Mineralogical and geochemical studies of lower palaeozoic rocks from the Trondheim and Oslo regions, Norway

84 samples of Lower Palaeozoic sediments and volcanics were analysed geochemically and mineralogically. In the eugeosynclinal sections in the SW Trondheim Region the composition of the sediments reflects local erosion of volcanic rocks. Sediments derived from basic, tholeiitic volcanic rocks in this part of the Trondheim Region are enriched in the minerals chlorite, albite, and trace elements Se, Co, and V. While the Trondheim Region sediments show geochemical variations characteristic of immature, fast deposited sediments, those from the Oslo Region seem to reflect conditions where slow sedimentation of finegrained material predominated. High concentrations of chlorite, Se, and Co in the epicontinental sediments of Middle Ordovician age from the Oslo Region indicate enrichments of basic volcanic debris in these beds.