Intellectual Merit. Kilauea volcano is the premier location to study basaltic magmatic processes. It is one of the best monitored and most active volcanoes in the world. Field, petrologic, geochemical, and geophysical studies have delineated its basic magmatic plumbing system from the mantle source to the surface. Modern and ancient Kilauea lavas provide essential clues for deciphering the nature of compositional heterogeneity within the Hawaiian mantle plume and for assessing processes of magma generation, transport and storage. Previous studies of historical and prehistoric Kilauea summit lavas documented cyclic geochemical variations on a time scale of decades to centuries. Historically, these compositional variations correlate with factors such as eruption rate (more depleted sources appear to have undergone lower degrees of melting and produced less magma) and rare, explosive eruptions (e.g., 1924). Detailed investigation of the ongoing, 28-year-old, voluminous (>3 km3) Pu?u O?o eruption has revealed shorter-term trends in lava chemistry (years) that may be controlled by the melting of small-scale compositional heterogeneities within the Hawaiian plume, including recently depleted and Mauna Loa-like sources. Currently, Kilauea has two active eruptions: Pu`u O?o (1983-present) on its east rift zone and a new eruption at the volcano?s summit, Halema?uma?u (2008-present).
A three-part study is proposed involving petrography, mineral chemistry, whole-rock major and trace element abundances, and Pb, Sr, Nd and O isotope ratios to investigate past, present and future compositional variations in Kilauea lavas. Present and future variations: will involve two time series experiments using lavas from the current Pu`u O?o and Halema?uma?u eruptions. First, time-series petrologic and geochemical monitoring will document changes in eruptive behavior and/or lava chemistry. After assessing the effects of crustal processes (e.g., crystal fractionation and/or magma mixing), these data will allow evaluation of mantle processes. Second, the chemistry of juvenile glassy tephra from the Halema?uma?u summit eruption will be compared with contemporaneous Pu`u O?o rift zone lavas, and geophysical and other data collected by the USGS Hawaiian Volcano Observatory, to better delineate the architecture of Kilauea?s magmatic plumbing system. Sustained eruptions at two distant vent locations (summit and rift zone) provide opportunity to track the movement of magma through the volcano?s plumbing system as a function of time and space using lava chemistry. This work will have implications for other basaltic volcanoes. Third, the last 200+ ka of Kilauea?s evolution will be assessed using lavas from the ~1.7- and 2.0-km long, continuously cored Scientific Observation Hole (SOH) drill holes. The (SOH) core represents the poorly studied early shield stage of a Hawaiian volcano, which was not sampled by the Hawaii Scientific Drilling Project (HSDP) at Mauna Kea volcano. To better constrain ages for SOH core samples it is proposed to obtain high precision 40Ar-39Ar ages for 14 samples. The results will be used to model Kilauea?s volcanic growth rate and temporal geochemical evolution. The chemistry of coeval Kilauea (SOH, early shield stage) and Mauna Kea (HSDP, late shield stage) lavas will be compared to evaluate mantle source and melting conditions for lavas extracted contemporaneously from the eastern, Kea side of the Hawaiian plume.
Broader Impacts. The proposed research will involve (1) developing teaching modules for undergraduate and graduate courses using the results from our Kilauea research to highlight magmatic processes at an active volcano and emphasize cooperative learning and development of higher order thinking skills, (2) mentoring a post-doctoral researcher, and graduate and undergraduate students, (3) giving public lectures to school groups and the local community on the eruptions of Kilauea, (4) gaining a better understanding of volcanoes, which can adversely influence the quality of life, and (5) increasing international and national scientific cooperation through collaboration and utilization of facilities.