POTENTIAL PHOSPHATE ROCK RESOURCES IN NORWAY
NGU FOCUS 01.02.2023 / WRITTEN BY P. IHLEN & A. RAANESS
A large variety of phosphate-rock deposits and occurrences are found in Norway (http://dx.doi org/10.1016/j. oregeorev. 2013.11.003, 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 fuor-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 anorthositemangerite-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.
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 fgure). As shown in the fgure 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 OIP include clinoand 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. It comprises massive ores with modes in the range 10-24 % apatite, 5-15 % ilmenite, 25-60 % titaniferous magnetite and 25-50 % mafc silicates. Kodal Minerals Ltd has calculated indicated + inferred ore reserves to 49 Mt with about 12 wt.% apatite (http://www. kodalminerals.com) which contains ca. 1 wt. % REO. The deposit is comparable to many P-Fe-Ti-rich ores found widespread in mangerites of the Paleoproterozoic AMCG-province in Lofoten-Vesterålen in northern Norway (LVMC; Coint et al., 2020).
References: https://www.frame.lneg.pt/wp-content/uploads/2022/03/FRAME_WP4 deliverable-D.4.3.pdf https://geoera.eu/projects/mintell4eu7/
Coint, N. , J. K. Keiding and Ihlen, P. M. (2020). “Evidence for Silicate–Liquid Immiscibility in Monzonites and Petrogenesis of Associated Fe–Ti–P-rich rocks: Example from the Raftsund Intrusion, Lofoten, Northern Norway.” Journal of Petrology 61(4).
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-VestfoldTelemark – Nolwenn Coint and Eduardo Mansur
