A Sm-Nd isotopic study of atmospheric dusts and particulates from major river systems

Nd-143/Nd-144 ratios, together with Sm and Nd abundances, are given for particulates from major and minor rivers as well as continental sediments and aeolian dusts collected over the Atlantic, Pacific, and Indian Oceans. In combination with data from the literature, the present results have implications for the age, history, and composition of the sedimentary mass and the continental crust. It is noted that the average ratio of Sm/Nd is about 0.19 in the upper continental crust, and has remained so since the early Archean, thereby precluding the likelihood of major mafic-to-felsic or felsic-to-mafic trends in the overall composition of the upper continental crust through earth history. The average 'crustal residence age' of the entire sedimentary mass is about 1.9 Ga.