Rapid solid-state sintering in volcanic systems

• Published in: The American mineralogist Vol. 103; no. 12; pp. 2028 - 2031
• Main Authors: Ryan, Amy G, Russell, James K, Heap, Michael J
• Format: Journal Article
• Language: English
• Published: Washington Mineralogical Society of America 01.12.2018; Walter de Gruyter GmbH
• Subjects: Cascade Range; Crystal structure; Crystallinity; dacites; Densification; Diffusion; Earth Sciences; electron microscopy data; experimental studies; Experiments; felsic composition; Fluid flow; fluid phase; Geophysics; Grain boundaries; Hot isostatic pressing; igneous and metamorphic rocks; igneous rocks; Lava; Magma; modeling; Mount Saint Helens; Mount St. Helens; Permeability; Petrology; physical models; Porosity; pressure; Sciences of the Universe; SEM data; Sintering; Sintering (powder metallurgy); Skamania County Washington; solid phase; Solid state; Time dependence; United States; volcanic features; volcanic rocks; volcanism; Washington
• ISSN: 0003-004X; 1945-3027
• DOI: 10.2138/am-2018-6714

Solid-state sintering is a process wherein atomic diffusion along grain boundaries converts unconsolidated, crystalline aggregates into dense composites. It is a process that has largely been overlooked as significant to volcanic systems. Here, we present a preliminary suite of hot isostatic pressing experiments performed on naturally occurring crystalline dacite powders that demonstrate the efficacy of solid-state sintering at elevated pressures (40, 70 MPa) and temperatures (700-900°C) over short timescales (2.5 days). The experimental products are dense, low-permeability rocks, supporting the hypothesis that solid-state sintering may be an important process that acts on timescales relevant to magma rise and eruption. We use the experimental data to constrain a preliminary model for the extent of densification as a function of temperature, confining pressure and time. Last, we present sintering maps relevant to the time-dependent loss of porosity and permeability in granular volcanic materials. Solid-state sintering is a densification process with the capacity to heal fluid-flow pathways in volcanic systems within months to years.