A catchment analysis approach to the interpretation of regional stream sediment data: examples from the Canadian Cordillera

摘要

The geochemistry of a stream sediment sample reflects the integrated effects of eroding lithological units within the catchment basin from which it has been derived, their relative contributions to the stream sediment load, the de-coupling of elements during weathering and hydrodynamic sorting, and deposition/precipitation of secondary minerals. These processes all have the potential to mask subtle responses from commodity and pathfinder elements derived from mineral occurrences within a catchment. In addition, the catchment area relative to the area of exposed mineralisation within the catchment determines the degree to which a geochemical response related to that mineralisation is diluted. Several approaches have been developed to filter the masking effects of various processes affecting stream sediment geochemistry. These include the calculation of weighted average geochemical background for individual elements based on the relative proportions of each lithological unit exposed within the catchment, multiple regression analysis of stream sediment data given the areal extent of each lithological unit, levelling of geochemical data using the dominant lithological unit, and regression analysis of commodity or pathfinder elements against principal components that can be attributed to specific geochemical processes. Alternative approaches to the interpretation of regional stream sediment data include fractal analysis and the use of machine learning algorithms.