Melt-inclusion–hosted excess 40Ar in quartz crystals of the Bishop and Bandelier magma systems

Abstract

Research Article| March 01, 2001 Melt-inclusion–hosted excess 40Ar in quartz crystals of the Bishop and Bandelier magma systems J.A. Winick; J.A. Winick 1Department of Earth and Environmental Science, New Mexico Institute of Mining and Technology, Socorro, New Mexico 87801, USA Search for other works by this author on: GSW Google Scholar W.C. McIntosh; W.C. McIntosh 2New Mexico Bureau of Mines and Mineral Resources, Socorro, New Mexico 87801, USA Search for other works by this author on: GSW Google Scholar N.W. Dunbar N.W. Dunbar 2New Mexico Bureau of Mines and Mineral Resources, Socorro, New Mexico 87801, USA Search for other works by this author on: GSW Google Scholar Author and Article Information J.A. Winick 1Department of Earth and Environmental Science, New Mexico Institute of Mining and Technology, Socorro, New Mexico 87801, USA W.C. McIntosh 2New Mexico Bureau of Mines and Mineral Resources, Socorro, New Mexico 87801, USA N.W. Dunbar 2New Mexico Bureau of Mines and Mineral Resources, Socorro, New Mexico 87801, USA Publisher: Geological Society of America Received: 14 Jun 2000 Revision Received: 09 Nov 2000 Accepted: 29 Nov 2000 First Online: 02 Jun 2017 Online ISSN: 1943-2682 Print ISSN: 0091-7613 Geological Society of America Geology (2001) 29 (3): 275–278. https://doi.org/10.1130/0091-7613(2001)029<0275:MIHEAI>2.0.CO;2 Article history Received: 14 Jun 2000 Revision Received: 09 Nov 2000 Accepted: 29 Nov 2000 First Online: 02 Jun 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn Email Permissions Search Site Citation J.A. Winick, W.C. McIntosh, N.W. Dunbar; Melt-inclusion–hosted excess 40Ar in quartz crystals of the Bishop and Bandelier magma systems. Geology 2001;; 29 (3): 275–278. doi: https://doi.org/10.1130/0091-7613(2001)029<0275:MIHEAI>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 40Ar/39Ar experiments on melt-inclusion–bearing quartz (MIBQ) from the Bishop and Bandelier Tuff Plinian deposits indicate high concentrations of excess 40Ar in melt inclusions. Two rhyolite glass melt inclusion populations are present in quartz; exposed melt inclusions and trapped melt inclusions. Air-abrasion mill grinding and hydrofluoric acid treatments progressively remove exposed melt inclusions while leaving trapped melt inclusions unaffected. Laser step-heating of MIBQ yields increasing apparent ages as a function of exposed melt inclusion removal, reflecting the higher nonatmospheric 40Ar concentrations hosted in trapped melt inclusions. Exposed melt inclusion–free MIBQ from the Bishop, Upper Bandelier, and Lower Bandelier Tuffs yield total-gas ages of 3.70 ± 1.00 Ma, 11.54 ± 0.87 Ma, and 14.60 ± 1.50 Ma, respectively. We interpret these old apparent ages as compelling evidence for the presence of excess 40Ar in MIBQ. Trapped melt inclusions in sanidine phenocrysts may contain excess 40Ar concentrations similar to those in MIBQ. This excess 40Ar has the potential to increase single-crystal laser-fusion ages of sanidine by tens of thousands of years, relative to the actual eruption age. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.