-alunit, kuvars-kaolinit birliktelikleridir ki, bunlar magmatik hidrotermal ortami isaret etmektedir. Opak mineral parajenezi (parajenezde enarjit bulunmasi), opak ve opaklasma gosteren silikat minerallerinin donusumunu yansitan yapi ve dokulari, incelenen volkanitlerin yuksek sulfidasyonlu hidrotermal cozeltiler tarafindan altere edildigini gostermektedir. Elementlerin korelasyon iliskileri ve olusturduklari element gruplari SiO2 ve ona bagli elementlerle Al2O3 ile birlikte hareket eden elementler olarak goze carpmaktadir. Silisin diger ana elementlerden farkli bir faz oldugu ve Au’un bu fazla ilgili oldugu gorulmektedir. Incelenen orneklerde gorulen jeokimyasal egilimler; AAK'dan SZK'a dogru, yani alterasyon artma derecesine bagli olarak K ve Zn’nin giderek azalmasi asitli cozeltilerin etkisini isaret etmektedir. Basta Au olmak uzere, Mo ve Pb Dutluca volkanitlerinde SZK’ya dogru onemli derecede artis gostermektedir. Sulfid ve sulfat minerallerinin δ34S izotop degerleri incelendiginde epitermal yataklarla uyumlu oldugu gorulmektedir. Ayrica izotop verileri calisma alaninda superjen ve magmatik hidrotermal olmak uzere iki alterasyon sureci gelistigini gostermektedir. Sonuc olarak, incelenen bolgede epitermal bir sistem gelismis ve alterasyonlarin olusmasinda yuksek sulfidasyonlu hidrotermal cozeltilerin etkili oldugu belirlenmistir.AbstractThe study area is located around the Dutluca village 10 km south of Burhaniye (Balikesir) town. We investigate hydrothermal alteration in Miocene andesitic-dacitic volcanites and changes in mineral composition and type and origin of fluids which drive these transformations, changes in chemical composition of rocks, abundances and anomalies of rare earth elements. Thus characteristic alterations in the area were identified. There are two different interpretations of the alterations in the volcanic rocks of Dutluca region. The first is a supergene environment above the water table is formed by oxidation of pyrite and represented by alunite, kaolinite, goethite and jarosite. The second is discrete with aluminum mobility and represented by quartz-alunite and quartz-kaolinite assemblages from AAK to SZK group indicating a magmatic hydrothermal environment. Opaque mineral paragenesis (the presence of enargite) and texture and structures reflecting transformation of silicate minerals yield that studied volcanites are altered by high-sulfidation hydrothermal solutions. Variations in REE contents indicate silicic and advanced argillic alteration. LREE enrichment in samples are explained by alunite and jarosite formation whilst negative Eu anomalies are attributed to plagioclase alteration induced by high acidity and abundance of Cl, F and SO4 complex ions in hydrothermal fluids. Correlation relations among the elements and element groups formed are associated with SiO2 and other elements that behave in the same manner with Al2O3. Silica is found to behave different from other major elements and Au is closely related with silica. Geochemical trends in studied samples indicate a gradual decrease in K and Zn contents depending on increasing degree of alteration from AAK to SZK. In Dutluca volcanites Mo, Pb and especially Au concentrations are significantly increased towards SZK. When the δ34S isotopic values of the sulfide and sulfate minerals are examined, it is seen to be compatible with the epithermal deposits. In addition, isotope data indicate that two alteration processes which are supergene and magmatic hydrothermal alteration have evolved in the study area. As a result, an epithermal system was formed in the studied area and high-sulfidation hydrothermal solutions played an important role in formation of alteration.
TURKISH JOURNAL OF EARTH SCIENCES, 2017
We investigate rare earth element geochemistry, microthermometric characteristics, and radiogenic... more We investigate rare earth element geochemistry, microthermometric characteristics, and radiogenic isotope systematics of fluorites and stable isotope compositions of gangue minerals from several fluorite deposits in central Turkey. In the deposits, fluorite is the main ore mineral and it is accompanied by quartz, calcite, and minor pyrite and barite. Veins are represented by three different fluorite types based on their color. Total REY contents of fluorites are highly variable, ranging from 24 to 693 ppm. LREE concentrations of fluorites of all colors are similar but medium and heavy REE abundances of green fluorites are nearly an order of magnitude greater than in both host rocks and purple and yellow fluorites, indicating multiple sources for crystallization. REEs show significant fractionation and purple fluorites with relatively low HREE contents were likely precipitated at an earlier stage. As crystallization continued, green fluorites were nucleated because of ion exchange of LREEs with the host rock/minerals. Fluid inclusions yielded a wide range of homogenization temperatures from 86 °C to 292 °C and salinities from 0 to 20 wt.% NaCl equiv. The 87 Sr/ 86 Sr ratios of fluorites, varying from 0.707627 to 0.709380, overlap with the range of host rocks. 143 Nd/ 144 Nd values suggest two populations: purple fluorites with less radiogenic and green fluorites with more radiogenic Nd isotope ratios. The Sr-Nd isotope systematics of Bayındır fluorites are consistent with that of the Bayındır syenite, indicating that hydrothermal solutions progressively reacted with the host rock until equilibrium was established. δ 18 O values of quartz are slightly higher than the magmatic range. δ 13 C and δ 18 O of calcites fall into the range of marine carbonates. δ 34 S values of barites indicate derivation from diverse reservoirs changing from marine to terrestrial sources. In contrast, sulfur in pyrites points to a magmatic origin. Therefore, is it suggested that magmatic fluids to some extent contributed to the precipitation of fluorite veins.
Bulletin Of The Mineral Research and Exploration, 2016
Dutluca volcanics, which are known as Hallaçlar Formation in regional scale in the study area (Ku... more Dutluca volcanics, which are known as Hallaçlar Formation in regional scale in the study area (Kurshensky, 1976), are composed of hydrothermally altered andesite and basaltic andesite. In these rocks, sulfidic minerals such as pyrite, enargite and chalcosine, and oxide and hydroxide minerals such as magnetite, hematite and goethite were detected as opaque minerals. The presence of enargite in opaque mineral paragenesis, and the changes observed in structures and textures of opaque and silicate minerals indicate that examined volcanics have been altered by highly sulfidic hydrothermal solutions. During the hydrothermal alteration process, which indicates at least in two phases, a diffuse pyritization rich in H 2 S in reducing conditions and enargite mineral, which is known as pathfinder minerals in such processes, formed in the first phase. Later on; the extensive martitization developed in oxidizing conditions.
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Conference Presentations by Nihal Cevik
Papers by Nihal Cevik