Continental Collision and the STEP-wise Evolution of Convergent Plate Boundaries: From Structure to Dynamics

2009 ◽  
pp. 47-59 ◽  
Author(s):  
Rinus Wortel ◽  
Rob Govers ◽  
Wim Spakman
Keyword(s):  
Continental Collision ◽  
Plate Boundaries ◽  
Convergent Plate Boundaries

Experimental investigation of antigorite dehydration fabrics at high pressure and high temperature

2020 ◽  
Author(s):  
Junfeng Zhang ◽  
Wenlong Liu ◽  
Yongfeng Wang
Keyword(s):  
Mantle Wedge ◽  
Seismic Anisotropy ◽  
Coarse Grained ◽  
Anisotropic Fluid ◽  
Plate Boundaries ◽  
Intermediate Depth ◽  
Fine Grained ◽  
Serpentinized Peridotite ◽  
Type C ◽  
Convergent Plate Boundaries

<p>Antigorite dehydration is well known as a key process in convergent boundaries for the genesis of mantle wedge partial melting and intermediate-depth earthquakes. However, the crystallographic preferred orientations (CPOs) of prograde minerals from antigorite dehydration and its effects on seismic anisotropy of subducting slabs remain ambiguous and controversial. Here we report hydrostatic dehydration experiments on foliated serpentinized peridotite at pressures of 0.3-6 GPa and temperatures of 700-900 °C. Our results show that the orientations of prograde olivine inherit orientations from adjacent olivine grains in the olivine-rich layer by epitaxial growth. In contrast, olivine CPOs evolved with the grain size from fiber-[001] featuring clear [100] point maxima and [001] girdles for fine-grained olivine to orthorhombic patterns characterized by clear [100] and [001] point maxima for coarse-grained olivine, i.e., type-C CPO. We propose that the fine-grained fiber-[001] CPO is developed by topotactic growth at the onset of dehydration, while the orthorhombic type-C CPO for the coarse-grained olivine, especially the [001] point maximum along the lineation, is mainly developed by anisotropic growth resulting from anisotropic fluid flow during the dehydration. The developed olivine type-C CPO in the antigorite-rich layer after antigorite dehydration could explain the trench or strike parallel seismic anisotropy observed at convergent plate boundaries.</p>

Overriding-plate deformation during micro-continent accretion

2020 ◽  
Author(s):  
Zoltán Erdős ◽  
Ritske S. Huismans ◽  
Claudio Faccenna
Keyword(s):  
Plate Boundary ◽  
Slab Thickness ◽  
Plate Boundaries ◽  
Complex Structures ◽  
Model Experiments ◽  
Plate Deformation ◽  
Convergent Plate Boundaries ◽  
The Right ◽  
Back Arc ◽  
Subducting Slab

<p>Both divergent and convergent plate boundaries had been studied extensively throughout the last five decades. Among a host of other aspects came the realization, that given the right circumstances, a broad extensional basin can form behind a convergent plate boundary. The exact mechanisms triggering back-arc extension and why they are episodic, lasting only for tens of millions of years is still debated. The absolute and relative velocities of the plates, the age of the subducting oceanic plate and the inherited rheological properties of the back-arc lithosphere are all thought to be key players, shaping the dynamics of the fore-arc - back-arc systems.</p><p>Here we use 2D mantle scale plane-strain thermo-mechanical model experiments to investigate how the accretion of small continental crustal terrains onto the overriding plate affect the dynamics of the subducting slab and the deformation of the overriding plate.</p><p>Our results suggest that slab-retreat and back-arc extension can be achieved through the combination of slow convergence and micro-continent accretion. Back-arc extension during fast convergence is also possible through the subsequent accretion of more than one micro-continental terrain. Moreover, even the accretion of one such terrain can produce short (1-5 My) episodes of extension-contraction-quiescence in the overriding plate. These episodes are connected to slab break-off events, slab-interaction with upper mantle phase-change boundaries and variations in slab-pull due varying slab thickness.</p><p>Our model experiments also result in complex structures in the overriding plate where discrete outcrops from a single oceanic basin are preserved on the surface hundreds of kilometres apart. This indicates that in nature a simple accretion scenario could produce a surface geological record that is difficult to decipher. Our results compare favourably to observations from the Aegean back-arc basin.</p>

Coastal uplift in continental collision plate boundaries: data from the Last Interglacial marine terraces of the Gibraltar Strait area (south Spain)

1999 ◽  
Vol 301 (1-2) ◽  
pp. 95-109 ◽  
Author(s):  
C Zazo ◽  
P.G Silva ◽  
J.L Goy ◽  
C Hillaire-Marcel ◽  
B Ghaleb ◽  
...  
Keyword(s):  
Continental Collision ◽  
Plate Boundaries ◽  
Last Interglacial ◽  
Marine Terraces ◽  
Gibraltar Strait ◽  
Coastal Uplift
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