The 'subduction initiation rule': A key for linking ophiolites, intra-oceanic forearcs, and subduction initiation

Scott A. Whattam, Robert J. Stern

Research output: Contribution to journalArticle

169 Citations (Scopus)

Abstract

We establish the 'subduction initiation rule' (SIR) which predicts that most ophiolites form during subduction initiation (SI) and that the diagnostic magmatic chemostratigraphic progression for SIR ophiolites is from less to more HFSE-depleted and LILE-enriched compositions. This chemostratigraphic evolution reflects formation of what ultimately becomes forearc lithosphere as a result of mantle melting that is progressively influenced by subduction zone enrichment during SI. The magmatic chemostratigraphic progression for the Izu-Bonin-Mariana (IBM) forearc and most Tethyan ophiolites is specifically from MORB-like to arc-like (volcanic arc basalts or VAB ± boninites or BON) because SI progressed until establishment of a mature subduction zone. MORB-like lavas result from decompression melting of upwelling asthenosphere and are the first magmatic expression of SI. The contribution of fluids from dehydrating oceanic crust and sediments on the sinking slab is negligible in early SI, but continued melting results in a depleted, harzburgitic residue that is progressively metasomatized by fluids from the sinking slab; subsequent partial melting of this residue yields 'typical' SSZ-like lavas in the latter stages of SI. If SI is arrested early, e.g., as a result of collision, 'MORB-only' ophiolites might be expected. Consequently, MORB- and SSZ-only ophiolites may represent end-members of the SI ophiolite spectrum. The chemostratigraphic similarity of the Mariana forearc with that of ophiolites that follow the SIR intimates that a model linking such ophiolites, oceanic forearcs, and SI is globally applicable.

Original languageEnglish
Pages (from-to)1031-1045
Number of pages15
JournalContributions to Mineralogy and Petrology
Volume162
Issue number5
DOIs
Publication statusPublished - 2011 Nov 1
Externally publishedYes

Fingerprint

Melting
subduction
mid-ocean ridge basalt
Fluids
melting
Sediments
sinking
subduction zone
slab
progressions
Chemical analysis
slabs
arcs
fluid
asthenosphere
decompression
ophiolite
fluids
pressure reduction
upwelling water

Keywords

  • Forearcs
  • Intra-oceanic arcs
  • Izu-Bonin-Marianas arc
  • Ophiolites
  • Subduction initiation
  • Tethys

ASJC Scopus subject areas

  • Geochemistry and Petrology
  • Geophysics

Cite this

The 'subduction initiation rule' : A key for linking ophiolites, intra-oceanic forearcs, and subduction initiation. / Whattam, Scott A.; Stern, Robert J.

In: Contributions to Mineralogy and Petrology, Vol. 162, No. 5, 01.11.2011, p. 1031-1045.

Research output: Contribution to journalArticle

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