Role of porosity and dehydration reaction on the deformation of hot-pressed serpentinite aggregates

• Published in: Journal of the Geological Society Vol. 165; no. 3; pp. 639 - 649
• Main Authors: Arkwright, J. C, Rutter, E. H, Brodie, K. H, Llana-Fúnez, S
• Format: Journal Article
• Language: English
• Published: London Geological Society of London 01-05-2008; The Geological Society of London; Geological Society; Geological Society Publishing House
• Subjects: Alloys; brittle deformation; Changes; Crystalline rocks; deformation; dehydration; Earth sciences; Earth, ocean, space; Electron microscopes; Exact sciences and technology; experimental studies; failures; Geology; Grain growth; Grain size; igneous and metamorphic rocks; Igneous and metamorphic rocks petrology, volcanic processes, magmas; lizardite; Mechanical properties; metaigneous rocks; metamorphic rocks; metasomatic rocks; microstructure; nesosilicates; olivine; olivine group; orthosilicates; Petrology; Plastic deformation; Point defects; pore pressure; pore water; porosity; pressure; serpentine group; serpentinite; sheet silicates; silicates; strain; Strain hardening; Strain rate; strength; stress; Structural geology; talc; temperature; volume; strain rates; serpentinite; fine-grained materials; pore fluid; water pressure; olivine; aggregate; rupture; talc; pore water; sheet silicates; silicates; dehydration; flow; strain; nesosilicates; metaigneous rocks; porosity; lizardite; metamorphic rocks; high pressure; lead; grains; serpentine; collapse
• ISSN: 0016-7649; 2041-479X
• DOI: 10.1144/0016-76492007-119

Experimental deformation of hot-pressed powders of lizardite serpentinite was carried out to study the effect of the dehydration reaction to olivine+talc+water under controlled pore water pressure. Use of a porous aggregate ensured free movement of pore fluid into or out of the specimen in response to volume changes. The dehydration reaction further increases the porosity of the sample, causing weakening, but progressive pore collapse leads to strain hardening. At low strain rates, a transition to linear-viscous flow was inferred to be caused by the formation of transiently fine-grained olivine in the dehydration reaction. The inability of the rock to support high loads during dehydration at low strain rates means that the production of high-pressure water by dehydration and its subsequent expulsion will favour seismogenic failure in the surrounding rocks not directly involved in the dehydration reaction, rather than the serpentinite itself.