Skip to content

Provenance of Deformed Olivine in Kīlauea's Summit and Lower East Rift Zone Eruptions.

Christina Cauley1, Paul Wallace1, Penny Wieser2, Kendra J. Lynn3, Allan Lerner4, Thomas Shea5

  • Affiliations: 1Dept. of Earth Sciences, University of Oregon, Eugene OR 97403; 2Dept. of Earth & Planetary Science, UC Berkeley, Berkeley, CA 94720; 3USGS Hawaiian Volcano Observatory, Hilo, HI 96720; 4Cascades Volcano Observatory, Vancouver, WA 98683; 5Dept. of Earth Sciences, University of Hawai\'i at Mānoa, Honolulu, HI 96822

  • Presentation type: Talk

  • Presentation time: Thursday 14:30 - 14:45, Room S150

  • Programme No: 1.9.2

  • Theme 1 > Session 9

Abstract

Deformed olivine in Kīlauea's summit and flank eruptions reveal re-entrainment from cumulate piles and complex magma pathways beneath the summit and East Rift Zone (ERZ). This study investigates cumulate and magma transport by analyzing olivine deformation in the 1960 Kapoho (68 crystals) and 2018 Ahuʻailāʻau (fissure 8; 174 crystals) eruptions, both on the lower ERZ, and six primarily juvenile Keanakākoʻi Tephra units (~1500--1800s CE; 423 crystals). Using electron backscatter diffraction (EBSD), olivines were classified as non-distorted, distorted, or deformed (mosaic textured or kink banded). Results reveal that 51% of Kapoho 1960 olivine show plastic deformation compared to only 12% of 2018 olivine. Larger grains ( 1 mm²) are more commonly deformed. Deformed crystals are generally primitive (Fo85-90), whereas undeformed olivines span a wide Fo range (Fo80-90), with low-Fo compositions approaching equilibrium with carrier melts. This pattern is similar to many upper ERZ and Southwest Rift Zone (SWRZ) eruptions (Wieser et al., 2020), but the lack of large crystals makes 2018 distinct. Fewer deformed crystals among the 2018 olivine are consistent with published evidence for shallow crystallization. In contrast, the 1960 Kapoho lavas contain a higher proportion of deeply crystallized olivine, extending to 12 km depth (Moore et al., 2015), and have abundant large, deformed crystals. Keanakākoʻi tephra contains 22--36% deformed olivine. The olivine size, composition, and basic deformation patterns for most Keanakākoʻi units are similar to those of modern upper ERZ and SWRZ eruptions despite evidence for lower magma fluxes and more poorly integrated magma bodies during the Keanakākoʻi period.