3D representation of geochemical data, the corresponding alteration and associated REE mobility at the Ranger uranium deposit, Northern Territory, Australia |
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| Authors: | Louise A Fisher James S Cleverley Mark Pownceby Colin MacRae |
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| Institution: | 1. CSIRO Earth Science and Engineering, Minerals Down Under Flagship, ARRC, PO Box 1130, Bentley, Perth, WA, 6102, Australia
2. CSIRO Process Science and Engineering, Minerals Down Under Flagship, Box 312, Clayton South, Melbourne, VIC, 3169, Australia
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| Abstract: | Interrogation and 3D visualisation of multiple multi-element data sets collected at the Ranger 1 No. 3 uranium mine, in the Northern Territory of Australia, show a distinct and large-scale chemical zonation around the ore body. A central zone of Mg alteration, dominated by extensive clinochlore alteration, overprints a biotite–muscovite–K-feldspar assemblage which shows increasing loss of Na, Ba and Ca moving towards the ore body. Manipulation of pre-existing geochemical data and integration of new data collected from targeted ‘niche’ samples make it possible to recognise chemical architecture within the system and identify potential fluid conduits. New trace element and rare earth element (REE) data show strong fractionation associated with the zoned alteration around the deposit and with fault planes that intersect and bound the deposit. Within the most altered portion of the system, isocon analysis indicates addition of elements including Mg, S, Cu, Au and Ni and removal of elements including Ca, K, Ba and Na within a zone of damage associated with ore precipitation. In the more distal parts of the system, processes of alteration and replacement associated with the mineralising system can be recognised. REE element data show enrichment in HREE centred about a characteristic peak in Dy in the high-grade ore zone while LREEs are enriched in the outermost portions of the system. The patterns recognised in 3D in zoning of geochemical groups and contoured S, K and Mg abundance and the observed REE patterns suggest a fluid flow regime in which fluids were predominately migrating upwards during ore deposition within the core of the ore system. |
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