Mantle and Crustal Causes of Compositional Variation in Kilauea Historical Lavas

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EAR-0001123GarciaLavas provide essential clues to the crustal and mantle processes associated with volcanoes. Kilauea Volcano is an ideal natural laboratory for evaluating how physical processes within volcanoes cause observable changes in lava composition and it is the best-studied volcano in the world. Thus, we can address fundamental problems from a well-constrained perspective. This project involves making precise trace element and isotope analyses for quantitative modeling of mantle melting processes, assessing source heterogeneity and evaluating crustal contamination effects on the composition of Kilauea historical lavas. We will make a comprehensive petrologic and geochemical characterization of historical Kilauea lavas, including lavas from the ongoing Puu Oo eruption. We have documented long-term, systematic isotopic and compositional variations within its historical summit lavas (~200 year period) and short-term geochemical variations during the ongoing (17+ years) Puu Oo rift zone eruption. The magma for the Puu Oo and other major rift zone eruptions is thought to have bypassed the summit reservoir and to give us a clearer picture of mantle melting processes and source heterogeneity. The cause for the lower oxygen isotope ratios in oceanic island basalts compared to mid-ocean ridge basalts remains controversial. Some studies have been related the differences to distinct mantle sources, while other studies have invoked crustal contamination. We documented evidence for extensive crustal contamination in some Kilauea historical lavas, including those from the Puu Oo eruption but have not determined the oxygen isotope value for Kilauea's source. New techniques will be use to determine oxygen isotopes for well characterized samples from the ongoing eruption, other historical lavas and hydrothermally altered rocks from a 3 km deep geothermal well to better understand mantle source heterogeneity and crustal contamination processes for Kilauea. The results of this project will allow us to: 1. evaluate the relative importance of mantle source heterogeneity and changes in extent of partial melting in controlling geochemical variation of historical Kilauea lavas; 2. determine the amount of crustal contamination in Kilauea lavas and better understand the oxygen isotope heterogeneity in its source; and 3. decipher the mantle melting processing associated with the ongoing Puu Oo eruption.