Abstract

The elemental composition (Ti, Fe, Mn, Mg, V, Zn, Cr, Ni, and Cu) of detrital ilmenite grains from three large drainage basins in Virginia was found to be relatively unchanged over hundreds of kilometers distance downstream from the Blue Ridge Mountains to the Coastal Plain. The igneous Blue Ridge Complex apparently contributes a sufficient quantity of ilmenite in each river system such that the input of distinctly different ilmenite compositions from tributaries does not change the overall ilmenite composition in the main river. This is not the case for nonopaque heavy minerals, which change in abundance and type downstream due to tributary input. Despite a similar primary source, each major river has a distinctly different ilmenite composition which can be discriminated at better than a 0.95 confidence level. This enhances the ability to determine the source river for sands in the depocenter. Initial results on ilmenite from small-drainage-basin tributaries dominated by one or two source-rock types known to contain ilmenite show that compositional differences exist for granitic, mafic igneous, metamorphic, and sedimentary sources.

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