Forgotten major elements: Hydrogen and oxygen variation in biotite from metapelites

Abstract

Research Article| October 01, 1991 Forgotten major elements: Hydrogen and oxygen variation in biotite from metapelites M. Darby Dyar; M. Darby Dyar 1Department of Geological Sciences, University of Oregon, Eugene, Oregon 97403 Search for other works by this author on: GSW Google Scholar Michael T. Colucci; Michael T. Colucci 2Stable Isotope Laboratory, Institute for the Study of Earth and Man, Southern Methodist University, Dallas, Texas 75275 Search for other works by this author on: GSW Google Scholar Charles V. Guidotti Charles V. Guidotti 3Department of Geological Sciences, University of Maine, Orono, Maine 04469 Search for other works by this author on: GSW Google Scholar Author and Article Information M. Darby Dyar 1Department of Geological Sciences, University of Oregon, Eugene, Oregon 97403 Michael T. Colucci 2Stable Isotope Laboratory, Institute for the Study of Earth and Man, Southern Methodist University, Dallas, Texas 75275 Charles V. Guidotti 3Department of Geological Sciences, University of Maine, Orono, Maine 04469 Publisher: Geological Society of America First Online: 02 Jun 2017 Online ISSN: 1943-2682 Print ISSN: 0091-7613 Geological Society of America Geology (1991) 19 (10): 1029–1032. https://doi.org/10.1130/0091-7613(1991)019<1029:FMEHAO>2.3.CO;2 Article history First Online: 02 Jun 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn Email Permissions Search Site Citation M. Darby Dyar, Michael T. Colucci, Charles V. Guidotti; Forgotten major elements: Hydrogen and oxygen variation in biotite from metapelites. Geology 1991;; 19 (10): 1029–1032. doi: https://doi.org/10.1130/0091-7613(1991)019<1029:FMEHAO>2.3.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 SocietyGeology Search Advanced Search Abstract Variations in the H+ and O2- content of minerals have been virtually ignored since the advent of the electron microprobe in the mid-1960s. Such studies do not serve as a basis for consideration of the variation of other major constituents such as Fe3+, H+, and O2-. We report results of a comprehensive study of all major element compositional variation in biotite using samples from a suite of metapelites ranging from lower garnet to sillimanite + K-feldspar grades. The data show that Fe3+ remains constant within analytical error while percentages by weight of H2O and O decrease and increase, respectively, with increasing metamorphic grade. H+ and O2- contents of biotite appear to be highly sensitive to temperature and pressure. Samples from low metamorphic grades contain bulk H+ contents >4H+/formula unit. Excess H+ probably occupies "vacancies" in the interlayer sites as either H2O or H3O. These results will have an impact on geoscience disciplines that make assumptions about stoichiometry of hydrous phases. For example, the temperature range of reactions involving the breakdown of hydrous phases with more or less H+ than predicted will change, in some cases dramatically, and any calculations involving water activities must be modified to consider H+ variation. Partitioning of H+ among coexisting hydrous phases (δD studies) may be affected by both amount of H+ and its location and bonding (interlayer H2O or H3O vs. OH-). Ar diffusivities calculated for 40Ar/39Ar work will be influenced by the H+ occupancy in the interlayer sites. Cation substitution models for H+-bearing phases need to consider exchanges involving both H+ and O2-. 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.