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Liam Courtney-Davies (Curtin University) on: Micro- to nanoscale geochronology in and around the Olympic Dam Cu-U-Au-Ag deposit, South Australia

By Hugo Olierook 10 March 2021 Applied Geology Comments Off on Liam Courtney-Davies (Curtin University) on: Micro- to nanoscale geochronology in and around the Olympic Dam Cu-U-Au-Ag deposit, South Australia

Wed 17th March 2021 @ 12:00 nn in 312.222 and online via Webex (meeting #: 184 504 2665 and password: NZtPPEpY842)

Abstract:

The diverse clan of ore deposits classed iron oxide copper-gold (IOCG) systems are among the most heavily studied type of deposit, yet, there is little consensus on the fluid sources, mechanisms and timescales by which they form. This is due to their geology; intense metasomatic alteration and auto brecciation of ostensibly any host rock type, whereby, conventionally dateable phases that precipitate at the prevailing conditions during ore formation do not survive or simply do not form. The archetypal example of an IOCG system sensu stricto is the 1.59 Ga Olympic Dam deposit, the world’s largest published U, 3rd largest Au and 5th largest Cu resource.

We show that IOCG formation, using Olympic Dam and related deposits as case studies, can be dated at high-precision repeatably via application of the hematite-zircon U-Pb geochronometers with (CA)-ID-TIMS. Hematite U-Pb systematics are investigated down to the nanoscale to confirm U and radiogenic Pb is lattice bound and unaffected by post crystallization processes. Constraints highlight the timescales of magmatic to hydrothermal transition and possible mineralization lifespans in IOCG systems. This transition is also recorded at the nanoscale in magmatic zircon, often manifest as pervasive Fe-Cl alteration products, which can coexist with metallic-Pb nanospheres produced via high-T metamorphism. New findings on the nature of metallic-Pb nanospheres within and around ore systems applying FIB-HAADF S/TEM techniques will be discussed.

Short bio:

Liam received a M.Sci. in Geoscience from Royal Holloway, University of London (2015), and a Ph.D. from the University of Adelaide (School of Chemical Engineering and Advanced Materials; 2019). His doctoral research centred upon development and application of iron-oxide U-Pb geochronology and synthesis/characterization of U-Pb reference materials. He began a postdoc at the JdLC in November 2019 addressing the geochemistry and chronology of iron ores in the Hamersley Province, WA.

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