Strength and survival of subducted lithosphere during the Laramide orogeny
- Arizona Geological Survey, Tucson, AZ (United States)
The strength of subducted ocean lithosphere is influenced primarily by two competing processes. During subduction brittle rock strength increases because of increasing compressive stress across fracture surfaces which increases frictional resistance to sliding. The strength of rocks hot enough to be in the plastic deformation regime decreases primarily because of heat conducted from the overriding plate and the asthenosphere. A one-dimensional finite-element heat-flow program was used to simulate subduction in two dimensions where conductive heat flow parallel to the slab and to the upper plate could be neglected. Temperatures determined with this method, and pressures based on depth, were then used to calculate the form of the brittle-plastic failure envelope for subducted lithosphere. An olivine flow law and strain rate of 10[sup [minus]15] s[sup [minus]1] were used for the plastic part of the failure envelope. The failure envelope was then used to calculate slab-parallel compressive strength and maximum sustainable bending moment. Modeling of Maramide subduction beneath southwestern North America, using slab ages and subduction rates for the Farallon plate from Engebretson et al., suggests that the subducted slab will not retain much strength beyond 1,000 to 1,200 km inland unless the thickness of the North American lithosphere, and depth to the top of the slab, are significantly less than 200 km. Slab survival for distances of 1000 km seems assured. Survival for much greater distances is possible. The slab is predicted to have been up to several times stronger beneath southwestern North America than at the trench because much rock remains in the brittle regime and is under high confining pressure.
- OSTI ID:
- 5023538
- Report Number(s):
- CONF-9305259-; CODEN: GAAPBC
- Journal Information:
- Geological Society of America, Abstracts with Programs; (United States), Vol. 25:5; Conference: 89. annual meeting of the Cordilleran Section and the 46th annual meeting of the Rocky Mountain Section of the Geological Society of America (GSA), Reno, NV (United States), 19-21 May 1993; ISSN 0016-7592
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
ARIZONA
SUBDUCTION ZONES
CALIFORNIA
NEVADA
GEOLOGIC MODELS
GEOLOGY
COMPRESSION STRENGTH
CRETACEOUS PERIOD
DEFORMATION
DUCTILE-BRITTLE TRANSITIONS
GEOLOGIC HISTORY
HEAT FLOW
OCEANIC CRUST
OROGENESIS
PLASTICITY
PLATE TECTONICS
ROCK MECHANICS
TERTIARY PERIOD
TWO-DIMENSIONAL CALCULATIONS
CENOZOIC ERA
DEVELOPED COUNTRIES
EARTH CRUST
GEOLOGIC AGES
MECHANICAL PROPERTIES
MECHANICS
MESOZOIC ERA
NORTH AMERICA
TECTONICS
USA
580000* - Geosciences