Olivine in four dimensions: a textural and chemical record of magmatic phenomena underneath Kīlauea Volcano (Hawai‘i)

Abstract

This dissertation addresses a wide range of research themes centered on understanding how olivinecrystals record magmatic histories. Using experimental, analytical methods, and computational modeling, we assess the textures and chemistry of a set of olivine crystals to answer outstanding yet fundamental questions within the field of petrology and volcanology: (1) How fast are natural olivine phenocrysts formed? (2) How long do olivine crystals preserve the compositional archive of a magma recharge? (3) Can we track long-term changes in the nature of primary melts at Kīlauea with major and trace elements in olivine? The chemical composition of olivine, its zoning patterns (chemical gradients in the crystals) and its textures are commonly used to investigate the evolution of magmas from their source to the Earth’s surface. Compositional zoning in olivine crystals is also a preserved, measurable record that provides constraints on timescales of magma mixing, and transport. This dissertation is composed of four chapters. The first chapter of this dissertation introduces the topics that are involved in the subsequent chapters. The second chapter is a study of the kinetics of olivine growth and the development of characteristic crystal morphologies using laboratory crystallization experiments on a Hawaiian basalt composition. Three-dimensional (3D) characterization is carried out to track the olivine crystallization process in the resulting experiments. A separate set of 3D scans of olivine crystals from an early 19th century Kīlauea eruption yields additional insights into crystal settling and the formation of crystal-rich layers at Kīlauea. In the third chapter, numerical diffusion models that use diffusion chronometry principles are used to determine how olivine phenocrysts preserve their compositional archives and record magmatic intrusions during the 2018 LERZ Kīlauea eruption. The fourth chapter of the dissertation investigates the mechanisms that control the transition from an effusive to an explosive style at Kīlauea using trace elements concentration in olivine. These studies change our perspectives of how olivine crystals should be used to understand the present and past volcanic activity in mafic systems like Kīlauea to better make predictions on future volcanic behavior.