Petrology and eruption styles of Kickʹem-Jenny submarine volcano, Lesser Antilles island arc

Basaltic magmas erupted from the Kickʹem-Jenny submarine volcano have assimilated amphibole-bearing crustal material. The MgO content of the basalts ranges from ~12 to ~4 wt.%, and some of the more evolved members of the suite may have eventually become saturated with amphibole as well as olivine, plagioclase, clinopyroxene, and titanomagnetite. Major-element and trace-element compositions are consistent with processes dominated by assimilation-fractional crystallization. Analysis of glassy melt inclusions (MgO ~2.9 wt.%) in olivine phenocrysts suggests that pre-eruption melt water contents may have been as high as ~5 wt.%. Glass compositions are interpreted to reflect eruption-related loss of water. sible observations and dredge sampling of the volcano have revealed two styles of eruption: explosive, tephra-producing eruptions, and non-explosive, dome-forming lava eruptions. The contrasting styles of eruption are thought to be due principally to the rate and extent of eruption-related degassing of ≤ 5 wt.% juvenile H2O, although magma interactions with external water may also play a role in explosive eruptions.