Abstract The spatial distributions of mineralization and alteration in hydrothermal systems are complex and are often considered to be cryptic and problematic to quantify. We used wavelet analysis of conventional hyperspectral drillcore logs to demonstrate quantitatively that primary Au mineralization, common vein-hosted mineralogy (calcite and ankerite), host rock alteration mineralogy (sericite and chlorite) and regional-scale metamorphic assemblages (amphibole) organize spatially as multifractals. This documentation of multifractal spatial organization in Au and alteration mineralogy is sufficient to show that they are the result of underlying deterministic dynamic processes as opposed to random stochastic processes. The application of wavelets to three ore bodies (GQ, Vogue and Cosmo East) from the highly endowed Archaean Sunrise Dam hydrothermal Au system of Western Australia shows that the spatial organizations of Au and ankerite are more closely associated in GQ than in Vogue. The spatial organization of Au in Vogue is more strongly associated with calcite. Primary Au mineralization and infill carbonate mineralogy are more complexly organized than sericitic and chloritic host rock alteration. Although demonstrated here for a hydrothermal system, wavelet analysis is readily applicable to downhole or outcrop data from any deposit type.

Abstract The Cadillac mining camp is known for its numerous, but relatively small, orogenic gold deposits, which are spatially associated with the Larder Lake-Cadillac fault zone. The Lapa deposit, with a total endowment of 36 t Au (1.15 Moz), represents the largest gold deposit of the Cadillac mining camp. The Lapa deposit main ore zones are mostly hosted in the Piché Group ultramafic to intermediate volcanic units that are strongly transposed and separated by subvertical, anastomosed high-strain corridors that are part of the Larder Lake-Cadillac fault zone. There are 12 ore zones that are stacked from north to south, forming a series of subparallel, E-striking (main foliation-parallel), steeply dipping south to subvertical “lenses.” The ore consists mainly of very fine-grained (≤1 mm), disseminated sulfides (arsenopyrite and pyrrhotite with traces of chalcopyrite, pyrite, and sphalerite), sulfosalts, native Au, and native Sb. Three amphibolite-grade metamorphosed proximal alteration assemblages are present at Lapa, namely bio-tite-bearing, sericite-bearing, and actinolite-bearing assemblages. The distribution of the three assemblages, defined by the most abundant mineral, is at least in part controlled by the primary host-rock composition. The proximal alteration facies give way to chlorite- (upper half of the deposit at <1,000 m) and hornblende-bearing (lower half of the deposit at >1,000 m) assemblages a few meters to a few decimeters away from the ore zones. The isograd defined by the presence of actinolite in the proximal alteration assemblage and hornblende in the distal assemblage below 1,000 m correlates with a shift from an Au-As association in the lowermost levels of the mine to an Au-Sb association at depth. This variation is thought to be due to varying heat and fluid flow regimes at different times and crustal levels in the fault, with the upgrading of early, “low-grade” Au during prograde and retrograde metamorphism. The Cadillac camp, including the Lapa deposit, is an excellent example of the camp to deposit to stope controls exerted by the structural and lithologic setting on the nature, style, and geometry of greenstone-hosted orogenic gold deposits.