FOCUS NGU FOCUS NR.2 FEB 2023
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W W W E VISIT FOR M .NGU.NO O RE I N FO
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 %