Abstract

The concentration of heavy minerals in a sedimentary deposit depends, inter alia, on the composition of the source material, local hydraulic conditions during deposition, sizes and densities of the sediment grains, and sizes of the grains relative to the bed roughness. Effects of these factors have been investigated in a laboratory flume by depositing pure heavy mineral and mixed heavy and light mineral sediments on a stationary granular bed. Experiments with pure heavy minerals indicate that once a minimum mobility condition is exceeded, deposits will be fairly extensive and uniform, and only slightly affected by the flow condition. In all experiments, deposits were generally finer grained than the supply sediments and, in some cases, were bimodal. The concentrations and total amounts of heavy mineral in the deposits were influenced by the concentrations in the supply mixtures and were strongly dependent on the sizes of the light mineral grains. The results show that settling velocity is a poor indicator of hydraulic equivalence, while critical shear velocity appears to be a good indicator.

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