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 Microanalysis can provide rapid, quantitative characterization of mineral systems that complements the field- and core-scale observations traditionally made in ore deposits. We review recent innovations in microanalytical procedures and their application to studies of ore deposits. Case studies are presented examining how microanalysis can provide constraints on macroscopic processes within mineral systems. Synchrotron X-ray fluorescence shows centimetre-scale chemical variations associated with proximity to mineralization in samples from Sunrise Dam Gold Mine, Western Australia. Pseudomorphs of igneous plagioclase and chemically driven recrystallization interpreted from electron backscatter diffraction suggest that the system was dominated by fluid-driven brecciation with very little shearing. Both the fluid chemistry and fluid pressure evolved during a protracted sequence of vein formation and alteration accompanying gold mineralization. A second case study of sulphide mineralogy at the Mt Keith nickel sulphide deposit, Western Australia demonstrates how X-ray computed tomography combined with trace element mapping can constrain the chemistry and dynamics of magmatic systems. Large-scale interaction between silicate and sulphide melts, shown by homogenous palladium enrichment in pentlandite, leads to a large proportion of globular ores with a high nickel content. Increasing use of microanalysis in ore deposit geology is resulting in the constant reassessment of established models for ore genesis though a combination of micro- and macroscale datasets.