Fe-oxide microcrystals in welded tuff from southern Nevada: Origin of remanence carriers by precipitation in volcanic glass

Abstract

Research Article| June 01, 1988 Fe-oxide microcrystals in welded tuff from southern Nevada: Origin of remanence carriers by precipitation in volcanic glass Charles M. Schlinger; Charles M. Schlinger 1Department of Geology and Geophysics, University of Utah, Salt Lake City, Utah 84112 Search for other works by this author on: GSW Google Scholar J. G. Rosenbaum; J. G. Rosenbaum 2U.S. Geological Survey, M.S. 964, Denver, Colorado 80225 Search for other works by this author on: GSW Google Scholar David R. Veblen David R. Veblen 3Department of Earth and Planetary Sciences, Johns Hopkins University, Baltimore, Maryland 21218 Search for other works by this author on: GSW Google Scholar Author and Article Information Charles M. Schlinger 1Department of Geology and Geophysics, University of Utah, Salt Lake City, Utah 84112 J. G. Rosenbaum 2U.S. Geological Survey, M.S. 964, Denver, Colorado 80225 David R. Veblen 3Department of Earth and Planetary Sciences, Johns Hopkins University, Baltimore, Maryland 21218 Publisher: Geological Society of America First Online: 02 Jun 2017 Online ISSN: 1943-2682 Print ISSN: 0091-7613 Geological Society of America Geology (1988) 16 (6): 556–559. https://doi.org/10.1130/0091-7613(1988)016<0556:FOMIWT>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 Charles M. Schlinger, J. G. Rosenbaum, David R. Veblen; Fe-oxide microcrystals in welded tuff from southern Nevada: Origin of remanence carriers by precipitation in volcanic glass. Geology 1988;; 16 (6): 556–559. doi: https://doi.org/10.1130/0091-7613(1988)016<0556:FOMIWT>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 Although it is widely recognised that remanent magnetism in ash-flow tuffs is carried by fine-grained Fe oxides, the origin, mineralogy, and significance of such magnetic carriers are not well understood. We have obtained transmission electron microscope images of distinctive Fe-oxide microcrystals in rhyolitic samples located 3.8, 7.6, and 18.5 m above the base of a 110-m-thick section of the Miocene Tiva Canyon Member of the Paintbrush Tuff. The Fe-oxide microcrystals are lath shaped and increase in size from ∼20 x 140 nm in the lowermost sample (near base of the member) to ∼120 x 800 nm in the uppermost sample (within the flow interior). Microcrystals in this size range are within or close to the range of single-domain grain size for magnetite. Electron diffraction and analytical X-ray data indicate that the microcrystals in the lower two samples are cubic Fe-oxides (magnetite/maghemite), with less than 10 mol% Ti end member, and that those in the uppermost sample are manganiferous hematite. Systematic variations in magnetic properties are consistent with the observed variations in size and mineralogy of the microcrystals. These micro-crystals are morphologically distinct from grains that we interpret to be fragments of phenocrysts. The morphology and spatial distribution of the microcrystals as well as their increase in grain size, from the rapidly cooled base of the ash-flow sheet into the flow interior, are consistent with an origin by nucleation and growth from volcanic glass at elevated temperature, subsequent to emplacement. 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.