From source to sink: evolution of fluid systems in the Eastern Succession

Transcription

1 pmd CRC From source to sink: evolution of fluid systems in the Eastern Succession Nick Oliver, Kris Butera, James Cleverley, Lucas Marshall, Mike Rubenach, Bill Collins & Bin Fu Presented as part of the Mount Isa PDT meeting, March 2005

2 1 B.C.

3 (a) (b) E Little Beauty Syncline B E L T Mt Godkin Granite S - Cameron Fault N MARY KATHLEEN 5 km MOUNT ISA CLONCURRY S - Stop 1 Blockade WESTERN MKFB SUCCESSION BASEMENT DUCHESS EASTERN FOLD BELT 100 km Stop 3 Gilded Rose Wonga Fault Stop 2 Mary Kathleen U-REE Mine U Burstall Granite Mary Kathleen Syncline Corella Fm and equivalents Other metasediments, metavolcanics Pre-Corella basement Proterozoic metagranitoids Rosebud Syncline Fountain Range Fault Corella Fm Thermally metamorphosed Corella Fm Argylla Fm Mafic meta-intrusive rocks Burstall Suite Granitoids Wonga Granite

4 Marshall (2003): Carbonate veins, all ages, converging upon magmatic/mantle values Retrograde/ meteoric 1 limestone Magmatic/ mantle BIF Black shale

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7 Physical and isotopic evidence of old ore easy to find at Osborne, Starra, Eloise

8 But only isotopic evidence at Ernest Henry (old sulphur but new copper?): breccia attributes similar to Williams-related breccias (Oliver et al. ARC work)

9 Regional carbonate (pyrrhotite) vein systems: red herrings or John Walshe s mantle juice?

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11 py Au: 1000, 100, 1 ppb ht Dissolution of orebodies and disseminated sulphides by acid, oxidized saline fluids during Williams emplacement f O ppm Cu po 1 ppm Cu mt ph Pre- to syn-1600 Ma ore deposition by interaction of reduced fluids with rocks

12 Au: 1000, 100, 1 ppb ht Oxidised fluids get reduced by wallrock reaction (albitization) -25 f O py 100 ppm Cu po 1 ppm Cu mt ph Reduced fluids: HCOS from mantle or leaching of mafic rocks: 1686 sulphur source at EH?

13 1600 Ma and Williams-age fluids: impact on earlier sulphides

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15 Fluid mixing remains the most likely process to make Ernest Henry Fluctuating Ba and sulphur (barian( feldspar and barite) very low barite solubility requires separate Ba and S sources Fluctuating As (zoned arsenical pyrite) Brecciation as the mixing chamber If sulphur derived locally from c or 1650 Ma sources, it was carried in fluid to ore deposition site over distances at least as large as the orebody system

16 Annoying pollutant: surface fluid Br/Cl, or is this scapolite precipitation (or biotite?) during ore formation? Carbonic mantle fluid drives sulphur dissolution and transport Williams Batholith fluid drives energy and copper Ernest Henry

17 Mafics, ironstones & early sulphides recycled by oxidised fluids Explosive overpressure drives fluidised breccias, oxidised, S-poor fluid Mafic/felsic mingling: Cu & CO2 transferred into late stage magmatichydrothermal fluid: big volume release upon exsolution High % crystallisation in granite, Evolves saline brine Granite source region Moho Underplated mafic melts

18 Carbonatitic HCOS fluids Granite source region Moho Underplated mafic melts

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20 OBSERVING REAL WORLD ARCHITECTURE SURFACES Faults Contacts eg unconformities + ROCK TYPES and PROPERTIES FLUIDS ALTERATION - Footprints -3D Distribution + GREATEST WEAKNESS IS LACK OF KNOWLEDGE MAPS!!! MINERAL SYSTEMS PROCESS THINKING CONCEPTUALISING AND SIMULATING CREATE 3-D MAP Create Holistic 3D-Map from observations and other data/ knowledge DETERMINE HISTORY RESTORE RESTORE 3D Maps to time of Mineral deposition SIMULATE NUMERICAL AND MATHEMATICAL MODELLING TRANSLATE RESULTS TO EXPRESSIONS IN REAL WORLD TRANSLATE RESULTS AND PROCESSES INTO OBSERVABLE CRITERIA: FOR TARGETTING DEPOSIT MINERALOGY REDUCING RISK FOR EXPLORATION AND INCREASING CONFIDENCE IN TARGETING

21 QDSDI initiative QDNRME Industry CSIRO JCU?pmdCRC QPSF All minerals/energy databases to digital Access, data storage and recovery Information, visualisation Geometry/structure/ thermal Minerals prospectivity 3DGIS 3D models Q3D Knowledge layers to GIS Process modelling Targeting Define vectors to discovery Geometry/structure/strat Oil & gas prospectivity 3DGIS 3D models Data transfer Interoperability Remote access supply and technologies Web services