Rare Earth Contribution to the Origin of Hawaiian Lavas

Rare earth abundances were determined by neutron activation in twenty Hawaiian lavas and one diabase of known chemical and mineralogical compositions. These results demonstrate a systematic relationship between the absolute or relative rare earth abundances and the petroehemistry of these rocks. Three distinct lava groups are recognized. These correspond to: (1) tholeiites, (2) alkali series, (3) nepheline-melilite basalts. Based on rare earths: a) The hawaiites and mugearite of the alkali series represent residual melts derived from alkali olivine basalts, most likely by fractional crystallization; the traehyte, however, seems to have a more complicated history, b) Fractional crystallization models linking nephelinites or alkali olivine basalts to tholeiites are possible. However, production of these three lava groups, independently, by various degrees of partial melting of the mantle is equally likely and cannot be distinguished from these fractional crystallization models, c) Daly limestone syntexis hypothesis to produce the nephelinites is unlikely.