Subduction Tectonics/Active Margin Evolution
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Transcript of Subduction Tectonics/Active Margin Evolution
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Subduction Tectonics/Active Margin Evolution
Peter Clift
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Philippine Sea Plate, Subduction Initiation
Casey and Dewey (1984)
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Bloomer et al. (1995)
Subduction Initiation
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Initiation at a fracture zone
Casey and Dewey (1984)
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Collapse at the ridge crest?
Callovian; 166 MaAsymmetric ridge collapseMetamorphic sole formed
Late Callovian-Oxfordian; 163 MaSupra-subduction spreading Boninite volcanism
Vourinos & PindosOphiolites
Ophiolite obduction
Kimmeridgian; 153 MaMigdhalitsa & OthrisOphiolites
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Forces that resist subduction initiation
McKenzie, 1977
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Flow of asthenosphere into a crack?
Turcotte et al. (1977)
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Boninites
Pearce and Parkinson (1993)
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Metamorphic soles
Jones et al. (1991)Pindos Mountains, Greece
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Anatomy of an intra-oceanic arc
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Subduction seismicity
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Subduction polarity flip
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Aegean Seismicity- backarc extension
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Angle of descent, controling factors?
Isacks and Molnar (1971)
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Stresses in the descending slab.
Isacks and Molnar (1969)
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Backarc rifting-Izu-Bonin Arc
(B) Extension of the arc
Flow of depletedupper mantle
Basinal basaltic volcanism and voluminous high silica volcanic centers
(D) Spreading starts on backarc spreading center. New Arc begins activity
Subsiding forearc
low-K tholeiites
Rifted arc basement ?
(A) Steady state subduction
Forearc Basin
(C) Continued extension and seamount volcanism
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Backarc rifting-Tonga: location of rift axis?
(B) Extension of the arc
Flow of depletedupper mantle
Basinal basaltic volcanism and voluminous high silica volcanic centers
(D) Spreading starts on backarc spreading center. New Arc begins activity
Subsiding forearc
Minor alkalibasalts and Hawaiites
low-K tholeiites
Rifted arc basement ?
(A) Steady state subduction
Forearc Basin
(C) Continued extension and seamount volcanism
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Magmatic variations during backarc rifting
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En-echelon spreading axes, Havre Trough
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Rift-drift transition in backarcs
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Propagating rifts in backarc basins
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Hydrothermalism in backarc basins
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Different basement types and styles of hydrothermalism
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Effect of seamount collision on arc magmatism. Magmatic gap?
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Subduction erosion in
Tonga.
120
100
80
60
40
20
0
0 10 20 30 40
Age (Ma)
B
-20
A
-2
0
2
4
6
8
0 10 20 30 40
Arcwardtilting
Trenchwardtilting
?
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Tonga Forearc Subsidence
.
0
-1
1
2
3
4
6
Age (Ma)0 10 20 30 40 50
Oceaniccrust
Modern depthMinimum subsidencerelated to crustalthinning
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Perched basins on an erosive plate margin
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Tonga fore-arc trench slope basin.
E
5.5
6.0
1 km
W
1
2
3
4
1
1
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Paired metamorphic belts