A study of major element and Rb, Sr geochemistry as well as clay mineralogy in argillites from the dolerite-intruded, Late Proterozoic fluviatile Almesåkra group of Sweden is reported. The contents and proportions of the alkalis in the potassic, mainly non-calcareous argillites are determined largely by the composition of the associated feldspathic sandstones. The basic intrusions influenced the oxidation level in the red argillites with reduction of hematite in greyish to blackish contact rocks. In red argillites, least influenced by the intrusions, the clay mineralogy is virtually illitic and the illite crystallinity indicates a deep-diagenetic to diagenetic degree of metamorphism. Chlorites, like illite crystallinity, are best developed in argillites closest to the intrusions. The Sr-level in contact argillites is much higher than in other Precambrian shales. It is significantly lower in the red argillites. The difference in Sr-contents is suggested to be due mainly to a transfer of Sr from the melts which were comparatively high in this element.