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Predictive Mineral Discovery COOPERATIVE RESEARCH CENTRE Scale-Integrated Alteration Studies at Kanowna Belle Dr

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Predictive Mineral Discovery COOPERATIVE RESEARCH CENTRE Scale-Integrated Alteration Studies at Kanowna Belle Dr predictive mineral discovery COOPERATIVE RESEARCH CENTRE Scale-Integrated Alteration Studies at Kanowna Belle Dr. Glen Masterman and Scott Halley (Placer Dome Asia Pacific) John Walshe (CSIRO) KB Sulfide Evolution KB Sulfur Isotopes YilgarnSulphurIsotopes_AMG by d34s Kanowna Belle 4 to 20.5 (115) -1 to 4 (415) -4 to -1 (175) 1000 -41.6 to -4 (233) 100 dirty 10 zoned clean Au ppm 1 unclassified 0.1 0.01 -8 -4 0 4 8 δ34S N •Dirty pyrite cores with Au, Te, basemetal & Kanowna Belle; Sulfur Isotope values gangue inclusions 40 KB •As-rich and As-poor growth bands 35 •Clean inclusion-free euhedral pyrite 30 2 km 25 KB overgrowths 20 Regional •Late Au, Te & sulfosalt infill (remobilised or 15 •High Au grades correlate with -ve δ34S values in dirty pyrite cores. new addition??) No. of measurements 10 34 5 •δ S values in zoned pyrite are between -2.8 and 2.9 per mil. 0 •Clean pyrite rims are -2.5 to 0.3 per mil. 0 2 4 6 8 -8 -6 -4 -2 10 -12 -10 δ34S •KB pyrites record a history of oxidised fluids early in the evolution of the deposit gradually becoming swamped by reduced fluids. •Regional δ34S values are clustered around 2 per mil KB Alteration Geochemistry Lowes Shoot Alkali Signature (GDD438) Lowes Shoot Pathfinder Signature (GDD438) KB Regional Alkali Halo Muscovite V-rich + alkali feldspar altered samples Albite KB Muscovite-albite tie line 2 km A plot of K/Al vs. Na/Al molar ratios quantifies alteration Pathfinder elements typically associated with Au include W, Mo, mineralogy. Te, Bi, Sb and As. V-rich, alkali feldspar + high K/Al muscovite Regional multielement geochemistry highlights several areas around There is too much K in samples above the tie line for muscovite. alteration occurs proximal to gold mineralisation. The distal KB with similar alteration signatures. These samples must contain a component of K feldspar, i.e., the signature is characterised by low K/Al, Ba-rich sericite ± albite. feldspar = alkali (Na + K) feldspar. KB Short Wave Infrared (SWIR) Spectral Mapping KB_Reg_PIMA_modified by Sericite_YAlOH KB_Reg_PIMA_modified by Sericite_YAlOH Lowes Shoot SWIR AlOH Wavelengths 2,208 to 2,223 phengite (1013) 2,208 to 2,223 phengite (1013) 2,200 to 2,208 muscovite (795) 2,200 to 2,208 muscovite (795) 2,195 to 2,200 paragonite (233) 2,195 to 2,200 paragonite (233) 2,188.1 to 2,195 (88) 2,188.1 to 2,195 (88) Phengite 1-4 g/t Au >4 g/t Au Muscovite N N KB 250 m •White mica AlOH absorption wavelengths across Lowes Shoot are zoned from phengitic compositions (2212-2216 nm) to muscovitic compositions (2200-2204 nm). 2 km •Gold in Lowes Shoot occurs predominantly within phengititc white mica domains near the tranistion to muscovitic AlOH wavelengths. The correlation between gold and white mica gradients is evident at all The regional KB spectral map is dominated by a cell of phengitic white •Ore-related phengites have elevated V (650 ppm), Mg (2 wt. %) scales across KB. mica alteration surrounded by a muscovite envelope. The transition to and high K/Al ratios (0.38 - 0.40) relative to muscovite (V = 250 muscovite alteration occurs along the major D1/D2 structures. KB is ppm, Mg = 0.5 wt. %, K/Al = 0.33) in the distal envelope. situated on the edge of the phengite plume in a strong white mica •Barium contents (2800 ppm) are higher in distal muscovite than gradient in proximal phengite (1500 ppm). KB_Reg_PIMA_modified by mica_xt KB_Reg_PIMA_modified by Chlorite_yFeOH 5 to 14.2 (157) 2,255 to 2,261.3 Fe-chlorite (170) •A map of the mica crystallinty index shows that highly crystalline 2 to 5 (554) 2,250 to 2,255 Int-chlorite (615) 1 to 2 (550) 2,245 to 2,250 Mg-chlorite (399) 0.05 to 1 (488) 2,238.7 to 2,245 (97) micas occur in the core of the phengite cell. Low crystallinity white 0 to 0.05 (1798) micas occur around the edges. •We interpret variations in white mica crystallinity to reflect a temperature gradient from high in the core to low around the edges. Low temperatures on the margins possibly caused pH to decrease below phengite stability to muscovite. The transition from V-rich phengite (oxidised) associated with ore to Ba-rich (reduced) muscovite implies that a redox gradient controlled the composition of white micas. Overlapping redox, pH and temperature gradients at KB N N are inferred to have influenced gold deposition. KB KB •Chlorite FeOH absorption wavelengths indicate that Mg-chlorites are centred predominantly in the core of the hydrothermal cell. Fe- chlorites are zoned around the edges and along the D1 structures. 2 km 2 km •The distribution of Mg- and Fe- chlorites represents a temperature gradient consistent with that depicted by white mica crystallinity. predictive mineral discovery www.pmdcrc.com.au.
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