Genesis of the hydrothermal Karaçayır kaolinite deposit in Miocene volcanics and Palaeozoic metamorphic rocks of the Uşak-Güre Basin, western Turkey

The Karaçayır kaolinite deposit, situated in the Uşak-Güre basin of western Turkey, is hosted by rhyolite and andesite of the Miocene Dikendere volcanics, and by muscovite schist, glaucophane schist, talc schist and chlorite schist of the Palaeozoic Eşme Formation.

Turkish Journal of Earth Sciences http://journals.tubitak.gov.tr/earth/ Research Article Turkish J Earth Sci (2013) 22: 444-468 © TÜBİTAK doi:10.3906/yer-1112-2 Genesis of the hydrothermal Karaỗayr kaolinite deposit in Miocene volcanics and Palaeozoic metamorphic rocks of the Uşak-Güre Basin, western Turkey Selahattin KADİR*, Hülya ERKOYUN Department of Geological Engineering, Eskişehir Osmangazi University, TR-26480 Eskişehir, Turkey Received: 05.12.2011 Accepted: 02.07.2012 Published Online: 06.05.2013 Printed: 06.06.2013 Abstract: The Karaỗayr kaolinite deposit, situated in the Uak-Gỹre basin of western Turkey, is hosted by rhyolite and andesite of the Miocene Dikendere volcanics, and by muscovite schist, glaucophane schist, talc schist and chlorite schist of the Palaeozoic Eşme Formation The association of kaolinization with silicification and Fe-oxidation, and the presence of pyrite, chalcopyrite and gypsum, suggest that hydrothermal alteration processes in the volcanics and schists were controlled by faults Thus, prevalent kaolinite is associated with quartz, smectite, illite and opal-CT in the centre of the deposit, with relative increases in smectite, illite, chlorite and Fe (oxyhydr) oxide phases outwards and upwards Texturally, sanidine and plagioclase crystals are sericitized and kaolinized in rhyolite and andesite respectively, whereas muscovite, chlorite and feldspar in schists exhibit partial kaolinization and illitization Micromorphologically, authigenic kaolinite, having hexagonal book-like and vermiform textures, occurs as rims on feldspar, muscovite and chlorite suggesting a dissolution-precipitation mechanism Pyrite, locally transformed to hematite, is euhedral to subhedral, with grain sizes of ±400 µm Iron occurs as Fe2+ and Fe3+ within the structures of the Karaỗayr kaolinites and smectites, as determined by Mössbauer spectroscopy Enrichment of Mg, Ca and Fe in the kaolinite deposit is related to the presence of smectite, calcite, dolomite, pyrite ± chalcopyrite, goethite and hematite Kaolinized volcanic and schist samples from the Karaỗayr area are characterized by 35.77-87.58% SiO2, 3.2722.83% Al2O3, 0.91-9.16% Fe2O3, 0.01-5.94% K2O and 0.26-12.41% MgO, revealing moderate degrees of kaolinization ± illitization ± smectitization coexistent with high degrees of silicification and Fe (oxyhydr)oxidation Increases of Fe2O3, MgO, CaO and Zr and decreases of Rb, Sr, and Ba (except for decreases in partially altered volcanics) in kaolinite samples adjacent to schists and volcanic rocks suggest that kaolinite developed by alteration of both schists and volcanics The Karaỗayr kaolinite and smectite have 18O and δD values ranging from 11.6 to 20.4‰, and -79‰ to -112‰, respectively Using the isotopic fractionation factor (α), the temperatures of formation for the Karaỗayr kaolinite and smectite were determined to be 61.6-131.7 °C and 61.2-148.9 °C, respectively, and negative δ34S values for pyrite, chalcopyrite and gypsum reflect formation under the influence of hydrothermal activity; this assumption is supported by isotope equilibrium temperatures of 80-125 °C calculated from pyrite-chalcopyrite pairs Thus, the Karaỗayr kaolinite deposit formed by an increase in Al±Fe/Si under acidic environmental conditions, which facilitated epithermal alteration of feldspar and volcanic glass in volcanic rocks, and muscovite, chlorite and feldspar in schists, controlled by tectonic activity during Miocene volcanism Key Words: Uşak, hydrothermal alteration, kaolinite, Miocene volcanites, Palaeozoic metamorphics, mineralogy, geochemistry, stableisotope geochemistry Introduction Hydrothermal kaolinite deposits in Turkey typically occur within volcanics (Seyhan 1978; Sayın 2007; Ece & Schroeder 2007; Ece et al 2008; Erkoyun & Kadir 2011; Kadir et al 2011) Occurrences of hydrothermal kaolinite in metamorphic rocks are scarce (Kadir & Akbulut 2009) Hydrothermal kaolinite deposits generally develop under the control of an active tectonic environment and with the presence of permeable units so that