Abstract

Unlike drainage basin area, stream order has not been quantitatively integrated in analysis of stream sediment geochemical data. It is hypothesized here that stream order is a useful surrogate for drainage basin area in ‘correcting’ for sediment dilution in order to detect stream sediment geochemical anomalies. Geochemical residuals, derived from catchment-based background corrections, are multiplied with respective sample site stream order to obtain stream-order-‘corrected’ residuals, which are compared and contrasted with corresponding values of productivity of a drainage basin. The validity of the hypothesis is tested and demonstrated in a drainage basin in the Aroroy gold district in the Philippines. There are strong and statistically significant correlations between stream-order-‘corrected’ residuals and values of productivity. Anomalous areas based on uni-element stream-order-‘corrected’ residuals are spatially identical or strongly spatially similar to anomalous areas based on uni-element values of productivity. Multi-element associations extracted from stream-order-‘corrected’ residuals are identical or highly similar to multi-element geochemical associations that can be extracted from values of productivity. The results of the study demonstrate that routine calculations of stream-order-‘corrected’ residuals would be particularly useful for interpretation of reconnaissance stream sediment geochemical data derived by sampling low-order streams.

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