Mineral equilibria, geothermometers and geobarometers in some Icelandic hyaloclastites

Abstract

Distribution coefficients between crystal and magma can be used to establish various properties of magmas. A number of natural hyaloclastites have been used to evaluate some of the established geothermometers and geobarometers. Comparison with experimental data on the same rocks shows that the olivine geothermometer gives the most reasonable results and in some cases plagioclase geothermometer can also be useful. However before mineral-liquid combinations can be used to evaluate magma properties equilibrium between the various phases must be established. This is not always simple and more experimental data is needed.

Contribution to the Fe₂O₃/FeO determination in basaltic rocks

“…This QFM-buffer equation is discussed by Eugster and Wones (1962). In the light of primary oxidation the liquidus temperature required for the fugasity equation can be calculated using the experimental data of several authors for Experiments: Yoder andTilley (1962), Carmichael (1967), Eggler (1971), Heiz (1976), Mäkipää (1978) and Steinthorsson (unpub. )…”