Olivine Crystal Types in Harrisitic Rocks of the Rhum Pluton and in Archean Spinifex Rocks

Research Article| November 01, 1974 Olivine Crystal Types in Harrisitic Rocks of the Rhum Pluton and in Archean Spinifex Rocks COLIN H. DONALDSON COLIN H. DONALDSON 1Lunar Science Institute, 3303 Nasa Road 1, Houston, Texas 77058 and Department of Geology, University of St. Andrews, St. Andrews, Fife, Scotland Search for other works by this author on: GSW Google Scholar Author and Article Information COLIN H. DONALDSON 1Lunar Science Institute, 3303 Nasa Road 1, Houston, Texas 77058 and Department of Geology, University of St. Andrews, St. Andrews, Fife, Scotland Publisher: Geological Society of America First Online: 01 Jun 2017 Online ISSN: 1943-2674 Print ISSN: 0016-7606 Geological Society of America GSA Bulletin (1974) 85 (11): 1721–1726. https://doi.org/10.1130/0016-7606(1974)85<1721:OCTIHR>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 COLIN H. DONALDSON; Olivine Crystal Types in Harrisitic Rocks of the Rhum Pluton and in Archean Spinifex Rocks. GSA Bulletin 1974;; 85 (11): 1721–1726. doi: https://doi.org/10.1130/0016-7606(1974)85<1721:OCTIHR>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 SocietyGSA Bulletin Search Advanced Search Abstract Skeletal and dendritic olivine crystals in the Archean volcanic ultramafic spinifex rocks and in harrisitic ultramafic layers of the Rhum pluton are classified as (1) plate, (2) randomly oriented, (3) porphyritic, or (4) branching type. Volcanic and plutonic examples are remarkably similar. Each type records the degree of pre-nucleation supersaturation with olivine that was attained by the parent melt. The rapid induction of supersaturation necessary to form skeletons and dendrites in a plutonic environment is attributed to changing water content or adiabatic expansion of the magma. The olivine crystals in harrisitic and spinifex rocks are not quench crystals; they grew rapidly from olivine-rich melts as the result of extreme supersaturation induced by slow cooling and slight supercooling below a liquidus with shallow slope in temperature-composition space. Skeletal and dendritic olivine crystals grow readily in magma and are poor indices of cooling rate and crystallization environment. 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.