4/16/2023 0 Comments Breaktime miner moThe main quartz-plagioclase porphyry dyke in the open pit, mineralized over a strike-length of more than 1 km, was boudinaged after emplacement at 2676 ± 7 Ma. The correlation of meta-gabbro sills in the isoclinal D1 Celebration Anticline indicates 12 km of left-lateral offset ( Figure 1). District-scale mapping established that the deposit is located in the main branch of the Boulder Lefroy Fault. Underground production from the northern lease amounts to 0.893 million metric tons (Mt) at 7.83 g/t gold (1897–1996), and the combined open pit production to 20.3 Mt at 2.17 g/t (1986–2009). Gold-related albite-altered porphyry dykes (albitites) also occur in the world-class Hollinger-McIntyre (986 t Au) and Kerr Addison-Chesterville deposits (336 t Au), Abitibi greenstone belt, Canada. These relationships are interpreted to indicate syn-mineralization emplacement. Temperature estimates based on actinolite-albite pairs (300–350 ☌) agree with the fluid inclusion trapping temperature of main-stage auriferous veins (330 ± 20 ☌). Above the sample site, the dyke was mined as gold ore (1–6 g/t Au) at +300–350 m. It contains auriferous pyrite (70 ppb Au 610 ppb Ag) where sampled for zircon U-Pb chronology at +224 m elevation. The younger porphyry locally crosscuts foliation and is bordered by post-kinematic actinolite-pyrite selvages overprinting talc-chlorite-phlogopite-dolomite schist. The sodic-potassic alteration of the felsic boudinaged dyke contrasts with the albite-actinolite alteration in the adjacent mafic (high Cr, Ni, V) plagioclase porphyry dated at 2662 ± 4 Ma, although both share the same sulfide-oxide assemblage: pyrite ± chalcopyrite, magnetite ± hematite. Ore-grade biotite-carbonate and late sericite-carbonate-alkali feldspar replacement is bound to the contacts of a felsic (low Cr, Ni, V) quartz-plagioclase porphyry dyke dated at 2676 ± 7 Ma. The New Celebration deposit (51 t Au) is part of a group of hematite- and anhydrite-bearing mesothermal deposits and Fe-Cu-Au skarns associated with monzodiorite-tonalite intrusions in the strike-slip fault system. The Boulder Lefroy-Golden Mile fault system in the Archean Yigarn Craton is the most productive gold-mineralized structure in Australia (>2300 t Au).
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