Upper mantle origin of plagioclase megacrysts from plagioclase-ultraphyric mid-oceanic ridge basalt

Research Article| November 30, 2018 Upper mantle origin of plagioclase megacrysts from plagioclase-ultraphyric mid-oceanic ridge basalt Mélissa J. Drignon; Mélissa J. Drignon 1College of Earth, Ocean and Atmospheric Science, Oregon State University, Corvallis, Oregon 97331, USA Search for other works by this author on: GSW Google Scholar Roger L. Nielsen; Roger L. Nielsen 1College of Earth, Ocean and Atmospheric Science, Oregon State University, Corvallis, Oregon 97331, USA Search for other works by this author on: GSW Google Scholar Frank J. Tepley, III; Frank J. Tepley, III 1College of Earth, Ocean and Atmospheric Science, Oregon State University, Corvallis, Oregon 97331, USA Search for other works by this author on: GSW Google Scholar Robert J. Bodnar Robert J. Bodnar 2Department of Geosciences, Virginia Tech, Blacksburg, Virginia 24061, USA Search for other works by this author on: GSW Google Scholar Author and Article Information Mélissa J. Drignon 1College of Earth, Ocean and Atmospheric Science, Oregon State University, Corvallis, Oregon 97331, USA Roger L. Nielsen 1College of Earth, Ocean and Atmospheric Science, Oregon State University, Corvallis, Oregon 97331, USA Frank J. Tepley, III 1College of Earth, Ocean and Atmospheric Science, Oregon State University, Corvallis, Oregon 97331, USA Robert J. Bodnar 2Department of Geosciences, Virginia Tech, Blacksburg, Virginia 24061, USA Publisher: Geological Society of America Received: 30 Aug 2018 Revision Received: 01 Nov 2018 Accepted: 06 Nov 2018 First Online: 30 Nov 2018 Online Issn: 1943-2682 Print Issn: 0091-7613 © 2018 Geological Society of America Geology (2019) 47 (1): 43–46. https://doi.org/10.1130/G45542.1 Article history Received: 30 Aug 2018 Revision Received: 01 Nov 2018 Accepted: 06 Nov 2018 First Online: 30 Nov 2018 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation Mélissa J. Drignon, Roger L. Nielsen, Frank J. Tepley, Robert J. Bodnar; Upper mantle origin of plagioclase megacrysts from plagioclase-ultraphyric mid-oceanic ridge basalt. Geology 2018;; 47 (1): 43–46. doi: https://doi.org/10.1130/G45542.1 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 Rigorous petrogenetic interpretation of data from melt inclusions (MI) and their host phenocrysts commonly requires knowledge of the crystallization pressure. Pressures of trapping of MI are commonly estimated based on the H2O and CO2 concentrations of the inclusions, but their original concentrations may be modified as a result of various post-entrapment processes. Most studies of mafic magmas employ olivine- or pyroxene-hosted MI, largely based on the assumption that plagioclase phenocrysts do not retain volatiles and/or are the product of late-stage crystallization. We have investigated the effects of post-entrapment processes on plagioclase-hosted MI in one plagioclase-ultraphyric basalt from the Blanco transform fault (offshore Oregon, USA). Our results demonstrate that plagioclase-hosted MI do not lose CO2 even after being heated to the entrapment temperature for 4 d. The reconstructed CO2 (glass + vapor) concentration in the MI indicates that the plagioclase megacrysts crystallized at depths equal to or below the local Moho, at minimum pressures of 230–910 MPa. Our results confirm that the plagioclase crystallized in the mantle, and that reliable trapping pressures can be obtained from MI in plagioclase following rehomogenization experiments. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.