New geochemical data from a collection of till samples from Nordland, Troms and Finnmark

Abstract

For the whole area covered by the MINN project there exist collections of mineral soil (till) samples that were originally collected during the early to mid 1980s at an average density of 1 site\/50 km2 for the Nordkalott and Nordland-Troms projects. These samples were stored at NGU for 25-30 years. It was decided that it would be justified to retrieve remaining material from the sample store and test what kind of results can be found when re-analysing these samples using modern techniques. It was possible to retrieve 1144 small samples from Finnmark that were already sieved to <0.063 mm. For Nordland-Troms sieved material was no longer available. However, 979 original and untouched samples weighing 2-7 kg each could be retrieved from the NGU sample store. It was considered too time consuming to sieve these samples to <0.063 mm. In addition, several projects during the last 15 years had, with advantage, used the <2 mm fraction. It was thus decided to sieve these samples to <2 mm prior to the analysis. When preparing all the samples for analysis they were randomised and standard samples and sample duplicates were introduced at a rate of one in twenty for quality control (QC) purposes. Based on previous good experience, analyses were carried out in a commercial laboratory in Canada (ACME) using an aqua regia extraction. For the Finnmark samples 7.5 g of sample were used for the extraction, for the coarser Nordland-Troms samples 15 g of sample were used for the extraction. The extracts were finished on a combination of ICP-MS and ICP-AES and concentrations for 65 elements were reported.