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.
Suggested CitationGeochemistry Geophysics Geosystems 5 (2004): Q10006
Showing items related by title, author, creator and subject.
Globally elevated titanium, tantalum, and niobium (TITAN) in ocean island basalts with high 3He/4He Jackson, Matthew G.; Hart, Stanley R.; Saal, Alberto E.; Shimizu, Nobumichi; Kurz, Mark D.; Blusztajn, Jerzy S.; Skovgaard, Anna C. (American Geophysical Union, 2008-04-17)We report evidence for a global Ti, Ta, and Nb (TITAN) enriched reservoir sampled by ocean island basalts (OIBs) with high 3He/4He ratios, an isotopic signature associated with the deep mantle. Excesses of Ti (and to a ...
The Wrangel Island Polynya in early summer : trends and relationships to other polynyas and the Beaufort Sea High Moore, G. W. K.; Pickart, Robert S. (American Geophysical Union, 2012-03-15)Polynyas, regions of reduced sea ice concentration relative to their surroundings, are important features of the polar climate system in which enhanced fluxes of heat, moisture, and momentum can occur between the atmosphere ...
Wallace, Elizabeth J.; Donnelly, Jeffrey P.; van Hengstum, Peter J.; Wiman, Charlotte; Sullivan, Richard M.; Winkler, Tyler S.; D'Entremont, Nicole; Toomey, Michael R.; Albury, Nancy A. (American Geophysical Union, 2019-10-19)Hurricanes cause substantial loss of life and resources in coastal areas. Unfortunately, historical hurricane records are too short and incomplete to capture hurricane‐climate interactions on multi‐decadal and longer ...