Kaolin Occurrences in the Erenler Dagi Volcanics,Southwest Konya Province,Turkey |
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| Abstract: | Mainly calc-alkaline, andesitic, and dacitic volcanics from different late Miocene-Pliocene eruption centers crop out WSW of Konya, and locally are interbedded with lacustrine sediments. Hydrothermal alteration within these rocks is widespread. In addition to kaolinite, other major alteration products include halloysite, alunite, cristobalite, quartz, illite, montmorillonite, and zeolitegroup minerals. Based on the cristobalite-quartz relationship, the kaolinization temperature is estimated as ～100°C. The samples were mineralogically and chemically examined using XRD, SEM-EDS, IR, DTA-TG, and XRF. The crystallinity of the kaolinite is moderate, and shows structural disorder. Both the kaolinite and halloysite are almost stoichometric. Kaolinization generally led to Al2O3 increases and release of alkalies, alkaline earths, most of the Fe2O3, and SiO2. SiO2 and Al2O3 contents are low, and LOI is very high for halloysite deposits relative to kaolin occurrences. The kaolinite-alunite assemblages indicate that pH of the altering solutions initially was ～4. SEM investigation demonstrates that kaolinite has booklet texture, whereas halloysite is acicular to needleshaped. The chemical, mineralogic, and firing properties of the kaolin deposits are appropriate for use as refractory raw material. The Erenler Dagi kaolin deposits are excellent examples of the acid-sulfate type of hydrothermal alteration. The findings of the study may be useful in exploration for similar hydrothermal mineral occurrences worldwide. |
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