Mary Kathleen metamorphic-hydrothermal uranium-rare-earth element deposit: Ore genesis and numerical model of coupled deformation and fluid flow

Oliver, N. H., Pearson, P. J., Holcombe, R. J. and Ord, A. (1999) Mary Kathleen metamorphic-hydrothermal uranium-rare-earth element deposit: Ore genesis and numerical model of coupled deformation and fluid flow. Australian Journal of Earth Sciences, 46 3: 467-484. doi:10.1046/j.1440-0952.1999.00718.x


Author Oliver, N. H.
Pearson, P. J.
Holcombe, R. J.
Ord, A.
Title Mary Kathleen metamorphic-hydrothermal uranium-rare-earth element deposit: Ore genesis and numerical model of coupled deformation and fluid flow
Journal name Australian Journal of Earth Sciences   Check publisher's open access policy
ISSN 0812-0099
1440-0952
Publication date 1999-06
Sub-type Article (original research)
DOI 10.1046/j.1440-0952.1999.00718.x
Volume 46
Issue 3
Start page 467
End page 484
Total pages 18
Editor A. E. Cockbain
Place of publication Melbourne, VIC, A
Publisher Taylor & Francis
Collection year 1999
Language eng
Subject C1
260106 Ore Deposit Petrology
780104 Earth sciences
Formatted abstract
The Mary Kathleen U–REE orebody of the Proterozoic Mt Isa Block was the product of chemical and physical interaction between regional metamorphic/hydrothermal fluids and preexisting calcic skarns. The deposit provides excellent examples of mechanical control on ore localisation and of the complexity of ores in rocks with protracted thermal histories. Host skarns were produced by contact metasomatism around the 1740 Ma Burstall Granite, whereas the allanite–uraninite ore formed under amphibolite-facies conditions, late during the D2 phase of the ca 1550–1500 Ma Isan orogeny. Observations of ore geometry are consistent with previous geochronologic data demonstrating a large time gap between skarn formation and ore genesis. Numerical modelling of coupled deformation and fluid flow suggests that veins at the core of ore shoots may have formed as tensile or shear fractures during coupling of the competent skarn host with the late-D2 Mary Kathleen Shear Zone, allowing a change of orientation of ore shoots with distance from the shear zone. Mineral chemistry and petrographic observations suggest the possible role of a redox control on chemical localisation of ore by conversion of Fe2+-rich clinopyroxene-rich skarn host to Fe3+-rich secondary garnet ‘skarn’ and uraninite–allanite ore. Alternately, fluid pressure drops as a consequence of fracturing of the host skarn may have triggered fluid unmixing, or fluid mixing, leading to ore precipitation. Available data do not allow clear definition of the ultimate source of the U and REE, nor of the specific chemical ore-forming mechanism. However, regional constraints, previous Sm–Nd modelling, and our numerical models suggest a combination from proximal skarn hosts and from distal sources accessed by flow of metamorphic and/or late tectonic igneous-derived fluids. The deposit has some similarities with ironstone-hosted Cu–Au ± U deposits found in the nearby Cloncurry Belt.
Q-Index Code C1

Document type: Journal Article
Sub-type: Article (original research)
Collection: School of Physical Sciences Publications
 
Versions
Version Filter Type
Citation counts: TR Web of Science Citation Count  Cited 44 times in Thomson Reuters Web of Science Article | Citations
Scopus Citation Count Cited 43 times in Scopus Article | Citations
Google Scholar Search Google Scholar
Created: Tue, 10 Jun 2008, 13:47:14 EST