Constraints on the composition of the Aleutian arc lower crust from VP/VS
Shillington, Donna J.
Van Avendonk, Harm J. A.
Behn, Mark D.
Kelemen, Peter B.
MetadataShow full item record
Determining the bulk composition of island arc lower crust is essential for distinguishing between competing models for arc magmatism and assessing the stability of arc lower crust. We present new constraints on the composition of high P-wave velocity (VP = 7.3–7.6 km/s) lower crust of the Aleutian arc from best-fitting average lower crustal VP/VS ratio using sparse converted S-waves from an along-arc refraction profile. We find a low VP/VS of ~1.7–1.75. Using petrologic modeling, we show that no single composition is likely to explain the combination of high VP and low VP/VS. Our preferred explanation is a combination of clinopyroxenite (~50–70%) and alpha-quartz bearing gabbros (~30–50%). This is consistent with Aleutian xenoliths and lower crustal rocks in obducted arcs, and implies that ~30–40% of the full Aleutian crust comprises ultramafic cumulates. These results also suggest that small amounts of quartz can exert a strong influence on VP/VS in arc crust.
Author Posting. © American Geophysical Union, 2013. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Geophysical Research Letters 40 (2013): 2579–2584, doi:10.1002/grl.50375.
Showing items related by title, author, creator and subject.
Drilling the oceanic lower crust and mantle : a global strategy for exploring the deep oceanic crust and mantle in the 1990's Workshop on Drilling the Oceanic Lower Crust and Mantle (Woods Hole Oceanographic Institution, 1989-03)This workshop was convened to follow up on the Second Conference on Scientific Ocean Drilling (COSOD II) to devise a specific plan for deep crustal and mantle drilling over the next decade. Since COSOD II, however, there ...
Plagioclase preferred orientation in layered mylonites : evaluation of flow laws for the lower crust Mehl, Luc; Hirth, Greg (American Geophysical Union, 2008-05-07)We evaluate the applicability of plagioclase and gabbro flow laws by comparing predicted and observed deformation mechanisms in gabbroic shear zones. Gabbros and layered gabbro mylonites were collected from the Southwest ...
Plagioclase preferred orientation in layered mylonites : evaluation of flow laws for the lower crust Mehl, Luc (Massachusetts Institute of Technology and Woods Hole Oceanographic Institution, 2008-02)We evaluate the applicability of plagioclase and gabbro flow laws by comparing predicted and observed deformation mechanisms in gabbroic shear zones. Gabbros and layered gabbro mylonites were collected from the Southwest ...