Research Article| November 01, 1972 Flow Differentiation in Igneous Dikes and Sills: Profiles of Velocity and Phenocryst Concentration PAUL D KOMAR PAUL D KOMAR Department of Oceanography, Oregon State University, Corvallis, Oregon 97331 Search for other works by this author on: GSW Google Scholar GSA Bulletin (1972) 83 (11): 3443–3448. https://doi.org/10.1130/0016-7606(1972)83[3443:FDIIDA]2.0.CO;2 Article history received: 06 Mar 1972 first online: 02 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation PAUL D KOMAR; Flow Differentiation in Igneous Dikes and Sills: Profiles of Velocity and Phenocryst Concentration. GSA Bulletin 1972;; 83 (11): 3443–3448. doi: https://doi.org/10.1130/0016-7606(1972)83[3443:FDIIDA]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 Mechanical interactions between phenocrysts during magma flow give rise to a grain-dispersive pressure. During intrusion into a dike or sill, in the absence of forces other than those of grain interaction, the grain-dispersive pressure must be constant across the flow width. As a result, the concentration of phenocrysts must decrease toward the walls to offset the increase in the velocity gradient as the walls are approached. This mechanism has been offered as an explanation for the observed rapid but gradational increases in content from phenocryst-poor margins to a phenocryst-rich center, especially in picritic dikes and sills.A relation for the grain dispersive pressure is solved together with the momentum equation of fluid flow, utilizing an empirical relation for the apparent viscosity of the phenocryst suspension. Solutions for steady flow between parallel walls demonstrate pluglike velocity profiles as well as phenocryst-concentration increases toward the center away from the walls. The velocity is nearly the maximum value within the central half of the flow. Therefore very strong pseudoplastic non-Newtonian behavior of the magma need not be assumed to explain the observed phenocryst concentration variations. 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.
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Paul D. Komar (1972) studied this question.