Some basaltic and andesitic gases

作者：Alfred T. Anderson Jr. · 发表于：Reviews of Geophysics · 年份：1975 · DOI：10.1029/rg013i001p00037 · 被引用次数：171 · 研究领域：Geological and Geochemical Analysis、earthquake and tectonic studies、High-pressure geophysics and materials

Igneous gases escape from igneous rocks and magmas. They may originate by effervescence or they may bubble through the melt from an external source. In this paper I review data (mostly post‐1963) on H2O, B, CO2, N2, O2, Ne, sulfur gases, Cl, Ar36, Ar40, Br, Kr, I, Xe, Hg, and Rn. The compositions of volcanic gases are compatible with solubility and melt composition for H2O, Cl, and possibly sulfur gases. For other gases there are either inadequate data or conflicting data (CO2). Volcanic gas emitted at surface pressure is generally very rich in H2O because H2O is the principal gas dissolved in most melts. CO2‐rich volcanic gases can be explained by separation of gas from melt at pressures of a few tens of atmospheres and by effervescence of magmas with high ratios of dissolved CO2/H2O (mostly alkaline basalts). There is no single magmatic gas phase. Glassy basalts from the sea floor have substantial concentrations of both active and noble gases. The concentrations of H2O and Cl correlate with the alkali concentration (especially K2O). The recorded concentrations of H2O and CO2 in sea floor basalts are far below saturation at 500 atm. Yet the basalts contain tiny vesicles. It appears likely that magmatic gas of basalts at sea floor pressure is 60% SO2, 20% H2O, 10% H2S, and 10% CO2 at 1200°C. The concentrations of Cl and H2O in basaltic and andesitic glasses trapped in large crystals in pumices from continental margins are about 10 times those of deep sea basalts. Detailed rel...