Trace element zoning and incipient metamictization in a lunar zircon; application of three microprobe techniques

Abstract

Other| August 01, 1996 Trace element zoning and incipient metamictization in a lunar zircon; application of three microprobe techniques Brigitte Wopenka; Brigitte Wopenka Washington University, Department of Earth and Planetary Sciences, St. Louis, MO, United States Search for other works by this author on: GSW Google Scholar Bradley L. Jolliff; Bradley L. Jolliff Search for other works by this author on: GSW Google Scholar Ernst Zinner; Ernst Zinner Search for other works by this author on: GSW Google Scholar Daniel T. Kremser Daniel T. Kremser Search for other works by this author on: GSW Google Scholar American Mineralogist (1996) 81 (7-8): 902–912. https://doi.org/10.2138/am-1996-7-813 Article history first online: 02 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Twitter LinkedIn Tools Icon Tools Get Permissions Search Site Citation Brigitte Wopenka, Bradley L. Jolliff, Ernst Zinner, Daniel T. Kremser; Trace element zoning and incipient metamictization in a lunar zircon; application of three microprobe techniques. American Mineralogist 1996;; 81 (7-8): 902–912. doi: https://doi.org/10.2138/am-1996-7-813 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 SocietyAmerican Mineralogist Search Advanced Search Abstract We have determined major (Si, Zr, Hf), minor (Al, Y, Fe, P), and trace element (Ca, Sc, Ti, Ba, REE, Th, U) concentrations and Raman spectra of a zoned, 200 μm zircon grain in lunar sample 14161,7069, a quartz monzodiorite breccia collected at the Apollo 14 site. Analyses were obtained on a thin section in situ with an ion microprobe, an electron microprobe, and a laser Raman microprobe. The zircon grain is optically zoned in birefringence, a reflction of variable (incomplete) metamictization resulting from zonation in U and Th concentrations. Variations in the concentrations of U and Th correlate strongly with those ofother high-field-strength trace elements and with changes in Raman spectral parameters. Concentrations ofU and Th range from 21 to 55 ppm and 6 to 31 ppm, respectively, and correlate with lower Raman peak intensities, wider Raman peaks, and shifted Si-O peak positions. Concentrations of heavy rare earth elements range over a factor of three to four and correlate with intensities offluorescence peaks. Correlated variations in trace element concentrations reflect the original magmatic differentiation of the parental melt∼4 b.y. ago. Degradation of the zircon structure, as reflected by the observed Raman spectral parameters,has occurred in this sample over arange of a-decay event dose from ∼5.2 × 1014 to 1.4 × 1015 decay eventsper milligram of zircon, as calculated from the U and Th concentrations. This dose is well below the ∼1016 events per milligram cumulative dose that causes complete metamictization and indicates that laser Raman microprobe spectroscopy is an analytical technique that is very sensitive to the radiation-induced damage in zircon. 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.