ASSESSING MULTI-STAGE ORE FORMING PROCESSES USING LA ICP-MS SULPHIDE ANALYSIS IN OROGENIC GOLD DEPOSITS AND APPLICATIONS TO EXPLORATION
Résumé
Quantitative laser ablation inductively coupled plasma-mass spectrometry (LA ICP-MS) element distribution analyses performed as map and/or traverse mode provide only visual insight into both distribution and relative timing of trace element inputs during sulphide formation (growth zoning, core, fractures etc.). An innovative technique based on compilation and treatment of the individual time-slice data (TSD) extracted from these elemental analyses have been recently developed to better identify elemental paragenesis and assess multi-dimensional element coupling/decoupling processes and corresponding mineralizing events. To further understand complexities of mineralization, application of geostatistical tools (e.g., multidimensional scaling, principal component analysis, linear discriminant analysis) and various innovative multi-element binary plots have been also produced.
As major results, such analyses applied to various gold-bearing sulfides from a variety of orogenic gold settings (BIF- and slate-hosted gold deposits) demonstrate that: 1) gold mineralization reflects multi-stage processes; 2) elemental associations vary as mineralization progresses, such as the early growth history of sulphides versus later coupled dissolution-precipitation reactions; and 3) different metal-source reservoirs and stratigraphy influence the fluid signature. These results contribute to better decipher the complex processes involved in the protracted evolution of orogenic-type gold systems.