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Subduction of aseismic oceanic ridges; effects on shape, seismicity, and other characteristics of consuming plate boundaries

P. R. Vogt, A. Lowrie, D. R. Bracey and R. N. Hey
Subduction of aseismic oceanic ridges; effects on shape, seismicity, and other characteristics of consuming plate boundaries
Special Paper - Geological Society of America (1976) (172): 59 pp.

Abstract

Aseismic ridges on underthrusting oceanic plates often trend into cusps or irregular indentations in the trace of the subduction zone. For example, the Hawaii-Emperor Ridge trends into the Kuril-Aleutian cusp, and the Marianas arc is bounded by the Marcus-Necker Ridge on the north and the Caroline Ridge on the south. The association between ridges and cusps is too common to be due to chance; it is proposed that the extra buoyancy of the plate with its aseismic ridge gives the plate greater resistance to sinking. This would inhibit back-arc extension and thereby produce a notch in the subduction zone. Island arcs may, therefore, acquire their curvature by additional constraints than the Earth"s curvature. The geology of about 15 such cusp areas is examined for evidence to test the hypothesis that cusps were caused by subducted aseismic ridges. This hypothesis applies only to cases where extensional basins lie behind the arcs. There also appear to be cases where the trace of the subduction zone has been modified not by inhibited back-arc spreading but by splintering of the overthrusting and possibly the underthrusting plate as well. Extremely high, massive aseismic ridges might induce arc polarity reversals and thereby assume the role of protocontinental nuclei. Seismicity and volcanism are examined where aseismic ridges are being subducted; there are several examples of reduced seismicity that cannot be explained by insufficient sampling time. By modifying the geometry of the subduction zone, the downgoing ridges necessarily affect seismicity. In addition, the plate containing the ridge may be thinner and hotter and more likely to deform by creep. There is no systematic increase or decrease in the number of andesite volcanoes where the ridges are subducted. However, lines of volcanoes and sometimes other kinds of geologic and seismic provinces may stop or start at the arc-ridge intersections. This is attributed to segmenting of the lithosphere into distinct tongues, each tongue acting more or less independently. Aseismic ridges would act as lines of weakness along which the downthrust slab becomes detached.


ISSN: 0072-1077
EISSN: 2331-219X
Coden: GSAPAZ
Serial Title: Special Paper - Geological Society of America
Serial Issue: 172
Title: Subduction of aseismic oceanic ridges; effects on shape, seismicity, and other characteristics of consuming plate boundaries
Author(s): Vogt, P. R.
Author(s): Lowrie, A.
Author(s): Bracey, D. R.
Author(s): Hey, R. N.
Affiliation: U. S. Nav. Oceanogr. Off., Wash., D.C., United States
Published: 1976
Text Language: English
Publisher: Geological Society of America (GSA), Boulder, CO, United States
ISBN: 978-0-81372-172-9
Number of pages: 59
Accession Number: 1976-036051
Categories: Solid-earth geophysics
Document Type: Serial
Bibliographic Level: Monographic
Illustration Description: illus. incl. sects., charts, sketch maps
N51°00'00" - N55°30'00", W161°00'00" - E172°00'00"
N09°00'00" - N22°00'00", W78°00'00" - W60°00'00"
S25°30'00" - S14°00'00", W87°30'00" - W76°00'00"
Secondary Affiliation: Univ. Tex. Mar. Sci. Inst., United States,
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2018, American Geosciences Institute.
Update Code: 1976
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