Composition and structure of the central Aleutian island arc from arc-parallel wide-angle seismic data
Shillington, Donna J.
Van Avendonk, Harm J. A.
Holbrook, W. Steven
Kelemen, Peter B.
Hornbach, Matthew J.
MetadataShow full item record
New results from wide-angle seismic data collected parallel to the central Aleutian island arc require an intermediate to mafic composition for the middle crust and a mafic to ultramafic composition for the lower crust and yield lateral velocity variations that correspond to arc segmentation and trends in major element geochemistry. The 3-D ray tracing/2.5-D inversion of this sparse wide-angle data set, which incorporates independent phase interpretations and new constraints on shallow velocity structure, produces a faster and smoother result than a previously published velocity model. Middle-crustal velocities of 6.5–7.3 km/s over depths of ∼10–20 km indicate an andesitic to basaltic composition. High lower-crustal velocities of 7.3–7.7 km/s over depths of ∼20–35 km are interpreted as ultramafic-mafic cumulates and/or garnet granulites. The total crustal thickness is 35–37 km. This result indicates that the Aleutian island arc has higher velocities, and thus more mafic compositions, than average continental crust, implying that significant modifications would be required for this arc to be a suitable building block for continental crust. Lateral variations in average crustal velocity (below 10 km) roughly correspond to trends in major element geochemistry of primitive (Mg # > 0.6) lavas. The highest lower-crustal velocities (and presumably most mafic material) are detected in the center of an arc segment, between Unmak and Unalaska Islands, implying that arc segmentation exerts control over crustal composition.
Author Posting. © American Geophysical Union, 2004. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Geochemistry Geophysics Geosystems 5 (2004): Q10006, doi:10.1029/2004GC000715.
Showing items related by title, author, creator and subject.
Complexities in barrier island response to sea level rise : insights from numerical model experiments, North Carolina Outer Banks Moore, Laura J.; List, Jeffrey H.; Williams, S. Jeffress; Stolper, David (American Geophysical Union, 2010-07-09)Using a morphological-behavior model to conduct sensitivity experiments, we investigate the sea level rise response of a complex coastal environment to changes in a variety of factors. Experiments reveal that substrate ...
Wetland-estuarine-shelf interactions in the Plum Island Sound and Merrimack River in the Massachusetts coast Zhao, Liuzhi; Chen, Changsheng; Vallino, Joseph J.; Hopkinson, Charles S.; Beardsley, Robert C.; Lin, Huichan; Lerczak, James A. (American Geophysical Union, 2010-10-16)Wetland-estuarine-shelf interaction processes in the Plum Island Sound and Merrimack River system in the Massachusetts coast are examined using the high-resolution unstructured grid, finite volume, primitive equations, ...
Intermediate to felsic middle crust in the accreted Talkeetna arc, the Alaska Peninsula and Kodiak Island, Alaska : an analogue for low-velocity middle crust in modern arcs Rioux, Matthew; Mattinson, James; Hacker, Bradley R.; Kelemen, Peter B.; Blusztajn, Jerzy S.; Hanghoj, Karen; Gehrels, George (American Geophysical Union, 2010-05-08)Seismic profiles of several modern arcs have identified thick, low-velocity midcrustal layers (Vp = 6.0–6.5 km/s) that are interpreted to represent intermediate to felsic plutonic crust. The presence of this silicic crust ...