The Things that Matter Architecture and Chemistry Peter Neumayr, John Walshe, Steffen Hagemann
Glen Masterman Kanowna Belle Masterman, Embedded Researcher Louis Gauthier, PhD Golden Mile Sian Nichols*, Honours New Celebration Mehrdad Heydari, PhD Ultramafic Rocks Joanna Hodge, PhD Alteration-Fluid Framework Kate Moran, Honours St Ives Fire Brigade Peter Neumayr John Walshe Steffen Hagemann Leo Horn, Embedded Researcher St Ives 2004 Susan Drieberg Wallaby Drieberg, Embedded Res.
predictive redictive ineral iscovery Goal: Goal More Cost effective Method: Method exploration Answer 5 Questions Kalgoorlie-Kambalda Key Themes: Laverton Scale integrated structural-hydrothermal Scale Integrate alteration models Quantitative Chemical gradients Contrasting fluid systems Understanding Empowered by embedded researchers on site and University-based research and training Eastern Goldfields
Aim: Develop Ore Systems View of Goldfields 5 QUESTIONS: AGCRC heritage Architecture Geodynamic Reservoirs Fluids drivers Transport /deposition
predictive Architecture of depositional site & intrusive complexes Seal Mixing Box Au?? Au?? Integrate upper crustal architecture with deep-crustal architecture
predictive Blewett, pmd2003 CRC
3D Architectural controls on reservoirs fluid pathways, chemical gradients Challenge: District - Terrane Scale Models
KB: Felsic Hosts; SIG: Mafic Hosts predictive Redox Range of Alteration Redox(log fo2) -22-24 -26 SO2g - H2Sg HSO4 -H2S Hematite Magnetite CO2g-CH4g Oxidized Fluids Volatiles Oxidized Magmatic Volatiles SIG: Fsp-Au High V/Al in magnetite Low V/Al in magnetite SIG: Wallrock approx. SIG: Ep Magnetite Po KB: V-rich Phengite+/- Fsp Reduced Fluids -28-3 -2.6-2.2-1.8-1.4-1 -0.6-0.2 Sum S { log(h2s+sulfate) } Pyrrhotite Hematite Pyrite KB: Fsp +/-V-poor Phengite Pyrite 400ºC, 500 bars
predictive Early Epidote-Carbonate Carbonate- Magnetite Alteration WR GC 30000 25000 20000 1 0 carb ep fsp un 800 600 Ep-carb-mag 0 carb ep fsp un Te 15000 10000 2 Sr 400 Fsp-carb-py-Au 5000 3 200 0 0 1000 2000 3000 Au 0 0.00 0.05 0.10 0.15 0.20 0.25 Na Te 30000 25000 20000 15000 10000 5000 0 0 10 20 30 40 50 Bi 0 carb ep fsp un associated with porphyries pre-dates gold Bi-tellurides Sr-rich, Na-poor St. Ives
predictive Exploration: Te-Au Most Te separate event to Au But spatially similar Te still good proxy for Au St. Ives Au Te Down Hole Depth (m). 100 150 200 250 300 350 1000 12000 LD7114 23000 0 50 100 150 200 250 300 6000 2000 LD7113A 10000 280 300 320 340 360 1600 1000 400 LD70026A
predictive Early Epidote-Carbonate Carbonate-Magnetite Alteration FC (PIXE) 150 100 Zn 50 Ca K 0 Ep-Mag Syn-Au 0 50 100 150 Cu 6000 Ep-Mag Syn-Au 5000 4000 Sr 3000 Fe Sr 2000 1000 0 St. Ives 10000 30000 50000 70000 Ca
predictive Fsp-Carb Carb-Py-Au alteration WR GC Albite 1.0 0.8 bio chl chl_bio no 25 Size of symbol indicates Au grade bio chl chl_bio no 20 Na.Al 0.6 0.4 Cs 15 10 0.2 5 0.0 0.0 0.2 0.4 0.6 0.8 1.0 K.Al St. Ives Muscovite 0 K feldspar 0.2 0.4 0.6 0.8 1.0 Fe/(Fe+Mg) Na/Al vs K/Al plots map out biotite/chlorite alteration zones Fe/(Fe+Mg) ratios map out Au-related biotite/chlorite: Au occurs with intermediate compositions Cs does not correlate with Au-related biotite
Au 10 ppm Probed Chlorite Compositions 200 Fe/Fe+Mg 0.25 0.3 0.35 0.4 0.45 0.5 250 Depth(m) 300 350 400 CD10095W2 (Conqueror) Au Grades correlate with zoning in chlorite compositions picked up by PIMA PIMA
KB: Felsic Hosts; SIG: Mafic Hosts predictive Redox Range of Alteration Redox(log fo2) -22-24 -26 SO2g - H2Sg HSO4 -H2S Hematite Magnetite CO2g-CH4g Oxidized Fluids Volatiles Oxidized Magmatic Volatiles SIG: Fsp-Au High V/Al in magnetite Low V/Al in magnetite SIG: Wallrock approx. SIG: Ep Magnetite Po KB: V-rich Phengite+/- Fsp Reduced Fluids -28-3 -2.6-2.2-1.8-1.4-1 -0.6-0.2 Sum S { log(h2s+sulfate) } Pyrrhotite Hematite Pyrite KB: Fsp +/-V-poor Phengite Pyrite 400ºC, 500 bars
predictive redictive ineral iscovery Porphyries and magnetite
predictive redictive ineral iscovery Redox-mapping DFD KSL Magnetite (no seds) Magnetite? Porph. Extremely reduced? DCB KAM PBS * Pyrrhotite Pyrrhotite (no seds) BFS LUN 2km. Porph.? Reduced Exploration near mine
predictive Exploration district scale KB_Reg_PIMA_modified by Chlorite_yFeOH 2,255 to 2,261.3 Fe-chlorite (170) 2,250 to 2,255 Int-chlorite (615) 2,245 to 2,250 Mg-chlorite (399) 2,238.7 to 2,245 (97) Mapping with PIMA, bottom of hole geochemistry 2 km Kanowna Belle
predictive Whole-rock and Fluid Chemistry - Concept Whole-rock geochemical analysis Fluid analysis KB_Reg_PIMA_modify by mica_xt 5 to 14.2 (157) 2 to 5 (554) 1 to 2 (550) 0 to 1 (488) 1km INPUT Geochemical Modelling Genetic Model Exploration Model
predictive Conclusions Spatial and temporal variations in fluid chemistry Gradients win!!! Map flow paths & reservoirs Build Scale Integrated Models!!! Tools: Alteration mapping (PIMA, Core Logger) Whole-rock geochemistry Isotopes S,C & O