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Published November 2013 | Supplemental Material + Published
Journal Article Open

Temporal geochemical variations in lavas from Kīlauea's Pu'u 'Ō'ō eruption (1983–2010): Cyclic variations from melting of source heterogeneities

Abstract

[1] Geochemical time series analysis of lavas from Kīlauea's ongoing Pu'u 'Ō'ō eruption chronicle mantle and crustal processes during a single, prolonged (1983 to present) magmatic event, which has shown nearly two-fold variation in lava effusion rates. Here we present an update of our ongoing monitoring of the geochemical variations of Pu'u 'Ō'ō lavas for the entire eruption through 2010. Oxygen isotope measurements on Pu'u 'Ō'ō lavas show a remarkable range (δ^(18)O values of 4.6–5.6‰), which are interpreted to reflect moderate levels of oxygen isotope exchange with or crustal contamination by hydrothermally altered Kīlauea lavas, probably in the shallow reservoir under the Pu'u 'Ō'ō vent. This process has not measurably affected ratios of radiogenic isotope or incompatible trace elements, which are thought to vary due to mantle-derived changes in the composition of the parental magma delivered to the volcano. High-precision Pb and Sr isotopic measurements were performed on lavas erupted at ∼6 month intervals since 1983 to provide insights about melting dynamics and the compositional structure of the Hawaiian plume. The new results show systematic variations of Pb and Sr isotope ratios that continued the long-term compositional trend for Kīlauea until ∼1990. Afterward, Pb isotope ratios show two cycles with ∼10 year periods, whereas the Sr isotope ratios continued to increase until ∼2003 and then shifted toward slightly less radiogenic values. The short-term periodicity of Pb isotope ratios may reflect melt extraction from mantle with a fine-scale pattern of repeating source heterogeneities or strands, which are about 1–3 km in diameter. Over the last 30 years, Pu'u 'Ō'ō lavas show 15% and 25% of the known isotopic variation for Kīlauea and Mauna Kea, respectively. This observation illustrates that the dominant time scale of mantle-derived compositional variation for Hawaiian lavas is years to decades.

Additional Information

© 2013 American Geophysical Union. Received 5 March 2013; Revised 9 September 2013; Accepted 7 October 2013; Published 15 November 2013. We thank Jane Barling, Bruno Kieffer, and Vivian Lai for their assistance with analyses at PCIGR at UBC, Kyle Tanguichi and Adonara Murek for sample preparation and curation at the University of Hawai'i, and J. M. Rhodes for XRF analyses at University of Massachusetts. Claude Maerschalk assisted with Pb and Sr column chemistry for a subset of samples. Daniel Heaton provided assistance with several isotope analyses at San Diego State University. We appreciate reviews by Julie Prytulak, Joel Baker, and Christoph Beier. This research was supported by grants from the National Science Foundation to M. Garcia (EAR11–18741) and A. Pietruszka (EAR11–18738). This paper is SOEST Contribution No. 8939.

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Additional details

Created:
August 22, 2023
Modified:
October 26, 2023