1 / 10

An inverted continental Moho and serpentinization of the forearc mantle

An inverted continental Moho and serpentinization of the forearc mantle. M.G. Bostock, R.D. Hyndman, S. Rondenay, and S.M. Peacock Presented by: Lauren Mattatall March 26, 2007. Intentions. To explore structure of the mantle wedge in the southern Cascadia subduction zone (CSZ)

weylin
Download Presentation

An inverted continental Moho and serpentinization of the forearc mantle

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. An inverted continental Moho and serpentinization of the forearc mantle M.G. Bostock, R.D. Hyndman, S. Rondenay, and S.M. Peacock Presented by: Lauren Mattatall March 26, 2007

  2. Intentions • To explore structure of the mantle wedge in the southern Cascadia subduction zone (CSZ) • To understand the observed variations in velocity structure in the forearc region

  3. Relief map of the CSZ White squares represent broadband stations Collected data from a dense broadband array of 69 stations across Central Oregon high-quality P-wave seismograms from 31 events Data Bostock et al., 2002

  4. Methods • 1) Applied formal, multichannel inversions of: • -forward scattered P to S wave conversions • -back-scattered waves caused by free surface reflections • 2) Plotted perturbations in velocity structure Bostock et al., 2002

  5. 3) Plotted a thermal model for Central Oregon -based on teleseismic profile, heat flow, and other geophysical data Note that the temperatures in the forearc are 400°-600° (200°-400° colder than arc temperatures) Methods Bostock et al., 2002

  6. Interpretations • Sharp increase in dip angle (from ~10° to ~30°) argues for eclogitization of the slab • Eclogitization implies hydration and serpentinization of the forearc • Thermal model temperatures are within the range that serpentine minerals are thought to be stable • With a high enough % composition, serpentinization of the forearc would significantly reduce S-wave velocities Bostock et al., 2002

  7. As presence of serpentinite increases, S-wave velocities decrease Observed S-wave velocities in the forearc indicate a possible composition of serpentinite as high as 50-60% Interpretations Bostock et al., 2002

  8. Interpretations Bostock et al., 2002

  9. Implications • Serpentine and it’s alteration products are though to exhibit stable sliding properties and will impede rupture into the forearc mantle • Mantle flow into the wedge may be modified by the presence of the serpentinized forearc mantle • The weak rheology and positive buoyancy will cause isolation from the mantle-wedge corner flow system

  10. Additional Thoughts... • To what depth are the perturbation plots reliable? • Are there other possible explanations for such a decreased velocity within the forearc?

More Related