We found a match
Your institution may have rights to this item. Sign in to continue.
- Title
High‐Temperature Fracture Growth by Constrained Sintering of Jadeite and Quartz Aggregates.
- Authors
Doungkaew, Natchanan; Eichhubl, Peter
- Abstract
Fractures control heat and mass transfer and rheology in a wide range of subsurface regimes, ranging from low‐temperature diagenetic environments to high‐temperature metamorphic and magmatic systems. To investigate processes of opening‐mode fracture growth at high homologous temperature, we conducted constrained high‐temperature sintering experiments of thin layers of porous jadeite and quartz aggregate attached to a non‐sintering mullite substrate. Samples were heated stepwise at a low rate in a muffle furnace from 25°C to 1,000°C under ambient air pressure and examined for changes in mineral composition, texture, porosity, and fracture morphology using powder‐X‐ray diffraction, macro‐photography, reflected incident light microscopy, and secondary electron microscopy. Mineral reactions in the jadeite and quartz sample layer include jadeite and quartz reacting to albite at 600°C and the formation of nepheline and orthoclase at 900°C and 1,000°C. Opening‐mode fractures are first observed at 850°C coincident with the first presence of a melt phase with low aperture‐to‐length ratios similar to elastic‐brittle fractures. At 900°C, melt becomes increasingly abundant, and fractures obtain ductile morphology with high aperture‐to length ratios and blunted tips resulting from fracture growth by growth and coalescence of larger pores at the expense of smaller pores. In the absence of an externally applied mechanical load, we conclude that fracture growth is driven primarily by sintering stress resulting from differential contraction between sample layer and substrate associated with high‐temperature mineral reactions, melt formation and redistribution, and changes in pore structure. Similar fracture processes may be relevant to the segregation and migration of melt in magmatic systems. Plain Language Summary: Natural fractures provide important pathways for the migration of fluids and heat in the Earth. The formation of fractures is generally understood as a brittle failure process. At temperatures that approach or exceed melting conditions of rock, the formation of fractures deviates from the brittle failure processes found at shallower and cooler conditions. We investigated fracture growth under such partial melting conditions by sintering thin layers of the minerals jadeite and quartz on wafers of temperature‐resistant mullite in a furnace at temperatures of up to 1,000°C. Upon heating to 850°C, fractures form in the jadeite and quartz layer in the presence of a partial melt by contraction of the initially porous mineral aggregate. With wide apertures and blunted tips, these fractures differ in shape from brittle fractures, reflecting fracture morphologies observed in rocks that have undergone high‐temperature deformation in the deep geologic subsurface. Key Points: Opening‐mode fractures are observed to form during constrained liquid sintering of aggregates of jadeite and quartz at 850 to 1,000°CFractures are characterized by wide aperture to length ratios and blunt tips consistent with ductile fracture growthFractures are inferred to grow by tensile sintering stress induced by melt redistribution and changes in pore structure
- Subjects
MECHANICAL loads; POROSITY; ROCK deformation; BRITTLE fractures; SINTERING; DUCTILE fractures; QUARTZ
- Publication
Journal of Geophysical Research. Solid Earth, 2023, Vol 128, Issue 4, p1
- ISSN
2169-9313
- Publication type
Article
- DOI
10.1029/2022JB025565