HR: 0800h
AN: V21A-0394    [Abstracts]
TI: Expected Behavior of Basaltic Magma with the Proposed High Level Nuclear Repository at Yucca Mountain, Nevada
AU: Apted, M
EM: mapted@monitorsci.com
AF: Monitor Scientific LLC, 3900 S. Wadsworth Blvd #555, Denver, CO 80235,
AU: * Morrissey, M
EM: mmorriss@mines.edu
AF: Colorado School of Mines, GGE, Golden, CO 80403,
AB: The expected series of eruptive events for a future igneous event in Yucca Mountain within the next 1 MY is comparable to that at Lathrop Wells basalt center and other Crater Flats Quaternary volcanoes. Lathrop Wells and Crater Flats Quaternary volcanoes are, in general, comprised of a single scoria cone with one or two lava flow fields extending from the base. The lava flow fields associated with scoria cones all appear to extend from the base of a scoria cone and to be comprised of lava terraces. A three-dimensional model of the plumbing system for a possible future igneous event is presented in this paper, based on the characteristic features of eruptive deposits at Lathrop Wells and other Crater Flats Quaternary volcanoes. Also described in the model are consequences related to the interaction between magma and the repository. The repository is expected to be 200-300 m below the surface and comprised of parallel drifts 5 m in diameter, 0.5-1.0 km in length and spaced 85 m. Each drift is to be filled with a series of 1.8 m diameter waste packages made of Alloy 22 stainless steel. The conceptual model of the plumbing system and related consequences are described in six stages. Stage 1 Intersection of dike with drift: One dike will intersect the repository. The width of a future dike in YMR is expected to vary along the length with a maximum value of < 4.0 m at repository depths. The number of drifts that will be intersected by the dike will be 6-24 depending on the lateral extent of the dike through the repository. Stage 2 Initial stage magma-drift interaction: The lateral variation in magma properties will produce, in general, two different styles of expected activity upon entering a drift: a mixture of gas and fragments of magma characteristic of a lava fountain at wide portions of the dike, and crystallizing magma relatively depleted in volatiles at the narrowest part of the dike. A spray of pyroclastics is expected inside a drift from a lava fountain that will bombard and coat waste packages with magma. Crystallizing magma relatively depleted in volatiles will be a slow moving crystallizing flow and is expected to behave like a plug sealing the drift. Stage 3 Surface activity: initial cone building stage: Magma that is not diverted into the drift will follow the crack tip and make its way to the surface and erupt at the surface along the fissure as a curtain of lava fountains. A conduit or cone building part of the eruption will develop at the widest part of the dike. Stage 4 Second stage of magma drift interaction: Strombolian activity at the repository depth is expected to occur in only one drift; the drift that is intersected by the widest part the dike. This drift will be inundated with pyroclastic material associated with the early cone building Strombolian events. Lava is expected to enter an adjacent drift as discrete pulses. Stage 5 Surface activity: final cone building phase: At the surface, activity will transition to a more violent Strombolian style. Additional discrete pulses of lava may occur. Stage 6 Final stage magma drift interaction: Magma entering drifts at this stage will be either a pyroclastic flow or lava.
DE: 8414 Eruption mechanisms and flow emplacement
DE: 8425 Effusive volcanism
DE: 8488 Volcanic hazards and risks
SC: Volcanology, Geochemistry, Petrology [V]
MN: 2007 Fall Meeting