HR: 09:45h
AN: V41F-08 INVITED    [Abstracts]
TI: Dynamical Constraints on the Life Cycle of Voluminous Silicic Systems: How to Build, Maintain, and Destroy Shallow Silicic Magma Bodies
AU: * Dufek, J
EM: dufek@berkeley.edu
AF: University of California, Berkeley, 307 McCone Hall, Berkeley, CA 94720, United States
AU: Karlstrom, L
EM: leif@berkeley.edu
AF: University of California, Berkeley, 307 McCone Hall, Berkeley, CA 94720, United States
AU: Bachmann, O
EM: bachmano@u.washington.edu
AF: University of Washington, Box 351310, Seattle, WA 98195, United States
AU: Bergantz, G W
EM: bergantz@u.washington.edu
AF: University of Washington, Box 351310, Seattle, WA 98195, United States
AU: Leeman, W
EM: leeman@rice.edu
AF: National Science Foundation, 4201 Wilson Blvd., Arlington, VA 22230, United States
AU: Annen, C
EM: Catherine.Annen@terre.unige.ch
AF: Université de Genà¨ve, 13 rue des Maraà®chers, Geneva, 1205, Switzerland
AB: The generation, accumulation and eruption of silicic magmas in the shallow crust occurs on a wide range of length and timescales. Here we focus on two questions related to these interrelated processes: 1.) What are the energy and dynamic constraints for the relative proportions of crustal and mantle melts in the production of silicic systems? 2.) What processes can alleviate the so called "room problem", and how does this contribute to the longevity of the system? We address the first two questions through a coupled finite volume and finite element approach to determine the evolving thermal and stress fields in response to magma injection in the upper crust. We perform a suite of two- dimensional simulations over a range of magmatic fluxes and different regional stresses. To constrain the volume and depth of assimilation of crustal materials we also perform oxygen isotope calculations that are coupled with the evolving thermal and permeability structure of the crust. The rate of δ¹⁸O-depletion of the crust is controlled by both the supply of low δ¹⁸O meteoric waters at depth and by the temperature dependent kinetics of oxygen exchange between the water and the permeable crystal framework. We find that extensive crustal melting and significant δ¹⁸O-depletion, such as is found in many Snake River rhyolites, can be explained by a self-consistent combination of elevated basaltic flux, enhanced upper crustal permeability, and magmatic volume accommodation, such as by extension. This stands in contrast to low flux silicic systems such as the Kos Plateau Tuff in the Aegean arc that are isotopically very mantle-like.
DE: 8404 Volcanoclastic deposits
DE: 8410 Geochemical modeling (1009, 3610)
DE: 8413 Subduction zone processes (1031, 3060, 3613, 8170)
DE: 8439 Physics and chemistry of magma bodies
DE: 8440 Calderas
SC: Volcanology, Geochemistry, Petrology [V]
MN: 2007 Fall Meeting