BEG/JSG: Postdoctoral Fellow Collaborative Seminar
||May 15, 2015 at 9:00 am
||May 15, 2015 at 10:00 am|
| ||Location:||BEG Main Conference Room; Building 130; PRC Campus|
| ||Contact:||Sophia Ortiz, firstname.lastname@example.org, 512.475.9588|
| ||URL:||Event Link|
Jackson School of Geological Sciences Speakers:
Reactive transport and flow in porous media: an example from the mantle at Trinity ophiolite
Presented by: Nick Dygert (9:00-9:20)
Tabular dunite bodies (dunite channels) are thought to represent pathways for efficient melt extraction from the mantle. They form by melt-rock reaction, an important physical process that affects the compositions of dunite-hosted basaltic melts and the mantle they originate from. In order to better understand melt-rock interactions at dunite channels, we analyzed pyroxene in samples collected across an ~20 m wide dunite-harzburgite-lherzolite-plagioclase lherzolite sequence at the Trinity Ophiolite. The lithological sequence and major and trace element concentration gradients suggest a two stage history of evolution is preserved at Trinity. In the first stage, basaltic melt infiltrated a harzburgitic residue of partial melting, forming plagioclase lherzolite. In the second stage, a trace element depleted melt migrated from a dunite channel into the plagioclase lherzolite. The infiltration of dunite-hosted melts into peridotitic host rock may be common, providing an explanation for the wide array of melt-peridotite interactions observed in abyssal peridotites and some ophiolites.
A tale of two projects: Pliocene drivers of erosion in the Andes and the fate of Deepwater Horizon oil
Presented by: George Fisher (9:20-9:40)
The aim of this talk is to briefly showcase two of the projects I am currently working on as well as highlight some of the techniques I use in my research. I will begin by discussing ongoing work in NW Argentina where we have utilized a unique field setting along the foreland Rio Iruya canyon to create a high-resolution terrestrial record of erosion rates off the eastern Cordillera spanning the Pliocene. Early evidence indicates a strong correlation between erosion rate values and 400 kyr eccentricity driven insolation and may result from complex global climate teleconnections. The second part of the talk will focus on recent and ongoing work in the Gulf of Mexico looking at the fate and degradation of the oil released during the 2010 Deepwater Horizon oil spill. Our work identifies a fallout plume of hydrocarbons ~3200 km2 in area on the seafloor surrounding the spill site and represents ~4-30% of the oil sequestered in the deep ocean (~2 million barrels). I will end by highlighting some of the implications, questions, and ongoing research directions associated with this finding.
Spatial-temporal changes in seismic attenuation indicate the movement of sequestrated CO2
Presented by: Tieyuan Zhu (9:40-10:00)
Active source crosswell seismic data was continuously collected during CO2 injection in Frio CO2 sequestration site in Texas. I present an analysis of spatial-temporal seismic attenuation changes of the first P-wave arrivals. Attenuation changes over the injection period are estimated by the amount of the centroid frequency shift computed by the local frequency tool. Observations are: at receivers above the packer (in shale) seismic attenuation does not change in a physical trend; at receivers below the packer (in Frio formation) attenuation sharply increases as the amount of CO2 plume increase and peaks at specific points with distributed receivers, which are consistent with observations from time delays of first arrivals. Then, attenuation decreases over the injection time with increased amount of CO2 plume. Attenuation changes show a unique increase-decrease pattern. Along with the attenuation-saturation White patchy model, the relationship between increase-decrease pattern of attenuation change and CO2 saturation can be (at least) qualitatively explained. Our analysis suggests that seismic attenuation during CO2 injection not only is able to reveal the movement/saturation of CO2 plume but also is sensitive to a possible larger saturation that velocity does not.