Constraint on the time scale of biotite-grade metamorphism during Acadian Orogeny from a natural garnet-garnet diffusion couple

Other| October 01, 1996 Constraint on the time scale of biotite-grade metamorphism during Acadian Orogeny from a natural garnet-garnet diffusion couple Jibamitra Ganguly; Jibamitra Ganguly University of Arizona, Department of Geosciences, Tucson, AZ, United States Search for other works by this author on: GSW Google Scholar Sumit Chakraborty; Sumit Chakraborty Universitaet zu Koeln, Federal Republic of Germany Search for other works by this author on: GSW Google Scholar Thomas G. Sharp; Thomas G. Sharp Universitaet Bayreuth, Federal Republic of Germany Search for other works by this author on: GSW Google Scholar Douglas Rumble Douglas Rumble Carnegie Institution of Washington, United States Search for other works by this author on: GSW Google Scholar Author and Article Information Jibamitra Ganguly University of Arizona, Department of Geosciences, Tucson, AZ, United States Sumit Chakraborty Universitaet zu Koeln, Federal Republic of Germany Thomas G. Sharp Universitaet Bayreuth, Federal Republic of Germany Douglas Rumble Carnegie Institution of Washington, United States Publisher: Mineralogical Society of America First Online: 02 Mar 2017 Online ISSN: 1945-3027 Print ISSN: 0003-004X Copyright © 1977 by the Mineralogical Society of America American Mineralogist (1996) 81 (9-10): 1208–1216. https://doi.org/10.2138/am-1996-9-1019 Article history First Online: 02 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn Email Permissions Search Site Citation Jibamitra Ganguly, Sumit Chakraborty, Thomas G. Sharp, Douglas Rumble; Constraint on the time scale of biotite-grade metamorphism during Acadian Orogeny from a natural garnet-garnet diffusion couple. American Mineralogist 1996;; 81 (9-10): 1208–1216. doi: https://doi.org/10.2138/am-1996-9-1019 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 SocietyAmerican Mineralogist Search Advanced Search Abstract We have determined the concentration profiles across the interface of a natural gametgamet couple in a biotite-grade rock from eastern Vermont. The couple consists of a grossular-spessartine garnet that had formed during regional metamorphism associated with the Acadian orogeny on an almandine core, which had crystallized during an earlier episode of metamorphism related to the intrusion of Fairlee granite at 411 ± 5 Ma. The concentration profiles were measured by both electron microprobe and analytical transmission electron microscope, and they were modeled to retrieve the value of ∫D(t)dt through the time that diffusion was effective but without recourse to any diffusion data.The length of the concentration profiles measured in microprobe is barely resolvable from that resulting from a convolution effect from the spatial averaging in the spot analyses. Deconvolution of the microprobe profiles yields a value of ∫D(t)dt = 0−3.4 × 10−11 cm2, suggesting very little or no diffusion. TEM analyses of the concentration profiles, which are not subject to any significant convolution effect, show a very small but definitive diffusion zone across the interface of the gamet-gamet couple, which yields a value of ∫D(t)dt = 7.6 × 10−12 cm2. Because D is a function of time through its dependence on temperature, this value of ∫D(t)dt provides an important constraint on the thermal history during the regional metamorphism. As an example, we used it in conjunction with the available diffusion data for garnet to derive ∼ 40-50 Ma as the probable time scale for the biotite-grade metamorphism, taking into account the effects of the off-diagonal terms and thermodynamic nonideality on the diffusion process. 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.