Intellectual Merit. Kilauea, on the island of Hawaii, is one of the most active and best-monitored volcanoes in the world. Its high magma supply rate and well delineated magmatic plumbing system make Kilauea an ideal venue for addressing fundamental questions about basaltic magma genesis. Its lavas provide essential petrologic and geochemical clues for delineating the nature of compositional heterogeneity within the Hawaiian plume and for assessing magma generation processes that cannot be readily ascertained by other methods. The PIs previously documented systematic short- and moderate-term (decades to centuries) geochemical variations within Kilauea's recent lavas. Over several centuries, Kilauea summit lavas record cyclic geochemical trends that correlate with volcanic processes such as eruption rates (more depleted sources appear to have undergone lower degrees of melting and produced less magma). To continue this work, a three-pronged approach is proposed combining field work with petrography, mineral chemistry, whole-rock major element and trace element abundances, and O, Pb, Sr, and Nd isotope ratios to assess the mantle causes (source and process) for compositional variation in Kilauea lavas. Part 1 involves continued monitoring of the geochemical evolution of the Puu Oo eruption, which has shown remarkable compositional variation related to crustal and mantle processes. Changing lava compositions provide new insights into magmatic processes. Part 2 examines the AD 900 to 1400 Uwekahuna Bluff lava section on the northwestern wall of the Kilauea's caldera. This study will allow evaluation of apparently cyclic geochemical variations at Kilauea on a few century time scale, and elucidate distribution of small-scale heterogeneities and the dynamics of mantle melting within the Hawaiian plume. Part 3 utilizes electron microprobe, LA-ICPMS, O isotope laser mass spectrometry and SHRIMP ionprobe to study olivine-hosted melt inclusions in high forsterite olivines (>86%) from selected Kilauea historical summit lavas. Preliminary work on these inclusions shows tremendous compositional diversity within individual lavas that may be related to the relatively short residence of magma in the summit reservoir (30-100 years). Major- and trace-element abundances, and O and Pb isotope ratios will be determined in these inclusions to better constrain the mantle heterogeneities and melting processes within the Hawaiian plume.
Broader Impacts. Broader impacts of this research include (1) developing teaching modules for undergraduate and graduate petrology classes using the results from our Kilauea research to highlighting magmatic processes at an active volcano and emphasing cooperative learning and development of higher order thinking skills, (2) mentoring graduate and undergraduate students, (3) giving public lectures to school groups and the local community, (4) gaining a better understanding of volcanoes that can negatively influence the quality of life, and (5) increasing international and national scientific cooperation through collaboration and utilization of multiuser facilities.
Overview. This project has just completed its final year, which was an extension, of our study of the eruptive products of Kilauea Volcano. We have worked closely with scientists at the US Geological Survey’s Hawaiian Volcano Observatory on lavas and tephra from the ongoing eruptions at the summit of the volcano and on its east rift zone at the Puu Oo vent. Intelluctural Merit. Several scientific products were produced and in progress nearing completion. One paper was published last year in a peer-reviewed scientific journal and two papers are in progress to be submitted by July, 2012. One new paper will detail the interaction of historical (1790-present) summit and rift zone magmas at Kilauea. This is the first study to document the temporal evolution of rift zone magmas and show their geochemical relationship to summit erupted lavas. This work demonstrates the close connection between these parts of the volcano’s magmatic plumbing system. However, we also show that some magmas bypass the summit reservoir and erupt in the rift zone first. The other new paper examines the fine isotope geochemistry of lavas from the Puu Oo rift eruption documenting dramatic short term variations (months to years) in isotopic chemistry. The variations in trace element and Pb, Sr and Nd isotopic ratios illustrate that the source of Kilauea is heterogeneous on a small scale (10’s to 100’s m) and that new magma with evolving composition is being continuously supplied to the volcano. Two abstracts were presented by students on this work at the American Geophysical Union’s Fall 2011 meeting in San Francisco in Dec. 2011. The Principal Investigator presented an invited talk at the same meeting discussing how olivine composition can help explain magmatic processes at Kilauea volcano. Broader Impacts. Two students, two post-doctoral scholars and the Principal Investigator were supported by this grant during the last year. Both post-doctoral scholars have recently started new scientific positions based on their work on this project. A teaching module for college-level petrology classes was further refined with reviews by users of the lab and our experience with the module. The modules is freely available to the community at the Carlton College website http://serc.carleton.edu/NAGTWorkshops/petrology/teaching_examples/35081.html.
