pure and applied geophysics

, Volume 128, Issue 3, pp 455–500

Subduction-channel model of prism accretion, melange formation, sediment subduction, and subduction erosion at convergent plate margins: 1. Background and description

  • Mark Cloos
  • Ronald L. Shreve
Article

DOI: 10.1007/BF00874548

Cite this article as:
Cloos, M. & Shreve, R.L. PAGEOPH (1988) 128: 455. doi:10.1007/BF00874548
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Abstract

Many geological and geophysical investigations, particularly the Deep Sea Drilling Project, have shown that convergent plate margins are highly diverse features. For example, at some sites of subduction, such as the Lesser Antilles, the bedded sediment atop the incoming oceanic plate is extensively offscraped, whereas at others, such as Mariana, not only is the incoming sediment completely subducted beneath crystalline rock but portions of the overriding plate are undergoing subduction erosion. Earthquakes indicate wide variations in stress distribution within and between sites of plate convergence. Many ancient accretionary complexes include tracts of intensely-deformed subduction melange that contain blocks of mafic greenstones. Some contain bodies of thoroughly recrystallized blueschist that were uplifted from depths of 20 to 30 km. A comprehensive model for convergent plate margins must explain these and numerous other observations. Although the still widely cited imbricatethrust model for prism accretion qualitatively explains some observations at subduction zones, it does not account for many others, such as deep sediment subduction and subduction erosion.

The subduction-channel model postulates essentially the same basic mechanics for all convergent plate margins that have attained a quasi-steady state (typically reached after about 20 Ma of subduction at speeds of 10 to 20 km Ma−1). It assumes that the subducting sediment deforms approximately as a viscous material once it is dragged into a relatively thin shear zone, or subduction channel, between the downgoing plate and the overriding one. It predicts the overall movement patterns of the sediment deforming within the channel and near its inlet, accounts for most of the observed features at convergent plate margins, and quantifies the processes of sediment subduction, offscraping, and underplating, and the formation of subduction melange. The predicted variations in tectonic behavior depend upon such site-specific variables as the speed of subduction, the supply of sediment, the geometry of the descending plate, and the topography and structure of the overriding block.

Key words

Subduction zonesubduction accretionsubduction erosionsediment subductionaccretionary prismmelangeoffscrapingunderplating

Copyright information

© Birkhäuser Verlag 1988

Authors and Affiliations

  • Mark Cloos
    • 1
  • Ronald L. Shreve
    • 2
  1. 1.Department of Geological Sciences and Institute for GeophysicsUniversity of Texas at AustinAustinUSA
  2. 2.Department of Earth and Space Sciences and Institute of Geophysics and Planetary PhysicsUniversity of CaliforniaLos AngelesUSA