Fate of the Cenozoic Farallon slab from a comparison of kinematic thermal modeling with tomographic images

Christian Schmid*, Saskia Goes, Suzan Van der Lee, Domenico Giardini

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

45 Scopus citations

Abstract

After more than 100 million years of subduction, only small parts of the Farallon plate are still subducting below western North America today. Due to the relatively young age of the most recently subducted parts of the Farallon plate and their high rates of subduction, the subducted lithosphere might be expected to have mostly thermally equilibrated with the surrounding North American mantle. However, images from seismic tomography show positive seismic velocity anomalies, which have been attributed to this subduction, in both the upper and lower mantle beneath North America. We use a three-dimensional kinematic thermal model based on the Cenozoic plate tectonic history to quantify the thermal structure of the subducted Farallon plate in the upper mantle and determine which part of the plate is imaged by seismic tomography. We find that the subducted Farallon lithosphere is not yet thermally equilibrated and that its thermal signature for each time of subduction is found to be presently detectable as positive seismic velocity anomalies by tomography. However, the spatially integrated positive seismic velocity anomalies in tomography exceed the values obtained from the thermal model for a rigid, continuous slab by a factor of 1.5 to 2.0. We conclude that Farallon fragments that subducted since 50 to 60 Ma are still residing in the upper mantle and must be heavily deformed. The deformation of the slab in the transition zone is probably caused by the same mechanisms that were responsible for flat subduction around 60 Ma.

Original languageEnglish (US)
Pages (from-to)17-32
Number of pages16
JournalEarth and Planetary Science Letters
Volume204
Issue number1-2
DOIs
StatePublished - Nov 30 2002

Keywords

  • Farallon plate
  • Subduction
  • Thermo-kinematic modeling
  • Tomography
  • Upper mantle

ASJC Scopus subject areas

  • Geophysics
  • Geochemistry and Petrology
  • Earth and Planetary Sciences (miscellaneous)
  • Space and Planetary Science

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