Characterization of lithospheric mantle of West Antarctica using mantle xenoliths from 1.4 Ma basalts of the Fosdick Mountains: Proposed research and preliminary results
Abstract
Marie Byrd Land (MBL), West Antarctica, supports the West Antarctic Ice Sheet and is noted for having active volcanism, a regional thermal anomaly measured by the Gravity Recovery and Climate Experiment (GRACE) satellite, and slow seismic velocities within underlying mantle. A means to test the competing hypotheses for the origin of these anomalies is offered by abundant mantle xenoliths entrained in basalts of ca. 1.4 Ma in the Fosdick Mountains. Seven volcanic centers, known from prior research to derive from heterogeneous mantle sources, host a compositionally diverse suite of mantle xenoliths that have varied mineral assemblages and microstructures. Now in its early stages, our quantitative investigation of intrinsic (composition, grain size, crystallographic texture) and extrinsic (P-T, strain rate, σ, fO2) variables may be used for direct characterization of lithospheric mantle of West Antarctica that has been subject to active modification from Cretaceous to Present by plate-boundary processes, including orthogonal to oblique plate convergence, intracontinental rifting, continental breakup, and Neogene volcanism. We employ techniques and draw upon findings obtained from prior research to achieve a characterization of (1) shape preferred orientation (SPO) of phases; (2) crystallographic (lattice) preferred orientation (LPO) from EBSD; and (3) water contents for major phases from FTIR spectroscopy to provide critical new information about the structural and compositional heterogeneity of the upper mantle, and the contrasting thermal and chemical histories of West Antarctic lithosphere that have bearing on the modeling of solid earth geodynamic response to ice mass changes. An aim is to provide a type of "ground truth" in support of ANET/POLENET seismology research in West Antarctica that seeks to determine mantle composition, temperature, and sources of seismic anisotropy. Measurements of LPO and SPO, complemented by geothermobarometry and water content determinations will allow seismologists to refine the interpretations of anisotropy and body-wave data from regional and teleseismic earthquakes recorded by broadband seismic instruments in the ANET/POLENET array.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2012
- Bibcode:
- 2012AGUFM.T41B2586K
- Keywords:
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- 1212 GEODESY AND GRAVITY / Earth's interior: composition and state;
- 1236 GEODESY AND GRAVITY / Rheology of the lithosphere and mantle;
- 8120 TECTONOPHYSICS / Dynamics of lithosphere and mantle: general;
- 8159 TECTONOPHYSICS / Rheology: crust and lithosphere