ReviewCharacterization of apatite resources in Norway and their REE potential - A review

- Igneous phosphate rocks are the most promising target for apatite exploration in Norway.
- Apatite-Fe-Ti deposits in complexes of monzonites and massif-type anorthosites are particularly promising.
- The most important apatite resource is the Bjerkreim-Sokndal Layered Intrusion of the Rogaland Anorthosite Province.
- High-REE apatite is mainly confined to pyroxenite bodies in monzonitic plutons (e.g. the Kodal deposit).

Apatite is a necessity for the production of phosphorus fertilizers and presents a potential raw material for the extraction of REE and Y. A wide spectrum of apatite deposits is found in Norway including sedimentary, igneous, and vein type deposits. The igneous deposits which appear to have the greatest potential for exploitation occur associated with alkaline complexes, massif-type anorthosite complexes and monzonitic complexes. One of the most promising is found in the monzonoritic Bjerkreim-Sokndal Layered Intrusion of the early Neoproterozoic Rogaland Anorthosite Province in southwest Norway. The intrusion hosts three cumulate units with high-grade ore zones. The most promising resource is confined to MCU IV which is 50-170 m thick and nearly 10 km long with average normative contents of 10.2% apatite, 12.4% ilmenite and 7.3% vanadium-rich magnetite. The late Neoproterozoic-Cambrian carbonatite-bearing alkaline complexes are generally of low grade to represent potential resources of apatite as the sole commodity. However, apatite may represent a byproduct of potential Nb and REE + Y mineralisation in the Fen Complex in southern Norway. The late Ordovician-Silurian Misværdal complex comprising multiple alkali clinopyroxenite intrusions in the Uppermost Allochthon of the Caledonides in northern Norway contains 1-1.5 km long and 100-200 m wide ultrapotassic clinopyroxenite dykes with average contents of 7-10 wt.% apatite and with intermediate levels of TREY (~ 0.5 wt.%). However, high levels of Th in the apatite make it less suitable as a raw material for fertilizer production. Apatite-Fe-Ti oxide ores being characteristic for the monzonitic complexes are especially well developed in the Permian Oslo Igneous Province where apatite-rich magnetite clinopyroxenite cumulates are found in the Larvik Plutonic Complex. The Kodal body has an inferred open-pit ore reserve calculated to 70 Mt with approximately 11.6 wt.% apatite, 3.0 wt.% ilmenite and 26.5 wt.% ilmenomagnetite. The apatite contains about 1 wt.% REE. Comparable types of deposits of Palaeoproterozoic age have recently been recognized in the alkali-calcic mangeritic to syenitic intrusions in the Lofoten-Vesterålen Mangerite Complex in northern Norway, whereas complexes with variable proportions of anorthosites (s.s.), jotunites and mangerites occurring in the Middle Allochthon of the Caledonides in South Norway also are known to host apatite-bearing Fe-Ti oxide deposits, some high in apatite. These complexes represent potential areas for green-field exploration. The TREY (TREE + Y) contents of the apatite in the igneous deposits are discussed and comprise very low levels in the Bjerkreim-Sokndal Layered Intrusion, intermediate levels in the carbonatites and pyroxenites of the alkaline complexes as well as nelsonite dykes and mangerite-associated deposits to high levels in the monzonite-associated deposits.