Geochemistry of drill cores from the Nussir copper deposit, Kvalsund, Finnmark, Northern Norway

Abstract

The study is based on over 1000 analysed drill core samples, drilled before 2007, from the Nussir copper deposit in Kvalsund in Finnmark, Northern Norway. The scope of the study was to find any correlations among the metals and eventually any metal zonations.\rSeveral conclusions can be drawn from the study of chemical composition of the drill cores. However, some of them are indicative and should be confrimed by further analyses, re-logging of the drill cores and mineralogical studies.\rAnalyses of acid-soluble digestions show the metal distributions as well as give indications of lithologies present. There is, to a varying degree, a positive correlation between Cu and Ag, S, As, Co, Au and Fe. The enrichments of other transitions metals than Cu are limited.\rHigh Cu-values are found both within and in the footwall of the assumed \"ore dolomite\" zone. Actually, the highest Cu-values commonly occur in the footwall of the dolomite. The ore dolomite is best defined in the western part of the deposit, and the Cu-mineralisations occur in less dolomitic rocks in the eastern part. The core length of the Cu-mineralised zone is, in several sections, several meters, up to 8-9 m when the cut-off is taken as 0.25% Cu.\rThe relationship between Cu, Fe and S can be used to give indications on both lateral and vertical zonation of different copper minerals. The highest proportions of the Cu-rich sulphides, bornite and chalcocite\/digenite, occur in the westernmost and in the eastern parts of the deposit. The highest Ag values are found in chalcopyrite-rich samples in the folded part of the deposit. Further studies are needed to verify whether this zonation and Ag distribution are a primary feature or due to later remobilisation.\rThe host rocks of the two Cu-mineralised zones in the westernmost part of the area have different chemical composition. The chemical characteristics of the lower Cu-zone, which includes enrichment of Pt, are only found in drill hole Bh 60.