Mineralogia i geochemia iłów poznanskich z wybranych złóż Wielkopolski

The deposits under study (Brzostów, Krotoszyn, Ostrzeszów, Góra) and the Leszno borehole are located in Southern Wielkopolska, Polish Lowlands. Geochemical characteristics of the upper part of the Neogene Poznan Formation were presented on the basis of major elements analyses. The sediments were classified as clays, silts and sands. Quartz in coarse fraction and clay minerals (smectite, mixed layers smectite/illite, kaolinite, traces of chlorite and halloysite) in fine fraction are the main components. Their chemical composition depends mainly on mineralogical content. The sediments were strongly depleted in Ca and Na during weathering processes. Calculated chemical indices of alternation, CIA and CIW range from 59.9 to 91 and 68 to 93 respectively, indicating intense chemical weathering phenomena.