HR: 12:05h
AN: T32A-08    [Abstracts]
TI: Geodyamic Models of the Tectonomagmatic Evolution of the West Antarctic Rift System
AU: * Anoka, J L
EM: jlanoka@lamar.colostate.edu
AF: Colorado State University, 1482 Geosciences, Fort Collins, CO 80523, United States
AU: Harry, D L
EM: dharry@cnr.colostate.edu
AF: Colorado State University, 1482 Geosciences, Fort Collins, CO 80523, United States
AB: Finite element geodynamic models reproduce the general aspects of the style and timing of extension in the West Antarctic Rift System (WARS). In particular, the models simulate a prolonged period of diffuse extension throughout the WARS during the Cretaceous and early Cenozoic followed by later focused extension in the Victoria Land Basin during the middle Paleogene. Two families of models are identified that are consistent with the Paleogene onset of magmatism in the West Antarctic Rift System under both normal and warm (70-120º hotter than global average) mantle potential temperatures. The two families of models produce distinctly different melt distribution patterns across the WARS. In models invoking normal mantle temperatures the greatest thickness of melt is confined to the Victoria Land Basin region. In models invoking warmer mantle temperatures, the greatest thickness of melt is widely distributed in the region currently underlaying the West Antarctic Ice Sheet. The models indicate that 1) the onset of Cenozoic magmatism in the Victoria Land Basin can be explained as rift induced without requiring the impingement of a plume or a change in plate motion, 2) if rifting is associated with a plume then the magmatic rocks under the West Antarctic Ice Sheet should be late Cretaceous to early Cenozoic in age, and 3) if the magmatic rocks under the West Antarctic Ice Sheet are older or younger than the main stage of rifting (ca. 105 Ma to 35 Ma), a syn-extensional plume could not have been present.
DE: 8105 Continental margins: divergent (1212, 8124)
DE: 8109 Continental tectonics: extensional (0905)
DE: 8159 Rheology: crust and lithosphere (8031)
DE: 8178 Tectonics and magmatism
SC: Tectonophysics [T]
MN: 2007 Fall Meeting