hydrothermal fluids can be flushed through igneous or metamorphic rocks (Murray & Keller 1993) The Karaỗayr kaolinite deposit is of economic importance, with approximately one million tonnes of * Correspondence: skadir_esogu@yahoo.com 444 reserves (8th Five-Year Development Plan – State Planning Organisation of Turkey 2001), and is developed in both volcanic rocks (rhyolite and andesite) and metamorphic rocks (muscovite schist, glaucophane schist, talc schist and chlorite schist) by hydrothermal alteration under the control of tectonic activity To date, the geology, mineralogy, geochemistry and technological properties of the Karaỗayr kaolinite deposit have been studied (Seyhan 1972; Karaaaỗ 1975, Karaaaỗ et al 1975, Fujii et al 1995) Furthermore, the region has been studied for its Quaternary thermal water (Davraz 2008); the distribution of thermal waters in Turkey is controlled by fault systems and proximity KADİR and ERKOYUN / Turkish J Earth Sci to Tertiary-Quaternary volcanics (Mutlu & Gỹleỗ 1998) Although Kadir & Akbulut (2009) studied the mineralogy, geochemistry and genesis of the Taşoluk kaolinite deposit in the Afyonkarahisar (western Anatolia) area, which developed in both pre-Early Cambrian sericitic micachlorite schist and Neogene volcanics, there have been no detailed micromorphological (transmission electron microscopy), 57Fe Mössbauer spectroscopic, geochemical (modelling of mass gains and losses of major-, trace- and rare-earth elements during alteration), and kaolinitefraction stable-isotopic (including calculation of formation temperatures) studies of the Karaỗayr kaolinite deposits, which are related to Palaeozoic mica schist, glaucophane schist, talc schist, calcareous schist and chlorite schist The object of the present study was to investigate in detail the geological, mineralogical and geochemical aspects, as well as the genesis, of this hydrothermal kaolinite deposit within Miocene volcanics and Palaeozoic metamorphic rocks, and to demonstrate the significance of these data and their interpretation as important tools in future exploration for tectonic-controlled hydrothermal-alteration systems and related kaolinite deposits throughout Anatolia Geology and general features of the Karaỗayr deposit The basement rocks of the area comprise talc schist, mica schist, glaucophane schist, chlorite schist and calcareous schist (Eşme Formation) of Palaeozoic age (Ercan et al 1977) These units are overlain unconformably by lacustrine sediments of the Early Miocene Hacıbekir group [the Kürtköyü (exposed outside the study area) and Yeniköy formations], comprising conglomerate, claystone, sandstone, dolomitic marble and thin layers of tuff and tuffite, with cross-cutting rhyolite, rhyodacitic lavas and related tuffs, the latter collectively termed the Dikendere volcanics (Figures and 2) The research of Seyitoğlu (1997) included K-Ar dating (20-18.9 Ma) of volcanic samples from the Hacıbekir group, indicating an Early Miocene age These units are unconformably overlain by the Middle Miocene İnay group, comprising the Ahmetler formation (conglomerate, claystone, siltstone), the Beydağ volcanics (andesitic to rhyolitic lavas and pyroclastic deposits), the Ulubey formation (lacustrine limestone), and the Payamtepe volcanics (lava flows and dykes) (Karaoğlu et al 2010) The Ahmetler, Ulubey and Payamtepe formations are exposed outside the study area 40Ar/39Ar radiometric data from biotite, amphibole and sanidine crystals and groundmass (12.15±0.15–17.29±0.13 Ma) of the İnay group suggest an Early-Middle Miocene age (Karaoğlu et al 2010) These units are overlain unconformably by the Upper Miocene Asartepe formation, comprising fluvial conglomerate, sandstone, and, locally, marl and limestone Seyitoğlu et al (2009) reported a biostratigraphic and magnetostratigraphic age of Ma for the Asartepe formation All of the aforementioned units are overlain unconformably by Quaternary fluvial alluvium The Karaỗayr kaolinite deposit developed within both Palaeozoic metamorphics and Miocene volcanics controlled by an NE-SW-oriented normal fault zone part of the tectonic regime in the Uşak-Güre basin This basin possibly developed during and after collision of the Arabian and Eurasian plates, with subduction of the African plate under the Aegean-Anatolian plate along the Hellenic and Cyprean trenches, and following back-arc spreading (Ring & Layer 2003; Ring et al 2010; Karaoğlu et al 2010) (Figure 1) This