National Oceanic and
Atmospheric Administration
United States Department of Commerce


FY 2018

Chemical variations in the 1998, 2011, and 2015 lava flows from Axial Seamount, Juan de Fuca Ridge: Cooling during ascent, lateral transport, and flow

Clague, D.A., J.B. Paduan, B.M. Dreyer, W.W. Chadwick, Jr., K.R. Rubin, M.R. Perfit, and A.T. Fundis

Geochem. Geophys. Geosyst., 19(9), 2915–2933, doi: 10.1029/2018GC007708, View online (open access) (2018)

Lava flows erupted at Axial Seamount in 1998, 2011, and 2015 are chemically heterogeneous and display decreases in MgO content in their glass rinds with increasing distance from the summit. The trends are consistent with eruption temperature decreases down the rift zones of ~0.5 °C/km within 20 km of the caldera and ~0.9 °C/km at greater distance (only observed in the 2011 eruption). Cooling during magma transport in dikes is the likely cause of the temperature trends observed, related to the effects of cooler wall rocks in areas with less frequent dike intrusions. Flows also cooled as they advanced on the seafloor at rates 3–5 times greater than observed at Kilauea volcano in Hawaii for subaerial tube‐fed pahoehoe flows. Lavas erupted in and near the caldera in 1998 and 2011 are slightly enriched transitional mid‐ocean ridge basalt that are aphyric and have glass MgO content of 7.1–7.6 wt %. The 2015 lavas have similarly enriched incompatible element compositions typical of transitional mid‐ocean ridge basalt, but those erupted inside and on the northeast rim of the caldera contain higher glass MgO of 7.8–8.3 wt % and more abundant plagioclase phenocrysts typical of the normal mid‐ocean ridge basaltic lavas erupted between 1290 and 1370 CE. The brief recharge period between the 2011 and 2015 eruptions did not allow magma stored in the shallow reservoir to cool and degas as much as between prior eruptions since 1650 CE, suggesting that the most recent recharge period was shorter than the multicentennial average.

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