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An oscillatory rheology measurement of crystal-bearing molten magma

Atsuko Namiki 1, Konan Saito1, Satoshi Okumura2, Masato Hoshino3, Kentaro Uesugi3, Kazuhiro Tsukada4, Natsuko Takagi4, Michael Manga6

  • Affiliations: 1Graduate School of Environmental Studies, Nagoya University, Nagoya, Japan; 2Department of Earth Science, Tohoku University, Sendai, Japan; 3Japan Synchrotron Radiation Research Institute, Hyogo, Japan; 4Nagoya University Museum, Nagoya, Japan; 5Technical Center, Nagoya University, Nagoya, Japan; 6Department of Earth and Planetary Science, University of California, Berkeley, USA 

  • Presentation type: Poster

  • Presentation time: Monday 16:30 - 18:30, Room Poster Hall

  • Poster Board Number: 203

  • Programme No: 3.6.9

  • Theme 3 > Session 6

Abstract

The rheology of magma determines the ease of magma movement, which governs the possibility and style of eruption. Rheology includes both the viscous and elastic components of deformation. The viscosity of magma has been measured, but there are limited measurements of rheology. Oscillatory rheology measurements, imposing the sinusoidal strain and measuring the stress and its phase shift simultaneously, provide viscosity, elastic modulus, and their ratio. Further, magmas with temperatures below the liquidus have crystals, and the jamming framework of crystals may create complex rheology, as commonly observed in dense suspensions. Here, we conduct oscillatory rheology measurements of crystal-bearing high-temperature magma with a basaltic-andesite composition. Our measurements show that the magmas with a crystallinity of around 50 vol.% have solid-like behaviors and transition to liquid-like when the strain amplitudes become large enough. Silicic magmas are Maxwell fluids and show elasticity under rapid strain rates, which is different from our samples with a low-viscosity melt phase. In addition, the measured elastic modulus in our measurements is lower than that of the silicic melt measured at high frequencies. These results suggest that the jamming network of crystals generates the elasticity of the partially molten magma.