Single-crystal IR spectroscopy of pyrope-almandine garnets with minor amounts of Mn and Ca

Other| April 01, 1996 Single-crystal IR spectroscopy of pyrope-almandine garnets with minor amounts of Mn and Ca A. M. Hofmeister; A. M. Hofmeister Washington University, Department of Earth and Planetary Sciences, St. Louis, MO, United States Search for other works by this author on: GSW Google Scholar T. J. Fagan; T. J. Fagan Search for other works by this author on: GSW Google Scholar K. M. Campbell; K. M. Campbell Search for other works by this author on: GSW Google Scholar R. B. Schaal R. B. Schaal Search for other works by this author on: GSW Google Scholar Author and Article Information A. M. Hofmeister Washington University, Department of Earth and Planetary Sciences, St. Louis, MO, United States T. J. Fagan K. M. Campbell R. B. Schaal Publisher: Mineralogical Society of America First Online: 02 Mar 2017 Online Issn: 1945-3027 Print Issn: 0003-004X Copyright © 1996 by the Mineralogical Society of America American Mineralogist (1996) 81 (3-4): 418–429. https://doi.org/10.2138/am-1996-3-416 Article history 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 A. M. Hofmeister, T. J. Fagan, K. M. Campbell, R. B. Schaal; Single-crystal IR spectroscopy of pyrope-almandine garnets with minor amounts of Mn and Ca. American Mineralogist 1996;; 81 (3-4): 418–429. doi: https://doi.org/10.2138/am-1996-3-416 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 Mg2+-Fe2+ substitution in the dodecahedral interstice of eight natural single crystals and two synthetic polycrystalline garnets was investigated by measurement of mid- and far-infrared (IR) reflectance spectra across the pyrope-almandine [Py-Al = (Mgx-Fe1–x)3Al2Si3O12] binary. The effect of minor Mn and Ca substitution was investigated by comparison with spectra of four additional natural garnets, Py8Al82Sp10 and Py10Al76Sp14, where Sp denotes spessartine (Mn3Al2Si3O12), and Py72Al18Gr10 and Py54Al36Gr10, where Gr denotes grossular (Ca3Al2Si3O12). Data obtained from the two synthetic polycrystals are in excellent agreement with data from the single crystals. Frequencies of all 17 IR-active fundamental modes were observed in all specimens except pyrope. Of the 17 modes, 16 show linear correlations between frequency and composition along the pyrope-almandine join. The remaining mode, assigned to translations of the divalent cations against the O framework, exhibits two-mode behavior. The trends show that two modes in pyrope are accidentally degenerate. Frequencies of garnets with up to 10 mol% spessartine and grossular contents lie on the trends defined by the pyrope-almandine samples with negligible impurities. However, one to three additional modes are seen for some intermediate compositions, apparently resulting from either resonances among combination modes or two-mode behavior due to high Ca contents. The nearly linear behavior of the modes indicates that mixing should be close to ideal for the pyrope-almandine series because the lattice contribution dominates heat capacity, entropy, and compressibility. 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.