Mineralogy and geochemical affinities of bentonites from Kapıkaya (Eskişehir, western Turkey)

Abstract

There are numerous bentonite deposits, formed by the alteration of volcanic rocks, in the Kapıkaya area (Eskişehir, western Turkey). These deposits can be classified into three groups according to their stratigraphical levels. X-ray diffraction (XRD), scanning electron microscope (SEM), major, rare-earth and trace-element analyses of bentonites and their parent rocks from the Kapıkaya area were used to evaluate the mineralogical and geochemical properties of bentonites and their parental affinities. Mineral assemblages resulting from bentonite deposits consist mostly of clay minerals, gypsum, cristobalite/opal-CT, quartz, feldspar, calcite and dolomite. The clay minerals are represented mainly by dioctahedral smectite and lesser amounts of illite and chlorite. The enrichment and depletion of the elements indicates open-system alteration conditions. The enrichments in MgO, Fe2O3, TiO2, Co, Pb, Zn, and Ni are related to the precipitation of hydrothermal solutions channelled throughout ultramafic sources. The main differences in mineralogy and geochemistry of bentonites from the Kapıkaya area are in the smectite composition and the contents of major, rare-earth and other trace elements. The data obtained show that the types of parent rock the influenced the mineralogical and geochemical compositions of the bentonites.

Mineralogical and geochemical characteristics of K‐bentonites from the Late Ordovician to the Early Silurian in South China and their geological significance

“…K‐bentonites in the Ordovician–Silurian times are globally present in North America, South America, Northern and Central Europe, and Asia (China; Huff, ; Huff, Bergström, & Kolata, ), especially the Lower–Middle Ordovician Famatinian Bentonite of Argentina (Astini, Collo, & Martina, ; Fanning et al, ; Huff, Davis, Bergström, Krekeler, et al, ), and the Upper Ordovician Deicke–Millbrig–Kinnekulle Bentonite suite of North America and Sweden (Bergström, Huff, Kolata, & Bauert, ; Bergström, Huff, Saltzman, Kolata, & Leslie, ; Huff, Bergström, & Kolata, ; Kolata, Huff, & Bergström, ). There is a long global history of study of K‐bentonites, which yielded important results in chronostratigraphy, paleo‐continental reconstruction, tectonic setting, and stratigraphic correlations (Astini et al, ; Bergström, Huff, & Kolata, ; Bergström, Huff, Kolata, & Melchin, ; Caligari, Abedini, & Fatahi, ; Huff, ; Huff et al, ; Huff, Anderson, Rundle, & Odin, ; Huff, Bergström, & Kolata, ; Huff, Bergström, Kolata, & Sun, ; Huff, Davis, & Bergström, ; Bergström, Huff, Kolata, & Bauert, ; Huff, Merriman, Morgan, & Roberts, ; Kiipli, Dahlqvist, Kallaste, Kiipli, & Nolvak, ; Kolata, Frost, & Huff, ; Min, Renne, & Huff, ; Mitchell, Adhya, Bergström, Joy, & Delano, ; Ricardo, Collo, & Martina, ; Tucker et al, ; Yildiz & Dumlupunar, ). Nevertheless, the Chinese scholars have limited research experience of Ordovician bentonites.…”