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Reactive transport model of silicification at the Mount Isa Copper deposit, Australia

pmd CRC. ENGINE, Potsdam, 12.01.2007. Reactive transport model of silicification at the Mount Isa Copper deposit, Australia. Michael Kühn 1,3 and Klaus Gessner 2,3 1 Applied Geophysics, RWTH Aachen University 2 School of Earth and Geographical Sciences, University of Western Australia

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Reactive transport model of silicification at the Mount Isa Copper deposit, Australia

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  1. pmdCRC ENGINE, Potsdam, 12.01.2007 Reactive transport model of silicification at the Mount Isa Copper deposit, Australia Michael Kühn1,3 and Klaus Gessner2,3 1Applied Geophysics, RWTH Aachen University 2School of Earth and Geographical Sciences,University of Western Australia 3Exploration and Mining, CSIRO

  2. Parallels between Soultz-sous-Forêts and Mount Isa • Fluid flow in fractured systems • Mineralization in crystalline rocks • Precipitation / dissolution pattern • Permeability evolution over time • Hypotheses testing applying reactive transport

  3. Outline • Mount Isa Copper – location, deposit, model • SHEMAT / Processing SHEMAT • Fluid flow driver? • Free thermal convection • Hydraulic head driven flow • Silicification pattern (quartz body development) due to the fluid flow driving process • Conclusion – What have we learned?

  4. Mount Isa location

  5. Mount Isa Copper deposit goCAD to SHEMAT 6 km x 5 km x 3 km Mount Isa fault Urquhart shaleenvelope Paroo fault

  6. Field observations – quartz body Urquhart shaleenvelope Mount Isa fault Paroo fault

  7. SHEMAT / Processing SHEMAT (Clauser 2003) • Coupled flow, heat, transport, and chemical processes • Geochemical reactions between solids and fluids • Reactive Transport • PHRQPITZ (Pitzer’s approach) for low to high salinities but seawater system only • PHREEQC (Debye-Hückel) for low salinities but increased chemical system

  8. Urquhart shaleenvelope Mount Isa fault Paroo fault Free thermal convection (high permeability Urquhart)

  9. Mount Isa fault Paroo fault Free thermal convection (low permeability Urquhart)

  10. Quartz body: observation vs. simulation high permeability Urquhart shale envelope Permeability controlling convection direction and in turn mineral alteration pattern. low permeability Mount Isa fault Paroo fault

  11. Urquhart shaleenvelope Mount Isa fault Darcy flux 1E-08 m/s free convection flux Paroo fault Forced flux / hydraulic head driven flow into faults

  12. Forced flux / no convection Forced flux / no convection 50 % impermeable Quartz body: observation vs. simulation One specific convection mode capable of producing quartz body but any forced flux mode.

  13. Conclusions • Process driving fluid flow? • free thermal convection • hydraulic head driven flow • Considering conditions required to form the observed quartz body suggests: rather hydraulic head driven flow than free convection

  14. Acknowledgements • Thanks to: • Florian Dobert who contributed to the presented work, • the pmd*CRC for financial support in previous years during my work with CSIRO, • Xstrata Copper for financial support and the contribution of valuable field data

  15. Thank you

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