Hydrothermal alteration led to development of the Yarıkçı clay deposit within the Mesozoic chlorite-, muscovite-, chlorite-muscovite-schist, and garnet-graphite phyllite units along NW–SE- and N–S-trending faults in Mihalıççık in western central Anatolia. The geological, mineralogical, and geochemical characteristics and genesis of this economically important clay deposit have not been examined in detail previously. The present study has attempted to fill this gap. Green smectitic and cream kaolinitic claystones are abundant with smaller amounts of gray illite, dark brown Fe oxides, and silica phases occurring as stockwork/fracture infill and stain/coating. These units are covered by a dark, hard, sharp-edged, and thick silica cap. Metamorphic units exhibit cataclastic texture due to tectonic activities. Muscovite is mostly degraded to kaolinite, and feldspars show sericitization and argillization. Kaolinite typically has a platy form with irregular margins and locally sub-rounded, book-like texture suggesting hydrolysis during the hydrothermal injections. The association of Fe oxides, cristobalite/tridymite/quartz, gypsum/anhydrite, and jarosite are indicative of intense hydrothermal activities and development of kaolinite under acidic geochemical conditions. The local enrichment of SiO2, Fe2O3, S, Cu, and Au also supports this suggestion. The leaching of Sr, Rb, Ba, and Zr, and the slight increase in LREE/MREE+HREE ratios together with the negative Eu and Ce anomalies suggest the selective dissolution of muscovite, garnet, feldspar, and pyroxene by the hydrothermal fluids. Thus, abundant claystones of smectite and kaolinite were formed via the increase in Al+Fe+Mg/Si and Al±Fe/Si ratios in the alkaline and acidic environment, respectively, under the tectonic control of hydrothermal activity as seen in the alteration of chlorite, muscovite, and feldspar in metamorphic units.

中文翻译：

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土耳其 ESKİŞEHİR MİHALIÇIK 中生代变质单元内的 YARIKÇI 水热粘土矿床的起源

热液蚀变导致在安纳托利亚中西部 Mihalıççık 沿 NW-SE-和 N-S-走向断层的中生代绿泥石-、白云母-、绿泥石-白云母-片岩和石榴石-石墨千枚岩单元内开发 Yarıkçı 粘土矿床。以前没有详细研究过这个具有重要经济意义的粘土矿床的地质、矿物学和地球化学特征以及成因。本研究试图填补这一空白。绿色蒙脱石和奶油高岭土粘土富含少量灰色伊利石、深棕色氧化铁和二氧化硅相，作为网状物/裂缝填充物和染色/涂层出现。这些单元被深色、坚硬、边缘锋利且厚实的硅胶帽覆盖。由于构造活动，变质单元表现出碎裂结构。白云母大多降解为高岭石，长石显示绢云母化和泥化。高岭石通常呈片状，边缘不规则，局部呈亚圆形，书状质地，表明在热液注入过程中发生了水解。Fe 氧化物、方石英/鳞石英/石英、石膏/硬石膏和黄钾铁矾的组合表明酸性地球化学条件下高岭石的强烈热液活动和发育。SiO2、Fe2O3、S、Cu 和 Au 的局部富集也支持这一建议。Sr、Rb、Ba 和 Zr 的浸出以及 LREE/MREE+HREE 比率的轻微增加以及 Eu 和 Ce 的负异常表明白云母、石榴石、长石和辉石被热液流体选择性溶解。因此，