Depleted mantle lead isotopes

Radiogenic isotopes, on the other hand, show differences between crust and mantle reservoirs which are a function of long-lived differences in parent/daughter element ratios and indicate the isolation of the reservoirs from one another for long periods of Earth history. This gives rise to crustal reservoirs which generally are enriched in Sr/ Sr and in radiogenic lead isotopes but depleted in Nd/ Nd relative to the mantle. 

The HIMU component in the magma sources of the mantle has an elevated Pb/ Pb ratio presumably because it has a high W Pb ratio which isotope geochemists call mu (p), hence the name HIMU. The apparent emichment of the HIMU mantle component in uranium (or its depletion in lead) have been alternatively attributed to ... 

Figure 3 Crust-mantle differentiation patterns for the decay systems Rb-Sr, Sm-Nd, Lu-Hf, and Re-Os. The diagram illustrates the depletion-enrichment relationships of the parent-daughter pairs, which lead to the isotopic differences between continental crust and the residual mantle. For example, the Sm/Nd ratio is increased, whereas the Rb/Sr ratio is decreased in the residual mantle. This leads to the isotopic correlation in mantle-derived rocks plotted in Figure 4(a). The construction is similar to that used in Figure 2, but D values have been adjusted slightly for greater clarity.

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