DUPAL anomaly

Castillo P. (1988) The DUPAL anomaly as a trace of the upwelling lower mantle. Nature 366, 667-670. 

Fig. 7. Location of high-(i and low-(i Archaean cratons with respect to CFB provinces and present-day DUPAL anomalies. Contour lines for DUPAL anomalies represent equal A7/4 values (Hart 1984). pi values for CFB provinces are calculated from Pb isotopic ratios (Carlson 1984 EUam Cox 1989 Hergt el al. 1989, 1991 Sharma et al. 1992 Wooden et al. 1993 Thirlwall et al. 1994 Molzhan et al. 1996 Antonini et al. 1999).

Hart, S. R. 1984. The DUPAL anomaly a large scale isotopic mantle anomaly in the Southern Hemisphere. Nature, 309, 753-757. 

Figure 24. Comparison of 5 0 values for NMORB and back-arc-basin glasses with Sr/ Sr ratios measured on the same samples data from Eiler et al. (2000a,b). Indian MORE have been excluded in order to avoid confounding effects of the Dupal anomaly, which is marked by large differences in Sr isotope ratios between Indian MORBs and other MORBs and appears to have no signature in 5 0 (Fig. 10).

The Pi values in different areas appear to have persisted for long periods of time, and there are currently spatial links with the locations of certain Mesozoic CFB and with oceanic basalts with DUPAL isotope signatures. Such long-lived U/Pb variations may therefore correspond to large-scale mantle anomalies, perhaps at relatively shallow levels in the mantle. 

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