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Harnessing X-ray microtomography and 3D diffusion models to constrain magmatic timescales in complex crystals

Adrien J. Mourey1 , Euan J.F. Mutch1,2

  • Affiliations: 1Earth Observatory of Singapore, Nanyang Technological University, Singapore, Singapore  2Asian School of the Environment, Nanyang Technological University, Singapore, Singapore

  • Presentation type: Talk

  • Presentation time: Thursday 08:45 - 09:00, Room S150

  • Programme No: 1.1.2

  • Theme 1 > Session 1

Abstract

Magmatic minerals act as natural archives of the timescales of volcanic processes (e.g., fractional crystallization, mixing, degassing, and decompression rates). Part of the knowledge on the timescales of volcanic processes is retrieved from modeling diffusion gradients observed in minerals and melt. Most diffusion modeling studies use a one-dimensional model that does not account for diffusion from multiple directions or sectioning effects. In some rare cases, considerations of 3D diffusion were explored using ideal crystal shapes, but textural crystal complexities have yet to be properly accounted for. X-ray micro-tomography (X-μCT) scans offer the possibility to access the full morphological representation of the crystal and melt inclusions. We used this technique to create the first-ever real 3D diffusion model of natural olivine with its melt inclusions. Olivine grains are from the 1820 Keanakākoʻi golden pumice eruption at Kīlauea (Hawaiʻi) and display a wide range of textures (polyhedral to skeletal). By employing a sophisticated finite element 3D multiphase diffusion model, we modeled Fe-Mg and H diffusion in olivine and its melt inclusions to estimate mixing timescales, ascent-related cooling rates, and decompression rates. This innovative approach combining X-μCT and diffusion modeling can fully integrate crystal morphology and melt inclusion morphology to access more accurate diffusion timescales and decompression rates, without worrying about the location of the diffusion profile in a section. This technique not only promises to refine our understanding of diffusion timescales and decompression rates in volcanic systems but also opens new avenues for investigating other critical mineral phases in diffusion chronometry.