As we have seen.docx - As we have seen samples of...

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As we have seen, samples of particulate material in rivers can be used to obtain estimates of upper crustal composition. However, because the Sm/Nd ratio changes little during production of sediment, these sediment samples also contain information on the age of the rocks they are derived from through Nd model ages (or crustal residence time). Sm/Nd and 143 Nd/ 144 Nd ratios in major rivers draining about 25% of the exposed continental crust (excluding Antarctica and Australia) as well as samples of loess and aeolian dusts were analyzed by Goldstein and O’Nions (a different Steve Goldstein than the Steve Goldstein of the Goldstein and Jacobsen papers) are shown in Figure 16.11. The Nd isotope ratios are fairly homogeneous. Sm/Nd ratios are quite uniform, illustrating a point that was already well

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