HR: 0830h
AN: V51I-0390    [PDF]
TI: Vapor Separation and Migration in a Solidifying and Compacting Crystal Pile
AU: * Boudreau, A E
EM: boudreau@duke.edu
AF: Duke University, Div. Earth & Ocean Sciences Box 90227, Durham, NC 27708 United States
AB: The effect of vapor separation and migration in a crystal pile undergoing simultaneous crystallization and compaction has been investigated using a modified version of the IRIDIUM program. This program incorporates a simplified version of the MELTS program of Ghiorso and others coupled with compaction-driven thermal and mass transfer based on the works of Mckenzie and Shirley. The program also allows for trace-element modeling. The program has been modified to allow the independent upward migration of a separate vapor phase. It also now incorporates a COHS gas phase and sulfide phases. The solidification of a crystal + liquid assemblage that is loosing heat out the bottom results in the eventual separation of a volatile-rich fluid or vapor. The vapor separated from cooler parts of the crystal pile migrates upward to hotter assemblages and redissolves in the interstitial liquid that has not reached vapor saturation. This influx of volatiles results in a remelting of the solids, producing a liquid-rich zone within the crystal pile. This liquid-rich zone migrates upward with time, and mimics a zone-refining metallurgical process. If the remelting zone approaches the top of the crystal pile, the effect is a relatively sharp transition from liquid-rich to liquid-poor assemblages. After the zone has passed any given horizon, major mineral compositions are relatively unaffected (e.g., there is no readily apparent change in mg\# or mineral porportions). However, vapor-soluble elements are moved upward over time. In the case of sulfur, this can result in the upward migration of a sulfide-saturation zone with time. The remelting of pre-existing solids may lead to zones of instability within the crystal pile. Examples of slumping, shearing and layer disruption from the Stillwater Complex are shown that may have been caused by such a process.
DE: 3640 Igneous petrology
DE: 3665 Mineral occurrences and deposits
DE: 5114 Permeability and porosity
DE: 8424 Hydrothermal systems (8135)
DE: 8434 Magma migration
SC: Volcanology, Geochemistry, Petrology [V]
MN: 2003 Fall Meeting