Subduction Tectonics/Active Margin Evolution

Peter Clift

Philippine Sea Plate, Subduction Initiation

Casey and Dewey (1984)

Bloomer et al. (1995)

Subduction Initiation

Initiation at a fracture zone

Casey and Dewey (1984)

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

Forces that resist subduction initiation

McKenzie, 1977

Flow of asthenosphere into a crack?

Turcotte et al. (1977)

Boninites

Pearce and Parkinson (1993)

Metamorphic soles

Jones et al. (1991)Pindos Mountains, Greece

Anatomy of an intra-oceanic arc

Subduction seismicity

Subduction polarity flip

Aegean Seismicity- backarc extension

Angle of descent, controling factors?

Isacks and Molnar (1971)

Stresses in the descending slab.

Isacks and Molnar (1969)

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

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

Magmatic variations during backarc rifting

En-echelon spreading axes, Havre Trough

Rift-drift transition in backarcs

Propagating rifts in backarc basins

Hydrothermalism in backarc basins

Different basement types and styles of hydrothermalism

Effect of seamount collision on arc magmatism. Magmatic gap?

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

?

Tonga Forearc Subsidence

.

0

-1

1

2

3

4

6

Age (Ma)0 10 20 30 40 50

Oceaniccrust

Modern depthMinimum subsidencerelated to crustalthinning

Perched basins on an erosive plate margin

Tonga fore-arc trench slope basin.

E

5.5

6.0

1 km

W

1

2

3

4

1

1

Paired metamorphic belts