Figure 24. A comparison of primordial and radiogenic He and Ne isotope abundances
in samples from Kola UACC, MORB and OIB.
While the
4He*/21Ne* production ratio is almost constant, this ratio and the ratio
between primordial species vary within a great range which can be approximated by a
straight line. Projection of the production ratio via the approximation line to the
primordial ratio indicates
3He/22 Ne similar to the actual solar value implying solar-
like 3He/22Ne in the mantle before the fractionation. Possible mechanisms
responsible for the fractionation are discussed in the text.