A statistical test of the two reservoir model for helium isotopes

A common hypothesis is that helium isotopes in mantle-derived materials rep resent two distinct populations. the midocean ridge (MORB) reservoir and th e oceanic island (OIB) reservoir. We ask the question 'Can we disprove the null hypothesis that OIB and MORB samples are drawn from the same populatio n distribution function?' The answer is no, meaning that the datasets could be drawn from the same population. Previous studies have reached the oppos ite conclusion by comparing extreme values in one population with the mean value, or range, of the other population after the extreme values are remov ed, The variance of the He-3/He-4 distribution for various ridge segments d ecreases with the spreading rate and the high variance of individual OIB da tasets is consistent with slow spreading, small sampled volume, or low degr ees of melting or degassing. (C) 2001 Elsevier Science B.V. All rights rese rved.