Clay mineral association in the salt formation of the Transylvanian Basin and its paleoenvironmental significance

The investigated clay fraction was separated from salt samples recovered from three boreholes located in the Praid salt deposit area. For comparison, samples collected from Turda deposit (Franz Josef adit, the Rudolf and Ghizele chambers) and from the salt massif from Sărăţel were also analyzed. The qualitative investigations evidenced a clay minerals association dominated by illite and chlorite accompanied by subordinate amounts of kaolinite, smectite, fibrous clays (sepiolite, palygorskite), and in minor amounts, by 14/14 chlorite/vermiculite and chlorite/smectite interstratifications. A quantitative evaluation (%) including a standard graphical representation was performed only for the borehole samples (Praid), according to the vertical distribution. The genetical interpretation of the identified clay minerals association took into account the influence of the sedimentation mechanisms and the climate control on the mineral phases. The environment of formation for the salt in the Transylvanian Basin was defined by the presence of specific climatic factors, also suggested by the palynological investigations