HR: 11:20h
AN: SF32A-04 INVITED     [Abstracts]
TI: The Curious Decoupling of Magmatism and Plate Tectonics During the Cenozoic in Western North America: Insight From the NAVDAT Database
AU: * Glazner, A F
EM: afg@unc.edu
AF: Univ. of North Carolina, Dept. of Geological Sciences, CB# 3315, Chapel Hill, NC 27599 United States
AU: Walker, J D
EM: jdwalker@ku.edu
AF: Univ. of Kansas, Dept. of Geology, Lawrence, KS 66045 United States
AU: Farmer, G L
EM: farmer@cires.colorado.edu
AF: Univ. of Colorado, Dept. of Geological Sciences, Boulder, CO 80309 United States
AU: Bowers, T D
EM: tbowers@ku.edu
AF: Univ. of Kansas, Dept. of Geology, Lawrence, KS 66045 United States
AB: Since the widespread acceptance of plate tectonics, magmatism in the western U.S. has been explained by subduction along the west coast of North America and destruction of the subduction system by development of the San Andreas transform fault system. However, re-analysis of space-time patterns of magmatism in western North America calls many of these inferred patterns of magmatism into question. Animation of space-time patterns found in the developing NAVDAT dataset (which currently hosts about 10,000 Cenozoic age and/or geochemical analyses; navdat.geongrid.org), demonstrates that: (1) subduction-type (e.g., intermediate) volcanism is poorly linked to the subduction system; (2) there is little evidence that slab windows controlled magmatism; (3) magmatism was clearly migratory, but not in ways that can be explained by plate-tectonic processes; and (4) magmatism was migratory at length scales ranging from 1000s of km (continental) to 10s of km (county). Several space-time patterns are evident in the NAVDAT animations, including: (1) a sweep from Montana into Nevada from 50 to about 20 Ma; (2) a clockwise sweep around the Colorado Plateau from New Mexico to southern Nevada, from about 30 to 15 Ma; (3) a burst of magmatism at about 16 Ma in northern Nevada, followed by outward sweeps to Yellowstone, central Oregon, and the Sierra Nevada; (4) a burst of magmatism in the Sierra Nevada at 3.5 Ma; and (5) several local migrations, including from Phoenix north onto the Colorado Plateau and from the San Francisco Bay area north to the Geysers geothermal field. Some of these patterns have been tied to specific events (e.g., impingement of the Yellowstone plume and Pliocene delamination), but the others are difficult to relate to plate-tectonic events. They may be caused by local tectonic events (propagating rifts?), minor convective rolls in the asthenosphere, lithospheric delamination, or delamination of a flat Laramide slab. Whatever their origin, database animation provides a powerful tool for examining these space-time patterns.
UR: http://navdat.geongrid.org
DE: 8499 General or miscellaneous
DE: 9350 North America
DE: 8099 General or miscellaneous
DE: 8110 Continental tectonics--general (0905)
DE: 8155 Plate motions--general
SC: Special Focus: Advances in Data Acquisition, Management, Analysis and Display [SF]
MN: 2004 AGU Fall Meeting