Metal and mineral distribution in the Bleikvassli Zn-Pb deposit, Nordland, Norway

Studies of metal zonations in the Bleikvassli deposit are important, both for detailed planning of a drilling program and for subsequent interpretations of the results. For this investigation, drillhole data were selected from profiles throughout the deposits at intervals of about 100 meters, except for the old, southern part of the deposit, where all profiles where used because of scarcity of data. The total number of drillcore intersections analysed is 461 and is composed of 1437 individual analyses, representing 1953 meters of drillcore. The data has been weighted according to the lengths of the analyzed intervals and average of each ore intersection have been calculated. This study show the presence of a pronounced metal zonation in the deposit, with enrichment of copper in the deeper, central part of the deposit, whereas zinc and lead are relatively enriched towards the upper and more northern part of the deposit. This zonation accords with a mineralogical zonation: pyrrhotite ore contains chlorite and/or biotite is relatively enriched in copper; pyrite ore contains muscovite and/or biotite, and is relatively enriched in zinc and lead. A strong correlation between zinc and lead shows that no major redistribution and separation of these metals took place during the tectonic events affecting the deposit, and that the large-scale zonation observed are likely to be of primary origin. Silver and lead are highly correlated, support- ing the view of galena as the main silver carrier in the deposit. Manganese, and to some extent barium, are associated with the copperrich part of the deposit. This could be a coincidence, due to a primary enrichment in the sediments. Referring to idealized models for SEDEX type deposits, the pyrrhotite-ore enriched in copper could represent the proximal part of the deposit and the pyrite-ore enriched in zinc would be the more distal part. A

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Tilgjengelig:
NGU-biblioteket
Serier:
NGU-rapport
Serienr:
98.064
Page number:
52
ISSN:
0800-3416
Dokumenttype:
Rapport
Fylke:
Nordland