Petrography and geochemistry of granitoids from the Samphire Pluton, South Australia: implications for uranium mineralisation in overlying sediments

摘要: Abstract The Blackbush uranium deposit (JORC Inferred Resource: 12,580 tonnes U), located on the north-eastern Eyre Peninsula, is currently only sediment-hosted U investigated in detail Gawler Craton. Uranium hosted within Eocene sandstone of Kanaka Beds, overlying Mesoproterozoic granites Samphire pluton, affiliated with Hiltaba Intrusive Suite (~ 1.6 Ga). These are considered most probable source rocks for mineralisation. By constraining petrography and mineralogy granites, insights into post-emplacement evolution can be gained, which may provide an exploration indicator other systems. Three geochemically distinct granite types were identified Pluton correspond to domains interpreted from geophysical data. All show complex alteration overprints textures increasing intensity closer deposit, as well crosscutting veining. Alkali feldspar has been replaced by porous K-feldspar albite, plagioclase overprinted assemblage albite + sericite ± calc-silicates (prehnite, pumpellyite epidote). This style regionally widespread known Hiltaba-aged associated iron-oxide copper‑gold mineralisation at Olympic Dam Moonta-Wallaroo region. In two biotite calcic garnet. Calc-silicates indicative Ca-metasomatism, sourced anorthite component altered plagioclase. Minor clay feldspars present all samples. Mineral assemblages veins include quartz + hematite, hematite + coffinite, fluorite + quartz, minerals. chlorite sericite found vein types. anomalously rich (concentrations between 10 81 ppm). Highly variable Th/U ratios, hydrothermal minerals (mostly coffinite) veins, clear evidence mobility. have preconcentrated upper parts was subsequently leached after deposition sediment.