SGER: Seismic Study of Deep Eclogitic-Granulitic Crust and Moho

University Of Wyoming, Laramie WY

Investigators

Abstract

Seismic Study of Deep Eclogitic Crust and Moho Scott Smithson University of Wyoming Abstract This is a Small Grant for Exploratory Research proposal for a seismic data acquisition program that has suddenly become possible because of a change in schedule of a marine research vessel. The SGER proposal appears to be the only way that we can respond to this opportunity in its time frame. One of the classic eclogite localities is in the Bergen Arcs of western Norway where eclogitization is related to fluid flow along shear zones in granulites. What is the nature of continental crust beneath an eclogite terrain, where did the eclogites come from, and how did they get there? These are the problems that we proposal to clarify. We have an exciting "target-of-opportunity" to conduct detailed marine-land seismic reflection/refraction profiling over this eclogite locality in the Bergen Arcs of Norway. We have been developing this project over the last two years in cooperation with Professor Rolf Mjelde of the University of Bergen, based on his knowledge of the area and use of the University of Bergen research vessel for the seismic profiling. Typical of marine research vessels, this one has a full schedule, planned years in advance, so that 2004 seemed to be the first year to work our project into the schedule. Now on occasion of activating a new research vessel, we have just learned that we have 7 days of ship time for this eclogite project in May of 2003. We propose a program of combined marine-land recording firing marine airguns into 15-20 OBS's and 15 Refteks with 3-component sensors that personnel from the University of Wyoming will set up on land, generating a highly detailed, complete data set with close trace spacing. The striking characteristics of this type of recording are close trace spacing over long distances and spectacular S-waves from P-wave conversion at the ocean bottom. These clear S-wave onsets provide additional constraints in Vp/Vs and S-wave splitting. Combination of Vp, Vs, Vp/Vs and imaging major faults, Moho, and larger eclogite bodies should provide new, important seismic constraints on the distribution of eclogite in the deep crust, provenance of the eclogitic thrust sheet, nature of the Moho, and possibly fluid pathways