High-pressure metamorphism during the Llano orogeny inferred from Proterozoic eclogite remnants

Abstract

Research Article| May 01, 1988 High-pressure metamorphism during the Llano orogeny inferred from Proterozoic eclogite remnants Amy Wilkerson; Amy Wilkerson 1Department of Geological Sciences, University of Texas, Austin, Texas 78713 Search for other works by this author on: GSW Google Scholar William D. Carlson; William D. Carlson 1Department of Geological Sciences, University of Texas, Austin, Texas 78713 Search for other works by this author on: GSW Google Scholar Douglas Smith Douglas Smith 1Department of Geological Sciences, University of Texas, Austin, Texas 78713 Search for other works by this author on: GSW Google Scholar Geology (1988) 16 (5): 391–394. https://doi.org/10.1130/0091-7613(1988)016<0391:HPMDTL>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 MailTo Tools Icon Tools Get Permissions Search Site Citation Amy Wilkerson, William D. Carlson, Douglas Smith; High-pressure metamorphism during the Llano orogeny inferred from Proterozoic eclogite remnants. Geology 1988;; 16 (5): 391–394. doi: https://doi.org/10.1130/0091-7613(1988)016<0391:HPMDTL>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 Mineral chemistries and textures in mafic garnet-pyroxene rock within the Lost Creek Gneiss in the Purdy Hill quadrangle, Mason County, Texas, record three distinct P-T events, two of them at pressures higher than any previously documented for these Grenville-age rocks. The earliest metamorphic episode produced an eclogitic assemblage of pyrope-rich almandine + sodian augite + orthopyroxene + pargasitic amphibole. Some orthopyroxene cores record pressures greater than 15 kbar even for the most conservative estimated temperature of 500 °C. Garnet and orthopyroxene rims and matrix clinopyroxene and amphibole record a second event at ∼750 °C and 8 kbar. Symplectites of clinopyroxene + plagioclase and coronas around garnet of plagioclase + amphibole + magnetite formed in response to reheating and hydration associated with postkinematic intrusion at the amphibolite facies conditions (600-650 °C, 3.5-5 kbar) commonly recorded in the region. Recognition of early high-pressure metamorphic episodes markedly strengthens the correlation between these rocks and other Grenville-age exposures along the continental margin and provides petrologic support for models invoking Proterozoic subduction accompanying the Llano orogeny. 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.