Geologic origin of magnetic volcanic glasses in the KBS tuff

Abstract

Research Article| November 01, 1986 Geologic origin of magnetic volcanic glasses in the KBS tuff 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 Rebecca M. Smith; Rebecca M. Smith 1Department of Geology and Geophysics, University of Utah, Salt Lake City, Utah 84112 Search for other works by this author on: GSW Google Scholar David R. Veblen David R. Veblen 2Department 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 Rebecca M. Smith 1Department of Geology and Geophysics, University of Utah, Salt Lake City, Utah 84112 David R. Veblen 2Department of Earth and Planetary Sciences, Johns Hopkins University, Baltimore, Maryland 21218 Publisher: Geological Society of America First Online: 01 Jun 2017 Online ISSN: 1943-2682 Print ISSN: 0091-7613 Geological Society of America Geology (1986) 14 (11): 959–962. https://doi.org/10.1130/0091-7613(1986)14<959:GOOMVG>2.0.CO;2 Article history First Online: 01 Jun 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn Email Permissions Search Site Citation Charles M. Schlinger, Rebecca M. Smith, David R. Veblen; Geologic origin of magnetic volcanic glasses in the KBS tuff. Geology 1986;; 14 (11): 959–962. doi: https://doi.org/10.1130/0091-7613(1986)14<959:GOOMVG>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 SocietyGeology Search Advanced Search Abstract Volcanic glass shards and banded pumice from the KBS tuff of northern Kenya exhibit marked variations in magnetic susceptibility and color (colorless to dark brown). The darker glass shards exhibit superparamagnetism, which we now know to be carried by a population of tiny microcrystals of Fe-rich cubic oxide, ∼20 to ∼100 A in size, thought to be magnetite. A theory for their origin is one of nucleation and growth (precipitation) in quenched homogeneous glass (colorless) at temperatures of ∼700–1000 °C during and immediately subsequent to eruption. Results from high-temperature heating experiments on KBS shards support this idea. The precipitate appears in the KBS shards as a consequence of their cooling history and is the origin of their coloring; the origin cannot lie in negligible compositional differences between the colorless and darkest shards. On the other hand, banded pumice from the KBS tuff has both dark and colorless glasses of differing compositions. The pumice appears banded because precipitation occurred preferentially in the Fe-rich glass. Although magma mixing may have played a role in the eruption of these materials, on the basis of our survey of distal eruptive products, it would appear that the volumetric amount of the mafic end member (dark pumice) was insubstantial. 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.