Title: A magmatic geohygrometer: Application to Mount St. Helens and other dacitic magmas
Abstract: Research Article| October 01, 1984 A magmatic geohygrometer: Application to Mount St. Helens and other dacitic magmas Celia Merzbacher; Celia Merzbacher 1Geosciences Department, Pennsylvania State University, University Park, Pennsylvania 16802 Search for other works by this author on: GSW Google Scholar David H. Eggler David H. Eggler 1Geosciences Department, Pennsylvania State University, University Park, Pennsylvania 16802 Search for other works by this author on: GSW Google Scholar Geology (1984) 12 (10): 587–590. https://doi.org/10.1130/0091-7613(1984)12<587:AMGATM>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 MailTo Tools Icon Tools Get Permissions Search Site Citation Celia Merzbacher, David H. Eggler; A magmatic geohygrometer: Application to Mount St. Helens and other dacitic magmas. Geology 1984;; 12 (10): 587–590. doi: https://doi.org/10.1130/0091-7613(1984)12<587:AMGATM>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 Compositions of andesitic to dacitic melts in equilibrium with plagioclase, orthopyroxene, and clinopyroxene have been experimentally calibrated as a geohygrometer. Application to Melson's data on melt inclusions and matrix glasses from the 1980–1982 cycle of eruptions of Mount St. Helens reveals systematic dewatering trends—ca. 4% (1980) to 1% (1982) H2O in subliquidus (intratelluric) melt in pyroclastics and 2%–3% (1980) to 1% (1982) in subliquidus melt in dome-building dacites. Before each pyroclastic event, intratelluric crystallization achieved melt H2O contents of ca. 6% (at a depth of at least 8 km), a necessary condition for crystallization of amphibole. Dewatering trends indicate that individual magma blobs or ribbons then ascended to successively higher levels over the 3-yr cycle, from a minimum depth of 4 km in 1980 to 0.35 km in 1982, and pyroclastically erupted.Comparison of Mount St. Helens compositions to worldwide andesites and dacites suggests that near-liquidus arc magmas that crystallize plagioclase and pyroxenes contain 1%–2% H2O, on average, whereas magmas in continental margins contain appreciably more H2O. 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.
Publication Year: 1984
Publication Date: 1984-01-01
Language: en
Type: article
Indexed In: ['crossref']
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Cited By Count: 152
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