Summary of knowledge about Norwegian anorthosite prospecting - in relation to Greenland anorthosites

NGU Rapport 2010.020

This report gives an overview of Norwegian prospecting on anorthosites, with emphasis on the calcic types dominant in the Inner Sogn-Voss area of Western Norway. The high aluminium content of these large anorthosite bodies by the Sognefjord has made them the target of potential alternative sources for the aluminium-industry. In several phases during the last 90 years major Norwegian companies have done extensive geological investigations with this aim. The Sogn anorthosites contain a plagioclase with labradorite-bytownite composition, in the dominating range of 60-78% anorthite.

Many large Greenland anorthosites (An60-90) prove to be somewhat higher in both acid solubility and aluminium content, thus giving them a favour to the Norwegian ones.

The large anorthosites in Rogaland (SW Norway) have lower aluminium content and are thus not interesting as an aluminium raw material. The titanium-rich ilmenite bodies and some alternative uses for this andesine-labradorite anorthosite (An40-55) are thus covered in less detail.

Field relationships with regard to mineralogical and processing considerations are presented and some of the relevant process alternatives and the scope of potential end uses are given.