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| Titel |
Future accreted terranes: a compilation of island arcs, oceanic plateaus, submarine ridges, seamounts, and continental fragments |
| VerfasserIn |
J. L. Tetreault, S. J. H. Buiter |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1869-9510
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| Digitales Dokument |
URL |
| Erschienen |
In: Solid Earth ; 5, no. 2 ; Nr. 5, no. 2 (2014-12-04), S.1243-1275 |
| Datensatznummer |
250115355
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| Publikation (Nr.) |
 copernicus.org/se-5-1243-2014.pdf |
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| Zusammenfassung |
| Allochthonous accreted terranes are exotic geologic units that originated
from anomalous crustal regions on a subducting oceanic plate and were
transferred to the overriding plate by accretionary
processes during subduction. The geographical regions that eventually become accreted
allochthonous terranes include island arcs, oceanic plateaus, submarine
ridges, seamounts, continental fragments, and microcontinents. These future
allochthonous terranes (FATs) contribute to continental crustal growth,
subduction dynamics, and crustal recycling in the mantle. We present a review
of modern FATs and their accreted counterparts based on available geological,
seismic, and gravity studies and discuss their crustal structure, geological
origin, and bulk crustal density. Island arcs have an average crustal
thickness of 26 km, average bulk crustal density of 2.79 g cm−3, and three distinct crustal units overlying a crust–mantle transition zone.
Oceanic plateaus and submarine ridges have an average crustal thickness of 21
km and average bulk crustal density of 2.84 g cm−3. Continental
fragments presently on the ocean floor have an average crustal thickness of
25 km and bulk crustal density of 2.81 g cm−3. Accreted allochthonous
terranes can be compared to these crustal compilations to better understand
which units of crust are accreted or subducted. In general, most accreted
terranes are thin crustal units sheared off of FATs and added onto the
accretionary prism, with thicknesses on the order of hundreds of meters to a
few kilometers. However, many island arcs, oceanic plateaus, and submarine
ridges were sheared off in the subduction interface and underplated onto the
overlying continent. Other times we find evidence of terrane–continent
collision leaving behind accreted terranes 25–40 km thick. We posit that
rheologically weak crustal layers or shear zones that were formed when the
FATs were produced can be activated as detachments during subduction,
allowing parts of the FAT crust to accrete and others to subduct. In many
modern FATs on the ocean floor, a sub-crustal layer of high seismic
velocities, interpreted as ultramafic material, could serve as a detachment
or delaminate during subduction. |
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