Diffusion Flow Laws in Metamorphic Rocks

Abstract

Research Article| August 01, 1973 Diffusion Flow Laws in Metamorphic Rocks DAVID ELLIOTT DAVID ELLIOTT 1Department of Earth and Planetary Sciences, The Johns Hopkins University, Baltimore, Maryland 21218 Search for other works by this author on: GSW Google Scholar Author and Article Information DAVID ELLIOTT 1Department of Earth and Planetary Sciences, The Johns Hopkins University, Baltimore, Maryland 21218 Publisher: Geological Society of America First Online: 01 Jun 2017 Online ISSN: 1943-2674 Print ISSN: 0016-7606 Geological Society of America GSA Bulletin (1973) 84 (8): 2645–2664. https://doi.org/10.1130/0016-7606(1973)84<2645:DFLIMR>2.0.CO;2 Article history First Online: 01 Jun 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn Email Permissions Search Site Citation DAVID ELLIOTT; Diffusion Flow Laws in Metamorphic Rocks. GSA Bulletin 1973;; 84 (8): 2645–2664. doi: https://doi.org/10.1130/0016-7606(1973)84<2645:DFLIMR>2.0.CO;2 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGSA Bulletin Search Advanced Search Abstract Rocks which deform by pressure solution obey a diffusion flow law with a linear viscous or Newtonian stress to strain-rate relation. Undeformed relics of original grains preserved within newly grown crystals at grain boundaries under tension and presolved surfaces, together with accumulation of inert particles at grain boundaries under compression, are diagnostic evidence of a diffusion flow law. At a given stress, strain-rate is inversely proportional to the grain size to a power of two or three. A geologically useful plot has inverse temperature versus the logarithm of grain size as coordinates. Such a graph is separated into fields by three boundaries which meet at a triple point; within each field, either lattice diffusion, grain-boundary diffusion, or a dislocation flow law is predominant. It may be possible to calibrate this graph from naturally deformed rocks. Photomicrographs of isoclinally folded greenschist-grade quartzites and rhyolitic flows from the South Mountain–Blue Ridge area in Maryland demonstrate a diffusive mass transfer deformation mechanism, but estimates of effective diffusion coefficient compared to currently available laboratory diffusion data are insufficient to identify the diffusion path with certainty. However, the comparatively low ratio of metamorphic temperature to melting temperature and the physical nature of grain boundaries in metamorphic rocks, particularly concentrations of low-density impurities at grain boundaries, suggest the grain-boundary diffusion flow law. This content is PDF only. Please click on the PDF icon to access. First Page Preview Close Modal You do not have access to this content, please speak to your institutional administrator if you feel you should have access.