Chemical composition of black shale from four locations, greater Oslo area, Norway
Chemical analyses of main, minor and trace elements have been made of Ordovician black (alum-) shale samples collected at two different localities and one waste pile in the greater Oslo area. The study is aimed at identification of differences between black shales from different localities by using main and trace element concentrations in whole rock for "fingerprinting". The study does not attempt to interpret the element data collected in terms of geological history and genesis. The results of the chemical analysis have been converted to oxides, treated statistically and plotted in several different types of scatter and triangular/ternary diagrams, which might be used for differentiation and classification of these seemingly homogeneous shales. Variation among samples from the same locality had been investigated. When comparing results of the same element in the samples collected at one of the localities (Slemmestad) there are significant differences with respect to several of the elements analyzed. This is high-lighted in scatter diagrams. Based on different classification methods, e.g. used in classifying metamorphosed shales, the samples from each locality gather in separate clusters. Some of the plots differentiate the samples better than others, and the content of chemical elements can be recommended used in classifying shale samples from different building sites.