Journal article
To understand subduction initiation, study forearc crust; to understand forearc crust, study ophiolites
Lithosphere, Vol.4(6), pp.469-483
05/16/2012
DOI: 10.1130/L183.1
Abstract
Articulating a comprehensive plate-tectonic theory requires understanding how new subduction zones form (subduction initiation). Because subduction initiation is a tectonomagmatic singularity with few active examples, reconstructing subduction initiation is challenging. The lithosphere of many intra-oceanic forearcs preserves a high-fidelity magmatic and stratigraphic record of subduction initiation. We have heretofore been remarkably ignorant of this record, because the "naked forearcs" that expose subduction initiation crustal sections are distant from continents and lie in the deep trenches, and it is difficult and expensive to study and sample this record via dredging, diving, and drilling. Studies of the Izu-Bonin-Mariana convergent margin indicate that subduction initiation there was accompanied by seafloor spreading in what ultimately became the forearc of the new convergent margin. Izu-Bonin-Mariana subduction initiation encompassed approximately 7 m.y. for the complete transition from initial seafloor spreading and eruption of voluminous mid-ocean-ridge basalts (forearc basalts) to normal arc volcanism, perhaps consistent with how long it might take for slowly subsiding lithosphere to sink approximately 100 km deep and for mantle motions to evolve from upwelling beneath the infant arc to downwelling beneath the magmatic front. Many ophiolites have chemical features that indicate formation above a convergent plate margin, and most of those formed in forearcs, where they were well positioned to be tectonically emplaced on land when buoyant crust jammed the associated subduction zone. We propose a strategy to better understand forearcs and thus subduction initiation by studying ophiolites, which preserve the magmatic stratigraphy, as seen in the Izu-Bonin-Mariana forearc; we call these "subduction initiation rule" ophiolites. This understanding opens the door for on-land geologists to contribute fundamentally to understanding subduction initiation.
Details
- Title: Subtitle
- To understand subduction initiation, study forearc crust; to understand forearc crust, study ophiolites
- Creators
- R. J Stern - The University of Texas at DallasM Reagan - University of IowaO Ishizuka - National Institute of Advanced Industrial Science and TechnologyY Ohara - Hydrographic and Oceanographic Department of Japan, Tokyo 104-0045, JapanS Whattam - Korea University
- Contributors
- John Wakabayashi (Editor)John W Shervais (Editor)
- Resource Type
- Journal article
- Publication Details
- Lithosphere, Vol.4(6), pp.469-483
- Publisher
- Geological Society of America
- DOI
- 10.1130/L183.1
- ISSN
- 1941-8264
- eISSN
- 1947-4253
- Number of pages
- 16
- Alternative title
- Initiation and termination of subduction; rock record, geodynamic models, and modern plate boundaries
- Language
- English
- Date published
- 05/16/2012
- Academic Unit
- Earth and Environmental Sciences
- Record Identifier
- 9984229163002771
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