Melting and crystallization relations of the snake river basalts of Southern Idaho, USA

Abstract

The experimental melting and crystallization relations of some basalts of the Snake River Plain are investigated. They compromise two tholeitic series, those of the Snake River and those of the King Hill and Craters of the Moon. The fractionation of the first group involves dominantly crystallization of olivine and plagioclase, with pyroxene fractionation playing a minor role, in accord with its very late crystallization in the experimental melting. In the second group removal of iron-titanium oxides and apatite accompanies olivine and plagioclase extraction and leads to silica enrichment, with corresponding reduction in the rate of iron enrichment. Though a genetic link probably connects the two series its precise nature still remains to be disclosed. © 1970.