A large variety of phosphate-rock deposits and occurrences are found in Norway and references therein. They include sedimentary, igneous and hydrothermal deposits. The former comprises low-grade phosphorite accumulations in Late Neoproterozoic to Early Paleozoic shale-siltstone sequences along the eastern margin of the Caledonides.
The other types of phosphate rocks are composed of crystalline apatite, i.e. mainly fluor-apatite in igneous deposits, and chlorine-rich apatite in hydrothermal veins. Igneous deposits which appear to have the greatest potential for exploitation in the future, occur in association with anorthosite mangerite charnockite-granite (AMCG) complexes, where apatite is associated with high concentrations of Fe-Ti oxides, and in carbonatite alkaline complexes, which in contrast are poor in Fe-Ti oxides.
Most promising phosphate resource in Norway
Presently, the most promising phosphate rock resource in Norway is found in the noritic Bjerkreim-Sokndal Layered Intrusion (BKSK) in the AMCG complex of Rogaland (RAP). It is composed of six megacyclic cumulate units (MCU) situated in an open synformal structure. Each unit comprises one or more members with bulk compositions ranging from anorthosite (A) via troctolite (B) and norite (C) to gabbronorite (E, F) in the upper part, where high-grade Fe-Ti-P ore zones are developed. These include the ore zones in the MCU IB-E, III-E and IV-E (see figure).
As shown in the figure the ore zones contain a total of 26-34 % value minerals, i.e. apatite (ap), ilmenite (ilm) and vanadium-rich magnetite (Vmt). The BKSK was mapped and sampled in the late 1990’s and early 2000’s by NGU, partly in cooperation with Norsk Hydro (Yara.)
Recent follow-up studies and extensive drilling by Norge Mining plc in part of the deposit show that there is a total indicated and inferred mineral resource of 1.55 billion tonnes at close to the western end of Lake Tekse.
The sub-alkaline and alkaline igneous rocks of the Permian Oslo rift include clino and orthopyroxene-bearing monzonitic intrusions which host dyke-like bodies and pods of Fe-Ti-P-rich rocks. The Kodal deposit is the largest of this type and contains 10-24 % apatite, 5-15 % ilmenite, 25-60 % titaniferous magnetite and 25-50 % mafic silicates. Kodal Minerals Ltd has calculated indicated + inferred ore reserves to 49 Mt with about 12 wt.% apatite which contains ca. 1 wt. % REO.
Preliminary analyses of the calcite-carbonatite from the Fen alkaline and carbonatite complex highlight the phosphorus resource potential of the complex, although no resource estimate is available. This is consistent with the existing grade of 3.05 and 3.29 wt% for the two bodies previously mined for niobium (Björlykke, 1952).
References
Mineral Intelligence for Europe (Mintell4EU).
Björlykke, H., (1952). Rapport over niobforekomstene på Söve ved Ulefoss, 67p.
Decrée, S., N. Coint, V. Debaille, G. Hagen-Peter, T. Leduc and H. Schiellerup (2023). “The potential for REEs in igneous-related apatite deposits in Europe.” Geological Society, London, Special Publications 526(1): SP526-2021-2175.
Ihlen, P. M., Schiellerup, H., Gautneb, H., and Skår, Ø., 2014. Characterization of apatite resources in Norway and their REE potential — A review. Ore Geology Reviews, 58: 126–147.
Ongoing projects at NGU
Formation of phosphate deposits in Norway- Nolwenn Coint and Eduardo Mansur
Critical metals (P-REE) potential in the southern part of the Oslo rift-Vestfold Telemark – Nolwenn Coint and Eduardo Mansur.
