Rapid Temporal Geochemical and Isotopic Variations of Tephra From the Ongoing 2008 Summit Eruption of Kilauea Volcano, Hawaii

The 2008 summit eruption of Kilauea Volcano is its first summit eruption since 1982 and its first explosive eruption since 1924. Chemical and high-precision Pb isotopic analyses of eight samples of juvenile material from this eruption reveal rapid and systematic changes in magma composition from March 23 to April 14. Compared to the most recent lavas from the ongoing Puu Oo rift zone eruption, the earliest erupted 2008 summit tephra (March 23) has relatively high abundances and ratios of incompatible elements (e.g., K2O, TiO2 and Nb/Y). Most of these chemical parameters are similar to Kilauea summit lavas from the late 1960s to early 1970s. The exception is K2O, which is anomalously high (similar to summit lavas from the early 20th century). Subsequently erupted 2008 summit tephras have abundances and ratios of incompatible elements that are similar to recent Puu Oo lavas. The 206Pb/204Pb ratios of four 2008 summit tephras display a systematic temporal decrease from values intermediate between recent Puu Oo lavas and the September 1982 summit lava to values identical to recent Puu Oo lavas. Taken together, these observations suggest that the early 2008 summit tephra contains a component of magma that had been stored within Kilauea's summit reservoir since the late 20th century. However, this stored magma may have been contaminated within the crust to anomalously raise its K2O content.