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| Titel |
Exhumation of (ultra-)high-pressure terranes: concepts and mechanisms |
| VerfasserIn |
C. J. Warren |
| 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 ; 4, no. 1 ; Nr. 4, no. 1 (2013-02-13), S.75-92 |
| Datensatznummer |
250017349
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| Publikation (Nr.) |
 copernicus.org/se-4-75-2013.pdf |
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| Zusammenfassung |
| The formation and exhumation of high and ultra-high-pressure, (U)HP, rocks
of crustal origin appears to be ubiquitous during Phanerozoic plate
subduction and continental collision events. Exhumation of (U)HP material
has been shown in some orogens to have occurred only once, during a single
short-lived event; in other cases exhumation appears to have occurred
multiple discrete times or during a single, long-lived, protracted event. It
is becoming increasingly clear that no single exhumation mechanism dominates
in any particular tectonic environment, and the mechanism may change in time
and space within the same subduction zone. Subduction zone style and
internal force balance change in both time and space, responding to changes
in width, steepness, composition of subducting material and velocity of
subduction. In order for continental crust, which is relatively buoyant
compared to the mantle even when metamorphosed to (U)HP assemblages, to be
subducted to (U)HP conditions, it must remain attached to a stronger and
denser substrate. Buoyancy and external tectonic forces drive exhumation,
although the changing spatial and temporal dominance of different driving
forces still remains unclear. Exhumation may involve whole-scale detachment
of the terrane from the subducting slab followed by exhumation within a
subduction channel (perhaps during continued subduction) or a reversal in
motion of the entire plate (eduction) following the removal of a lower part
of the subducting slab. Weakening mechanisms that may be responsible for the
detachment of deeply subducted crust from its stronger, denser substrate
include strain weakening, hydration, melting, grain size reduction and the
development of foliation. These may act locally to form narrow high-strain
shear zones separating stronger, less-strained crust or may act on the bulk
of the subducted material, allowing whole-scale flow. Metamorphic reactions,
metastability and the composition of the subducted crust all affect buoyancy
and overall strength. Future research directions include identifying
temporal and spatial changes in exhumation mechanisms within different
tectonic environments, and determining the factors that influence those
changes. |
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