deposit comprises a silicified kaolinite zone, an illitic-smectitic zone, an Fe (oxyhydr) oxide zone, and silicified and Fe-oxidation zones, and is hosted by volcanic rocks (rhyolite and andesite) and metamorphic rocks (talc schist, mica schist, chlorite schist and glaucophane schist) as controlled by the tectonic regime (Figure 3a-e) The silicified kaolinite zone at the centre of the deposit is white and is vertically and laterally transitional into altered volcanics and schists The kaolinite zone encloses irregular grey illite, brown smectite, and silica lenses (Figure 3f,g) Locally, manganese (oxyhydr) oxide impregnation also is present within the kaolinized zone and, locally, as 1–10-mm-thick coatings on schists (Figure 3h) The volcanics and metamorphics are characterised by moderate to high degrees of alteration Talc schist locally encloses Fe (oxyhydr)oxide phases and disseminated pyrite and chalcopyrite Glaucophane schist is dark blue and moderately hard A yellowish-brown Fe (oxyhydr)oxide zone locally containing gypsum crystals is located in the upper part of the illitic-smectitic zone and alternates with it (40 cm to m thick) A dark-brown silicified and Fe (oxyhydr)oxide zone is situated on top of the deposit as silicic and Fe-oxidised horizons (~5 m) Silicification and Fe (oxyhydr)oxide phases are abundant within the Karaỗayr kaolinite deposit Methods In order to identify the lateral and vertical distribution of kaolinite and coexisting clay and non-clay minerals, the volcanics and metamorphics of the Karaỗayr kaolinite deposit were sampled (Figures and 2) One hundred and forty samples, reflecting various degrees of alteration, were analysed via polarised-light microscopy (Leitz Laborlux 11 Pol), polished-section microscopy (Leitz MPV-SP), X-ray powder diffractometry (XRD) (Rigaku-Geigerflex), scanning electron microscopy (SEM-EDX) (JEOL JSM 84A-EDX), and transmission electron microscopy (TEM) (JEOL JEM-21007) in order to determine their mineralogical characteristics XRD analyses were performed using CuKα radiation and a scanning speed of 1° 2θ/min Randomly selected powders of whole-rock samples were used to determine 445 KADİR and ERKOYUN / Turkish J Earth Sci N Mezarardı Srt Gỹney Elence Karaỗayr Koca Tepe Paaclar Cierdede km UŞAK AEGEAN SEA BLACK SEA ANKARA KÜTAHYA T U R K E Y UŞAK Study area 100 km metagranite high-angle normal fault Asartepe Formation Upper Karaỗayr kaolinite deposit undifferentiated continental clastic rock continental carbonate rocks andesite, rhyolite and pyroclastic rocks Beydağ volcanites rhyolite, rhyodacite.tuff and agglomerate Dikendere volcanites continental clastic rocks Yeniköy Formation Hacıbekir Group İnay Group schist Miocene Middle Palaeozoic marble alluvium Lower ophiolite Musadağı Vezirler Eşme Formation marble mélange Mesozoic EXPLANATION Quaternary MEDITERRANEAN SEA SEA MEDITERRANEAN undefined fault residential area Figure Geological map of the Karaỗayr kaolinite deposit and surrounding area (modified from Akdeniz & Konak 1979; Karaoğlu et al 2010) 446 R LITHOLOGY EXPLANATION Upper 0-30 E AT QU THICKNESS (m) MEMBER FORMATION GROUP SERIES SYSTEM UPPER SYSTEM KADİR and ERKOYUN / Turkish J Earth Sci Middle MIOCENE NEOGENE TERTIARY CENOZOIC unconformity UPPER US EO ET AC CR PERMOTRIASS PALAEOZOIC MESOZOIC Lower unconformity Vezirler mélange ophiolitic mélange unconformity marble Figure Simplified general stratigraphic section for the study area (modified from Akdeniz & Konak 1979; Karaoğlu et al 2010) 447 KADİR and ERKOYUN / Turkish J Earth Sci illite silica cap + Fe (oxyhydr)oxide kaolinite + Fe (oxyhydr)oxide kaolinite smectite+illite 10 m a b 1m kaolinised andesite altered schist c d 1m altered schist smectite kaolinite e 0.5 m f kaolinite illite manganese (oxyhydr)oxide kaolinite g 20 cm h 2m Figure Field photographs: a a general view of the Karaỗayr kaolinite deposit; b a close-up view of an illite lens and Fe (oxyhydr)oxide-bearing phases in kaolinized units outward from the kaolinite deposit; c a close-up view of kaolinized andesite in the kaolinite deposit; d a close-up view of partially altered schist; e a close-up view of altered schist; f a smectite lens developed within the kaolinite unit; g an illite nodule developed within the kaolinized unit; h manganese (oxyhydr)oxide minerals developed within the kaolinized unit 448 KADİR and ERKOYUN / Turkish J Earth Sci bulk mineralogy Clay mineralogy was determined via separation of the clay fraction (