| Abstract (english) | This study investigates lithological, mineralogical and chemical influence on element content in overbank sediments.The advantages of investigated area (Žumberak and Samoborsko gorje) for performing such study are the following: (1) expansive drainage system and (2) two distinctly different lithologies, such as carbonate and non-carbonate sedimentary rocks, associated in a complex way. The analysis of 36 elements has been carried out in <125ì m fraction of 42 selected samples using multi-acid digestion, followed by ICP-IES determination.Hg has been analyzed by flameless AAS.The mineral composition of the same fraction has been determinated by means of semiquantitative X-ray diffraction analysis (XRD). The relationships between geochemistry, mineralogy and lithology were investigated using canonical correlation analysis.The lithological set consisted of five variables: (1) clastites of Permian and lower Triassic age (P-T1 ) ; (2)Triassic dolomites (T2, 3 ) ; (3) Jurassic limestones (J) ; (4) siliciclastic-lime flysch like complex (K2 -Pc) and (5 clastites of Neogene age (M-Pl).The mineralogical set of variables included also five variables:(1)phyllosilicates ; (2)feldspars ; (3)calcite ; (4)dolomite ; and (5)Fe-oxihydro- xides (presented by concentrations of dithionite-citrate-bicarbonate extracted Fe). The geochemical set has been divided in two subsets.The main elements subset involved Fe, Ca, Mg, Ti, Al, Na, and K. The subordinate and trace elements subset encompassed Cu, Pb, Zn, Ni, Co, Mn, As, Sr, V, P, La, Ba and Hg. The values that excessively deviated from the mean value have been discarded.The extreme values of Cu (662 mg/kg), Pb (110), Ba (3928 mg/kg)and Hg (11650 ì g/kg) in the overbank sample from Rudarska Gradna catchment were the consequence of sulphide-barite mineralisation.The extreme concentrations of Zn (177 mg/kg) and Pb (102 mg/kg)in Ludvić catchment indicated sulphide mineralisation. The relationship between lithology and mineralogy is explained by only one but high (0.81) and significant canonical correlation, dominated by the following variables in the two canonical eigenvectors: T2, 3 and J and dolomite negatively associated with M-Pl and phyllosilicates. Lithological one (0.92) is a result of strong relationship between Permian and lower Triassic clastites and iron, probably as a consequence of Permian iron mineralisation.The second canonical correlation is 0.82 dominated by the structural coefficients of calcium.The relationship between lithology and minor and trace elements is confirmed by two the structural coefficients of P-T1 clastics, K2 -Pc clastics and Zn, Co, Mn, Ni, As, Cu and Pb. It has been assumed that mineral contents are the results of mixing of rock units weathering products from bulk drainage area.The dominance of carbonates, specially dolomites covering 50% of investigated area can be inferred. The results from this survey demonstrate that background abundance for many elements are affected by variations in catchment area and could be used as baseline values.It is concluded that overbank sediment in investigated area is a good sampling medium for regional geochemical mapping and environmental studies. |
