Magnetic Petrology of Unzen Volcano, Japan: Implications for Lava Dome Oxidation Processes

Synopsis In order to understand the oxidation state in lava dome, magnetic petrological analyses were carried out on lava samples from the lava domes and block-and-ash-flow deposits of the 1990-1995 eruption of Unzen volcano, Japan. Samples from the surface of actual lava dome were highly oxi- dized, while those from the inner part were unoxidized. Samples from endogenous dome showed as almost the same oxidation states and processes as those from exogenous dome. This suggested that the different oxidation state is due to the difference of position of the samples in the lava dome rather than the difference of the growth style.