Isotope correlation diagrams

It is unlikely, however, that petrogenetic processes can be satisfactorily reduced to two dimensions, and this must be borne in mind when using two-dimensional projections (Ziiidler and Hart, 1986). In fact Zindler et ai (1982) proposed a three-dimensional Sr-Pb-Nd plot for oceanic basalts and showed that averaged data 

Three-dimensional plot of average Pb/ Pb, Nd/ Nd and Sr/ Sr for oceaidc basalts, indicating roherence of isotopic ratios (after Zindier et a/., 1982). 

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Figure 6. Three-isotope correlation diagram for Mg using S-notation fsee text) for unnormalized data from terrestrial samples and Mg-rich Allende minerals.

Nd/ Nd vs Sr/ Sr isotope correlation diagram, showing the main oceanic mantle reservoirs of Zindler and Hart (1986). DM, depleted mantle BE, bulk silicate Earth EMI and EMII, enriched mantle HIMU, mantle with high U/Pb lado PREMA, frequendy observed PREvalent MAnde composition. The Mantle array is defined by many oceanic basalts and a bulk Earth value for Sr/ Sr can be obtained from this trend. 

Many authors portray mixing on an Nd-Sr isotope correlation diagram following the principles oudined by DePaolo and Wasserburg (1979). For instance, McCulloch et al. (1983) use this diagram (Figure 6.22) to show how the... 

Consider, for example, one of the early observations drawn from isotope correlation diagrams. In Figure 6.10 the Nd-Sr compositions of the continental... 

Oxygen isotope — radiogenic Isotope correlation diagrams... 

Correlations between radiogenic and oxygen isotopes are of particular importance because variations in the two types of isotope come about through totally dlfTerent mechanisms. This means that correlation diagrams of this type convey information of quite a different type from either stable isotope correlation diagrams (Sections 7.3.3, 7,4.2) or radiogenic isotope correlation diagrams (Section 6.3.5). 

Recognizing Crustal rocks are enriched in both strontium and oxygen isotopes relative to the crustal contam- mantle (Figure 7.6) thus a bivariate Sr-0 isotope correlation diagram is a powerful ination in means of recognizing crustal contamination in mantle-derived rocks. There are two... 

The results in Table 12.6 indicate that sample 64.01 (Mt. Bumstead) yields a plateau date of 170.4 1.4 Ma which is statistically identical to 169.4 1.1 Ma derived from an Ar-isotope correlation diagram (Faure and Mensing 2005). These dates are more accurate and more precise than the conventional whole-rock K-Ar dates of 188.6 2.2 and 149.7 2.1 Ma of this sample. Two samples (64.10, Mt. Bumstead and 27.17, Storm Peak) did not form " ArT Ar plateaus, but the Ar-isotope ratios did define isochrons with dates of 167.5 3.8 and 161.8 8.6 Ma, respectively. Sample 27.46 (Storm Peak) produced a plateau-date of 129.0 5.0 and a 126 3.8 Ma isochron date both of which indicate major loss of " Ar consistent with the high abundance (85%) of devitrified matrix. 

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