The osmium isotopic composition of the continental crust

Osmium isotopic compositions and concentrations have been determined for deltaic and continental shelf sediments from three major rivers (the Amazon, Changjiang, and Mississippi) and for two loesses from the upper Mississippi River Valley. The loesses have heavy mineral and clay compositions characteristic of Mississippi river and delta sediment. Concentrations range from 15 to 120 pg Os/g, and 187Os/186Os ratios range from 8.2 to 10.9....