A reconnaissance study of potentially important scandium deposits associated with carbonatite and alkaline igneous complexes of the Permian Emeishan Large Igneous Province, SW China

Abstract

• The ELIP in SW China has a component of carbonatite-alkaline complexes that were not previously well known. • Pyroxenites of these complexes are composed of clinopyroxene with high Sc contents and can form low grade but high tonnage of Sc ores. • Exploration Targets for Sc in pyroxenites in three representative complexes have ∼12,000 to ∼36,000 tonnes of Sc metal at grades of ∼30 to ∼70 ppm. • Carbonatite-alkaline complexes of the ELIP may become a potentially important Sc metallogenic province and may be targets for exploration of REEs . Economically viable Sc deposits in the world are scarce and new and alternative resources are now urgently needed to ensure future sustainable supplies. We report here an essentially unknown, yet potentially important, type of Sc deposit that is associated with carbonatite and alkaline igneous complexes of the Permian Emeishan Large Igneous Province (ELIP), SW China. The ELIP is well known for its variably mineralized intrusions and flood basalts. Associated alkaline igneous complexes are minor in volume but important as possible sources of Sc and other REEs. Several such complexes occur in the N-S-trending Kangdian belt, where they are typically composed of pyroxenite, gabbro, and nepheline syenite. Some complexes also contain jacupirangite, melteigite, ijolite, and urtite. We show that some of these complexes contain carbonatites. The alkaline mafic-ultramafic rocks typically belong to either sodic or potassic magmatic series with high alkali compositions (up to 15.4 wt% Na 2 O + K 2 O). Pyroxenites in these complexes are composed of clinopyroxene with variable amounts of apatite and magnetite and have 39 to 71 ppm Sc. The Sc concentrations of these rocks may be high enough to justify mining under the current prices of Sc, which is nearly 5 times that of gold. Our preliminary study indicates a minimum of ∼12,000 to ∼36,000 tonnes of Sc metal in three representative complexes. This type of mineralization may ultimately contribute to a reliable and sustainable Sc supply chain in the future. In addition to Sc in the pyroxenites, carbonatites in these complexes will also be potentially important targets for REE exploration.