Age and paragenesis of mineralisation at Coronation Hill uranium deposit, Northern Territory, Australia

• Published in: Mineralium Deposita
• Main Authors: Orth, K, Meffre, S, Davidson, G
• Format: Article in Journal/Newspaper
• Language: English
• Published: Springer-Verlag 2014
• Subjects: Earth Sciences; Geochemistry; Isotope Geochemistry; Canada; McArthur; Sav’; Athabascan
• Online Access: https://doi.org/10.1007/s00126-013-0501-4; http://ecite.utas.edu.au/98097

Coronation Hill is a U + Au + platinum group elements deposit in the South Alligator Valley (SAV) field in northern Australia, south of the better known unconformity-style U East Alligator Rivers (EAR) field. The SAV field differs from the EAR by having a more complex basin-basement architecture. A volcanically active fault trough (Jawoyn Sub-basin) developed on older basement and then was disrupted by renewed faulting, before being buried beneath regional McArthur Basin sandstones that are also the main hanging wall to the EAR deposits. Primary mineralisation at Coronation Hill formed at 1607 26 Ma (rather than 600900 Ma as previously thought), and so it is likely that the SAV was part of a single west McArthur Basin dilational event. Most ore is hosted in sub-vertical faults and breccias in the competent volcanic cover sequence. This favoured fluid mixing, acid buffering (forming illite) and oxidation of Fe 2+ and reduced C-rich assemblages as important uranium depositional mechanisms. However, reduction of U in fractured older pyrite (Pb model age of 1833 67 Ma) is an important trap in diorite. Some primary ore was remobilised at 675 21 Ma to form coarse uraninite + Ni-Co pyrite networks containing radiogenic Pb. Coronation Hill is polymetallic, and in this respect resembles the egress-style U deposits in the Athabascan Basin (Canada). However, these are all cover-hosted. A hypothesis for further testing is that Coronation Hill is also egress-style, with ores formed by fluids rising through basement-hosted fault networks (U reduction by diorite pyrite and carbonaceous shale), and into veins and breccias in the overlying Jawoyn Sub-basin volcano-sedimentary succession.