Crystallization and oxidation during emplacement of lava lobes
Lava emplacement induces numerous processes, among which are crystallization and oxidation. While crystallization is mainly thermally driven, oxidation may be primary, or secondary if an environmental interaction is involved. Here, three major processes are considered, crystallization, volume oxidation, and a surface alteration that may result in surface oxidation, which has heretofore not been described. All these processes are shown to be high-temperature phenomena and they are not related to weathering. The nature of these processes and their quantification is elucidated by isothermal heat treatment experiments of quenched lava samples. This quantification allows scientists to delineate the thermal history of basaltic melts in relation to their textures; oxidation is suggested to be a consequence of crystallization; surface alteration involves cation migration to lava surfaces in the presence of an oxygen gradient, resulting in surface oxidation if the migrating cation is iron.