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Abstract

Although understanding the development of anomalous dispersion trains of gold in stream sediment is important to design and interpretation of exploration geochemical surveys, it has not been studied systematically with respect to variations in supply and transport of sediment. The problem is addressed by applying the sediment budget approach, with the following functional form: I(nput) - S(torage) = O(utput) Harris Creek, a gold-rich stream in south-central British Columbia was chosen as the study area. Primary sources of sediment are landslides in glacial deposits; secondary sources include bank erosion, erosion of sediment accumulated behind log jams, and sediment from tributary streams. Transport of bedload sediments within the Harris Creek drainage basin is strongly seasonal and dependent on the magnitude of the annual snowmelt flood. Field methods included collection of representative geochemical samples; direct field measurement of erosion; and collection of bedload samples using Helley-Smith samplers. Samples were analyzed in the laboratory to determine gold and magnetite. The data show that the supply of gold is discontinuous both spatially and temporally, with little or no gold being delivered to or transported out of Harris Creek during years with low or normal flood discharges (