Features of crystallization of andesite melt at moderate hydrogen pressures (experimental study)

Important problems of magma differentiation, formation of native metals and ore formation processes in the earth's crust are increasingly associated with the active participation of hydrogen. In this paper, new experimental data on the crystallization of andesite melts at high temperatures (900–1250°C) and hydrogen pressures (10–100 MPa) have been obtained, which clarify the possible role of hydrogen in the processes occurring in andesite melts in the earthʼs crust and during volcanism under strongly reduced conditions (f(O2) = 10–17–10–18). In crystallization experiments, it was found that the crystal compositions (pyroxenes and plagioclases) formed in experiments on crystallization of andesite melt under hydrogen pressure closely correspond to the crystal compositions of lava flows of Avacha volcano in Kamchatka. This result can be considered as an experimental confirmation of the participation of hydrogen in the volcanic process.