April 7 @ 12:00 pm - 12:50 pm CDT
Who: Gary Linkevich & Proteek Chowdhury
When: Noon, Friday, April 7, 2017
Where: Room 100, KWGL
Linkevich “3D Seismic Observations of the Peridotite Ridge in the Deep Galicia Margin”
The west coast of the Iberian Peninsula is a classic magma-poor rifted margin, where slow crustal hyperextension allowed the mantle rising beneath to cool and harden, instead of melting. The boundary between the last crustal blocks and this transitional zone of exhumed mantle is marked by a long, margin-parallel peridotite ridge (PR). Over the past few decades, this PR was dredged, cored, and imaged in several 2D seismic surveys. These efforts documented its regional extent and thorough serpentinization, but offered limited insight into its internal structure. And while several hypotheses have evolved regarding the PR’s origin, there is no consensus, and almost no discussion of its post-emplacement evolution. Finally, there are major uncertainties not just within the PR, but in the jumbled-up material surrounding it.
The recently-acquired Galicia3D seismic dataset reveals several internal structures within the PR, including a large landward-dipping normal fault cleaving off its eastern flank, and a continuous internal boundary separating a reflective, chaotic upper layer from a more homogeneous core. The eastern fault dives to at least 10 s TWT, and is hypothesized to restore in some way to the S detachment fault in the east. It also appears to continue into the post-rift sediments overlying the PR, offsetting material up to 100 myr younger than the PR itself. The reflective upper layer of the PR may represent the extent of its serpentinization, but could also include a variety of prerift or synrift material.
On the surface of the PR, the western flank contains several arcuate, scoop-like scarps that correspond to substantial mass wasting events. A similar feature on the eastern flank has been mapped in 3D, and display deformational structures usually observed in mass transport deposits on land. However the PR achieved its distinctive shape, the processes involved have broad implications on the timing and evolution of the margin as a whole.
Chowdhury: “Effect of sulfate on the liquidus and Sulfur Concentration at Anhydrite Saturation (SCAS) of hydrous basalt at Subduction Zones”