Trace element variation in ore minerals from the Iron Cap deposit (KSM), British Columbia, Canada: Implications for fluid evolution in porphyry-epithermal gold systems

Trace amounts of elements such as As, Sb,Se, Te, Pd, Hg and Au are commonly identified in porphyry and epithermal mineral deposits. Investigating variations in the concentration, distribution and hosting of these elements in an ore mineral suite has the potential to enable elucidation of the specific characteristics of discrete fluids throughout the evolution of a mineralizing magmatic-hydrothermal system. The Iron Cap deposit in the Kerr-Sulphurets-Mitchell (KSM) district, British Columbia, Canada, provides an opportunity to interpret the characteristics of hydrothermal fluids from an early porphyry stage, through transition, to a late epithermal stage. A suite of 60 core samples are characterized by petrographic methods to constrain the sequence of vein formation at Iron Cap, and identify deposit mineralogy. The results of initial trace element analysis of ore minerals by SEM-EDX analysis has shown that pyrite growth zones are Cu-or As-bearing, and arsenopyrite growth zones have a variable Fe:As:S ratio. Galena commonly contains Se, ranging in concentration from ~2wt. % to clausthalite (PbSe). Additionally, gold in the deposit contains between 2-42 wt. % Ag. These initial discoveries will allow a methodology to be developed to interpret fluid conditions with trace element variations.