Trace element signatures in hematite and goethite associated with the Kiggavik–Andrew Lake structural trend U deposits (Nunavut, Canada)

Abstract

Hematite and goethite from 100 samples collected from various uranium deposits and prospects, associated alteration zones, and overlying Thelon sandstones in the Kiggavik–Andrew Lake structural trend (KALST; Nunavut, Canada) were investigated by EPMA (electron probe micro-analyzer) and LA-ICP-MS (laser ablation-inductively coupled plasma-mass spectrometer) to establish discriminant geochemical features in order to constrain indicator mineral exploration for uranium. Three groups of Fe oxides and hydroxides were identified: (1) pre-mineralization—formed during lateritic weathering mainly by replacement of previous metamorphic minerals. This group is variably enriched in P, Pb, Mo, Nb, Cu, Cr, Ni, and Co. (2) Syn-mineralization hydrothermal hematite and goethite intergrown with illite, quartz, chlorite, and calcite ± siderite constituting the typical alteration assemblage associated with the KALST U mineralization. This group can be discriminated because of its enrichment in U, Ca, Mg, Al, Si, Mn, Y, ∑REE, Zr, K, S, and Sr and depletion in P, Fe, Cr, W, Sn and Ta. The flat and un-fractionated REE patterns in this group are comparable with those reported from Kiggavik U mineralized host rocks and are most likely reflecting the signature of parental uraniferous fluids. (3) Post-mineralization hydrothermal specularite and goethite, infilling the KALST host rocks fractures and dissolution pits, are mostly depleted in Mn, Co, Y, Sr, U, and ∑REE but relatively enriched in Cr, Sn, Ta, Ge, and W. Partial least squares-discriminant analysis (PLS-DA) of the geochemical data not only differentiates among different groups of Fe oxides and hydroxides in the KALST samples but also demonstrates the evolution of trace element composition of Fe oxides and hydroxides from the basement host rocks to the mineralization. The results suggest a basement source for the U mineralization in the KALST area.