Characterization of the MAX porphyry Mo deposit using trace element geochemistry in hydrothermal alteration minerals, Trout Lake, B.C.

Abstract

Over the last few decades it has become increasingly difficult to discover new ore deposits and as existing deposits are exhausted, techniques for improving exploration success are becoming vital. In this study I investigated the application of trace element mineral geochemistry, in the context of well-defined petrology and field mapping, to the identification and characterization of hydrothermal alteration of a small porphyry Mo deposit located in southeastern B.C., Canada. Detailed geochemical analysis of the MAX Mo-porphyry deposit was undertaken and the use of trace element geochemistry signatures of hydrothermal alteration minerals were established. Ninety-six samples were collected from surface, underground and drill core and graphic core logging was carried out on five holes. Whole rock geochemistry was obtained for all samples in order to observe any general alteration trends. The trace element concentrations of quartz, chlorite and epidote were analysed using laser ablation inductivelycoupled plasma mass spectrometry. Cathodoluminescence was used to show textural differences and growth zoning in quartz and to observe different generations of quartz. The results indicated that in hydrothermal quartz Ti, Al and Li showed systematic increases in concentration towards the porphyry center and could be used to infer the temperature of formation. The concentrations of Ti, Al, Li, Ge, Mg and Fe could be used to distinguish between different types of quartz. Hydrothermal quartz showed the most variance when it came to concentrations of individual trace elements, whereas regional metamorphic quartz that was unaffected by hydrothermal alteration had the lowest concentration of trace elements and a uniform trace element chemistry regardless of proximity to the deposit center. Igneous quartz was depleted in Ge relative to hydrothermal and metamorphic quartz. For chlorite it was found that Ti, V and Sr concentrations varied depending on distance from the porphyry center. Both Ti and V decreased in concentration away from the deposit center, whereas Sr peaked around 350 - 400 meters and then decreased away from the deposit center. The trace element alteration vectors identified in this study combined with subtle, but identifiable, field criteria may assist exploration companies in the search for hidden deposits.