Mantle processes related to the explosive-effusive transition during the last eruptive cycle at Kilauea (Hawaii)

Understanding magma genesis and the evolution of intensive (temperature, pressure) and extensive (composition, degree of melting) parameters in the mantle source underneath highly active volcanic systems like Kilauea (Hawaii) is crucial for interpreting magma supply changes over time and helps recognize future volcanic hazards. Major and trace-elements in olivine are now commonly used to study variations in mantle lithologies and other processes affecting the mantle. Using this approach, we track the temporal evolution of primary melts through the most recent cycle of explosive and effusive eruptive styles, which spans the past 500 years. We report datasets of major and trace element in olivine from a low magma supply explosive period (1500-early 1820s Keanakakoi Tephra) and from a high magma supply effusive period (2018 LERZ, 2015-2018 Puuoo, 2008-2018 lava lake and 2020 eruptions in Halemaumau). Sc concentrations in olivine suggest that magma feeding the long-lived Puuoo cone (2015-2018) did not significantly interact with summit reservoir magma that ultimately erupted in the LERZ in 2018. Instead, the magma feeding Puuoo may have remained stored in the shallow middle East Rift Zone after Puuoo collapse on April 30, 2018. Sc, Mn, Co concentrations and Ni/Mg ratio in high forsterite (Fo >87) olivine advocate for an increase in the proportion of clinopyroxene in the mantle source (associated with a higher degree of partial melting) between the Keanakakoi Tephra period to 2018. The change in the primitive melt composition and increased degree of mantle melting potentially modulates the transition between explosive and effusive style periods at Kilauea. Analyzing these trace elements in olivine from future Kilauea eruptions could therefore provide important clues on subtle changes occurring at the mantle level, and help monitor whether the effusive-to-explosive period transition is also marked by geochemical changes.