Saponite from the Emet colemanite mines, Kutahya, Turkey

Clay mineralogy and whole-rock chemistry of the berate-bearing layers of th e Hisarclk and Esbey mines were examined. The Hisarclk clays occur as lamin ated or unlaminated clay layers with sharp contacts. Unlaminated layers con tain quartz derived from metamorphic rocks and carbonate fragments in a cla y matrix, and are interpreted as reworked tuffs deposited in playa-lake env ironments. An important feature is that the unlaminated clays contain littl e MgO (3-15 wt. %) as compared with the laminated clays (15-30 wt. %). As p revious studies have shown, the clay fraction of the studied profile contai ns predominantly Li-bearing saponite, and accounts for 60-90 wt. % of the c lay fraction (<2 mu m). Illite in the clay fraction varies from 0 to 67 wt. % and the average illite percentage never exceeds 40 wt. %. Chlorite is sc arce (2-5 wt. %). Illite-smectite interstratified clays (illite at 70%, sme ctite at 30%) were only found in low concentrations in the laminated clay l ayers of the upper limestone unit (above the berate zone), where illite-2M of detrital origin is also present. The Esbey clays occur interstratified w ith colemanite layers and envelope colemanite nodules. Calcite is the major mineral of the clays whereas quartz, plagioclase, feldspar. colemanite, an d cahnite are minor components. The MgO contents vary between 4.70-13.95 wt . % in the clays interstratified with colemanite layers, between 7.24-11.89 wt. % in the enveloping clays, and between 10.27-21.25 wt. % in clays loca ted above the colemanite zone. The composition of the clay fraction (< 2 mu m) in all samples is similar. Smectite represents between 40-90 wt. % of t he clay fraction in the upper portion of the stratigraphic profile and decr eases towards the lower part of the stratigraphic profile. Smectite always occurs with illite which may vary from 20 to 90 wt. % of the clay fraction, and a small amount of kaolinite and chlorite. Ilite-2M polytype is abundan t. The d(060)-reflection position suggests that the smectite minerals from the Hisarclk and Esbey colemanite mines contain both dioctahedral and trioc tahedral smectites to form a transitional zone. These smectites are a produ ct of a magnesium-rich alkaline playa-lake environment.