By their very nature, hydrothermal ore deposits are located in environments characterized by at least transiently enhanced permeability and focused fluid flow. As a consequence, it is the norm for deposits to have experienced multiple flow events making the interpretation of fluid inclusion data and hydrothermal evolution difficult. Cathodoluminescence of quartz using an SEM-mounted CL detector can be used as a powerful tool to help resolve complex fluid histories. The application of SEM-CL can be done over a range of scales, from the growth stage (mm-scale) to the growth zone (100’s of microns) and even down to individual microfractures (a few microns). The establishment of petrographic relationships between precipitation events differentiated by their CL signatures allows temporally-constrained fluid inclusion data to be collected. In the ideal case, all fluid inclusions become “primary” with respect to their host, be it quartz within a growth zone or quartz healing a secondary microfracture. This methodology has been used to resolve a number of processes in vein gold deposits: the transition from homogeneous H₂O-CO₂ fluid to fluid unmixing, the progressive mixing and dilution of H₂O-CO₂ fluids, and low temperature brine overprinting and gold remobilization. The future application of the methodology will provide a powerful way of unravelling the complex chemical evolution of ore-forming solutions that laser ablation microanalysis has the potential to reveal.