fig19.htm

Figure 19. Ar-Ne isotope plot (after Marty et al., 1999). Notice relatively low 40Ar/36Ar ~3,000 ratio measured in a mantle "end-member'' together with the least contaminated Ne. This ratio is somewhat lower than the model-derived lower mantle values and much lower than values inferred from observation for the upper mantle, approx 40,000 (see Tolstikhin and Marty, 1998, and references therein). Extrapolation could lead to a somewhat higher value for the mantle source. However the extrapolation trends and even possibility of the extrapolation are not clear.


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