Definition, geometry and parameterization of alteration envelopes around VMS deposits in the Matagami camp

Alteration halos are often much larger than the associated mineralization. This is particularly true for volcanogenic massive sulphide (VMS) deposits, where mineralized lenses (on the order of a hundred metres in diameter) are enclosed in halos, often kilometre-scale. However, it is important to differentiate proximal chloritization halos and distal sericitization halos. Numerous scientific studies and many CONSOREM projects, including this one, have focused on the characterization of the hydrothermal footprint. Thus, dozens of methods exist to qualify and quantify alteration (Mathieu, 2018). Most are based on mineralogical transformations of plagioclase to sericite and sericite to chlorite. However, few studies have focused on the geometry of the envelope, especially in 3D. This has major implications for exploration (mineral potential maps, potential to detect halos during regional exploration programs, etc.).