Transport of magnetite and gold in Harris Creek, British Columbia, and implications for exploration

Abstract

Earlier studies have suggested that difficulties sometimes encountered in following up anomalies can result partly from large seasonal variations in gold content of stream sediments. This possibility has been investigated using pit traps installed in a bar on Harris Creek, British Columbia. Sediments caught in the traps in 1988 and 1989 provide data on variations in concentrations of gold and magnetite in bedload as stream discharge changes. These show that anomalous concentrations of gold are only transported for brief periods when increased discharge, caused by snowmelt floods, disrupts the cobble-gravel pavement. For the purposes of exploration geochemistry, these flood sediments, trapped in the voids of the newly formed pavement as the flood peak passes, provide the best chance of recognizing the presence of anomalous concentrations of gold in a catchment. However, their subsequent burial by post-flood gold-poor sediments may cause seasonal variations in gold content of near-surface sediments.