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Dynamics of magma withdrawal from stratified magma chambers

1986; Geological Society of America; Volume: 14; Issue: 9 Linguagem: Inglês

10.1130/0091-7613(1986)14 2.0.co;2

1943-2682

Frank J. Spera, David A. Yuen, John C. Greer, Granville Sewell,

CO2 Sequestration and Geologic Interactions

Research Article| September 01, 1986 Dynamics of magma withdrawal from stratified magma chambers Frank J. Spera; Frank J. Spera 1Department of Geological Sciences, University of California, Santa Barbara, California 93106 Search for other works by this author on: GSW Google Scholar David A. Yuen; David A. Yuen 2Department of Geology and Geophysics and Minnesota Supercomputer Institute University of Minnesota, Minneapolis, Minnesota 55455 Search for other works by this author on: GSW Google Scholar John C. Greer; John C. Greer 3Department of Geology, Arizona State University, Tempe, Arizona 85287 Search for other works by this author on: GSW Google Scholar Granville Sewell Granville Sewell 4Department of Mathematical Sciences, University of Texas, El Paso, Texas 79968 Search for other works by this author on: GSW Google Scholar Geology (1986) 14 (9): 723–726. https://doi.org/10.1130/0091-7613(1986)14 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 Frank J. Spera, David A. Yuen, John C. Greer, Granville Sewell; Dynamics of magma withdrawal from stratified magma chambers. Geology 1986;; 14 (9): 723–726. doi: https://doi.org/10.1130/0091-7613(1986)14 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 The time history of magma withdrawal through a central vent from a flat-roofed chamber strongly stratified in density and viscosity has been numerically modeled. Important parameters include the geometry of the reservoir; the initial vertical compositional profile; the ratio of viscous, inertial, and gravitational forces; and the basal normal stress driving the eruption. Finite critical stresses in the range 102 to 106 Pa are required to initiate and maintain an eruption. The composition-time history of erupted magma depends strongly on the reservoir/conduit width (A) such that large A increases (1) the time interval during which mixed magma is erupted, (2) the steady-state time (ts), defined as the time at which the composition of erupted magma is within 1% of the initial basal composition, and (3) the fraction of silicic magma trapped within the chamber. Steady-state times increase by a factor of two as the viscosity contrast increases from 1 to 102, and they become independent of viscosity variations for contrasts > 104. It is possible to distinguish continuous from discontinuous (i.e., layered) pre-eruptive gradients within chambers by comparing synthesized and measured geochemical stratigraphic sections for particular pyroclastic flow deposits. A mechanism for the generation of compositional gaps in ignimbrites following either a short eruption hiatus or an abrupt increase or decrease of the discharge during an otherwise quasi-steady eruption is quantitatively predicted. Most important, a compositional gap or a series of gaps within a pyroclastic deposit does not necessarily mean that one existed within the chamber before the eruption. It is impossible to invert stratigraphically controlled geochemical data to obtain in situ chamber compositional structure if one does not have detailed information regarding the location of vents and the variation of magma discharge with time during a pyroclastic eruption. 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.