PCA of Fe-oxides MLA data as an advanced tool in provenance discrimination and indicator mineral exploration : case study from bedrock and till from the Kiggavik U deposits area (Nunavut, Canada)

• Published in: Journal of Geochemical Exploration
• Main Authors: Makvandi, Sheida, Beaudoin, Georges, McClenaghan, Margaret Beth, Quirt, D., Ledru, Patrick
• Format: Other/Unknown Material
• Language: English
• Published: Association of Exploration Geochemists 2019
• Subjects: Fe-oxide; Kiggavik; Till; MLA; PCA; Grain size; Mineral association; Oxydes de fer; Uranium; Minerais > Échantillonnage et estimation; Drift (Glaciologie); Nunavut; Canada
• Online Access: https://hdl.handle.net/20.500.11794/34314; https://doi.org/10.1016/j.gexplo.2018.11.013

Magnetite and hematite grains from the 0.25–0.5 mm and 0.5–2.0 mm ferromagnetic fractions of ten till samples collected up-ice, overlying and down-ice of the Kiggavik U deposits (Nunavut, Canada), as well as eight bedrock samples from Kiggavik igneous and metasedimentary basement and overlying sedimentary rocks were characterized for their grain size and mineral association using optical microscopy, scanning electron microscopy (SEM) and mineral liberation analysis (MLA). Principal component analysis (PCA) was used to evaluate the MLA data for Fe-oxide mineral association and grain size distribution. PCA shows that mineralogical and granulometric differences in Fe-oxides from Kiggavik igneous rocks distinguish them from that of Kiggavik metasedimentary and sedimentary rocks. In addition, The PCA results indicate that the composition and abundance of minerals associated/intergrown with Fe-oxides are not only different in various till samples, but also in different size fractions of the same sample. Higher proportions of hornblende, quartz, gahnite, grunerite, apatite, chromite and sulfides are intergrown with Fe-oxides in the 0.5–2.0 mm till fraction, as compared to the 0.25–0.5 mm fraction in which Fe-oxides are mostly associated with pyroxene, titanite, rutile, feldspars, calcite and zircon. The mineral associations and grain sizes of proximal bedrocks are reflected in smaller size fractions of Kiggavik till, whereas detrital grains in the 0.5–2.0 mm fraction of Kiggavik till may have originated from distal sources. PCA also shows that Fe-oxides from the Kiggavik bedrock and till can be discriminated from those of volcanogenic massive sulfide (VMS) deposits because of smaller grain sizes and higher abundances of sulfides, gahnite, axinite, corundum, hypersthene and pyroxene intergrown with VMS Fe-oxides. This study emphasizes the importance of selecting suitable representative grain size fractions of till, or other sediments, when using indicator minerals for exploration. The results of PCA of Fe-oxides MLA ...