PETROLOGIC INSIGHTS INTO RIFT ZONE MAGMATIC INTERACTIONS UNDER KILAUEA′S NAPAU CRATER (1963-2011)

The high frequency of historical eruptions at Kilauea volcano presents an exceptional opportunity to address fundamental questions related to the source, storage, and transport of magmas in rift zones of active volcanoes. The Napau Crater area on Kilauea’s East Rift Zone (ERZ) is an excellent location to examine rift zone processes; no region on any other Hawaiian rift zone has experienced such frequent historical eruptions (seven eruptions within 50 years). Lavas from these eruptions may have resulted from a complex combination of crystal fractionation and multi-generational magma mixing. This study examined the whole-rock, glass, and mineral compositions of a suite of historical eruptions (1963-2011) from the Napau Crater area to characterize their petrologic relations. These data are used to elucidate the pre-eruptive history and temporal evolution of lavas from Napau Crater’s most recent episode, the March 2011 Kamoamoa eruption. Magmas from the 1963-1997 eruptions may have been left over within the rift zone and potentially available as mixing components for the 2011 eruption. Differentiation processes (e.g. mixing, crystal fractionation) associated with the Kamoamoa eruption are described by evaluating its geochemistry, resulting in a better understanding of the magmatic histories of rift zone lavas. The repeated nature of intrusions and eruptions in this region, and the geochemical signature of its lavas suggest that the Napau Crater area serves as an important magma mixing depot within the ERZ. Insights from these eruptions are integral for understanding if and how magmas interact within rift zones at basaltic volcanoes.