Origin and diagenetic evolution of sepiolite-palygorskite formations in Turkey

Sepiolite-palygorskite occurrences in Eskişehir-Sarısu, Konya-Yunak, Sivrihisar-İlyaspaşa, Sivas-Çetinkaya and Malatya-Hekimhan regions which have different formation environments and conditions from each other were investigated.Sepiolite-palygorskite and related minerals and groundwaters were evaluated by equilibrium activity diagrams in the system of MgO-Al2O3-SiO2-CaO-H2O-CO2-HCl with respect to log (aMg2+/a2H+) versus log (aH4SiO4) at various log (aAl3+/a3H+) values. The most important variables effecting the formations of sepiolite and palygorskite are pH (alkalinity) of the environment, aluminum activity, silica activity and type of the carbonate. Especially, aluminum activity determines the mineral assemblages.According to the oxygen and hydrogen isotope results of the sepiolite, palygorskite and groundwater samples, the waters in the regions are meteoric in origin and in equilibrium with those minerals. 18O ve 13C isotope values of carbonate minerals found in the paragenesis give valuable informations to determine the formation environments and cilimates in the regions.