TY - JOUR
T1 - Scandium speciation in a world-class lateritic deposit
AU - Chasse, Mathieu
AU - Griffin, William
AU - O'Reilly, Suzanne Y
AU - Calas, Georges
PY - 2017
Y1 - 2017
N2 - Scandium (Sc) has unique properties, highly valued for many applications. Future supply is expected to rely on unusually high-grade (up to 1000 ppm) lateritic Sc ores discovered in Eastern Australia. To understand the origin of such exceptional concentrations, we investigated Sc speciation in one of these deposits. The major factors are unusually high concentrations in the parent rock together with lateritic weathering over long time scales in a stable tectonic context. At microscopic and atomic scales, by combining X-ray absorption near-edge structure spectroscopy, X-ray diffraction and microscopic and chemical analyses, we show that Sc-rich volumes are associated with iron oxides. In particular, Sc adsorbed on goethite accounts for ca. 80 % of the Sc budget in our samples. The remaining Sc is incorporated in the crystal structure of haematite, substituting for Fe3+. Scandium grades reflect the high capacity of goethite to adsorb this element. In contrast, the influence of haematite is limited by the low levels of Sc that its structure can incorporate. These crystal-chemical controls play a major role in lateritic Sc deposits developed over ultramafic–mafic rocks.
AB - Scandium (Sc) has unique properties, highly valued for many applications. Future supply is expected to rely on unusually high-grade (up to 1000 ppm) lateritic Sc ores discovered in Eastern Australia. To understand the origin of such exceptional concentrations, we investigated Sc speciation in one of these deposits. The major factors are unusually high concentrations in the parent rock together with lateritic weathering over long time scales in a stable tectonic context. At microscopic and atomic scales, by combining X-ray absorption near-edge structure spectroscopy, X-ray diffraction and microscopic and chemical analyses, we show that Sc-rich volumes are associated with iron oxides. In particular, Sc adsorbed on goethite accounts for ca. 80 % of the Sc budget in our samples. The remaining Sc is incorporated in the crystal structure of haematite, substituting for Fe3+. Scandium grades reflect the high capacity of goethite to adsorb this element. In contrast, the influence of haematite is limited by the low levels of Sc that its structure can incorporate. These crystal-chemical controls play a major role in lateritic Sc deposits developed over ultramafic–mafic rocks.
UR - http://www.scopus.com/inward/record.url?scp=85037029463&partnerID=8YFLogxK
U2 - 10.7185/geochemlet.1711
DO - 10.7185/geochemlet.1711
M3 - Article
SN - 2410-3403
VL - 3
SP - 105
EP - 114
JO - Geochemical Perspectives Letters
JF - Geochemical Perspectives Letters
IS - 2
ER -