THE EVOLUTION OF CONTINENTAL COLLISION CONTROLLED BY THE WIDTH OF ADJACENT SUBDUCTION ZONE

Abstract. Continental collision is an intrinsic feature of plate tectonics. The closure of an oceanic basin leads to the onset of subduction of buoyant continental material, which slows down and eventually stops the subduction process. In natural cases, evidence of advancing margins has been recognized in continental collision zones such as India-Eurasia and Arabia-Eurasia. We perform a parametric study of the geometrical and rheological influence on subduction dynamics during the subduction of continental lithosphere. In our 2-D numerical models of a free subduction system with temperature and stress-dependent rheology, the trench and the overriding plate move self-consistently as a function of the dynamics of the system (i.e. no external forces are imposed). This setup enables to study how continental subduction influences the trench migration. We found that in all models the slab starts to advance once the continent enters the subduction zone and continues to migrate until few million years after the ultimate slab detachment. Our results support the idea that the advancing mode is favoured and, in part, provided by the intrinsic force balance of continental collision. We suggest that the advance is first induced by the locking of the subduction zone and the subsequent steepening of the slab, and next by the sinking of the deepest oceanic part of the slab, during stretching and break-off of the slab. These processes are responsible for the migration of the subduction zone by triggering small-scale convection cells in the mantle that, in turn, drag the plates. The amount of advance ranges from 40 to 220 km and depends on the dip angle of the slab before the onset of collision.

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The February 28, 2006 Tiab earthquake, Mw 6.0: Implications for tectonics of the transition between the Zagros continental collision and the Makran subduction zone

Journal of Geodynamics ◽

10.1016/j.jog.2009.01.005 ◽

2009 ◽

Vol 47 (5) ◽

pp. 280-287 ◽

Cited By ~ 12

Author(s):

A. Gholamzadeh ◽

F. Yamini-Fard ◽

K. Hessami ◽

M. Tatar

Keyword(s):

Subduction Zone ◽

Continental Collision ◽

Makran Subduction Zone

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Numerical models of trench migration in continental collision zones

Solid Earth Discussions ◽

10.5194/sed-4-429-2012 ◽

2012 ◽

Vol 4 (1) ◽

pp. 429-458 ◽

Cited By ~ 2

Author(s):

V. Magni ◽

J. van Hunen ◽

F. Funiciello ◽

C. Faccenna

Keyword(s):

Subduction Zone ◽

Plate Tectonics ◽

Numerical Models ◽

Continental Collision ◽

Force Balance ◽

Dip Angle ◽

External Forces ◽

Stress Dependent ◽

Subduction System ◽

Intrinsic Feature

Abstract. Continental collision is an intrinsic feature of plate tectonics. The closure of an oceanic basin leads to the onset of subduction of buoyant continental material, which slows down and eventually stops the subduction process. We perform a parametric study of the geometrical and rheological influence on subduction dynamics during the subduction of continental lithosphere. In 2-D numerical models of a free subduction system with temperature and stress-dependent rheology, the trench and the overriding plate move self-consistently as a function of the dynamics of the system (i.e. no external forces are imposed). This setup enables to study how continental subduction influences the trench migration. We found that in all models the trench starts to advance once the continent enters the subduction zone and continues to migrate until few million years after the ultimate slab detachment. Our results support the idea that the trench advancing is favoured and, in part provided by, the intrinsic force balance of continental collision. We suggest that the trench advance is first induced by the locking of the subduction zone and the subsequent steepening of the slab, and next by the sinking of the deepest oceanic part of the slab, during stretching and break-off of the slab. The amount of trench advancing ranges from 40 to 220 km and depends on the dip angle of the slab before the onset of collision.

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Syn-exhumation magmatism in an active continental margin above a continental subduction zone: Evidence from Late Triassic mafic igneous rocks in the southeastern North China Block

Geological Society of America Bulletin ◽

10.1130/b35656.1 ◽

2020 ◽

Author(s):

Wei Fang ◽

Li-Qun Dai ◽

Yong-Fei Zheng ◽

Zi-Fu Zhao ◽

Qi Chen ◽

...

Keyword(s):

Subduction Zone ◽

Continental Margin ◽

North China ◽

Mantle Wedge ◽

Active Continental Margin ◽

Continental Collision ◽

Igneous Rocks ◽

Late Triassic ◽

North China Block ◽

Continental Subduction

Syn-subduction arc magmatism is absent above continental subduction zones, providing important constraints on the nature of petrogenetic processes during continental collision. Nevertheless, we have identified syn-exhumation mafic igneous rocks in an active continental margin above a continental subduction zone, where the South China Block (SCB) was deeply subducted beneath the North China Block (NCB) for collisional orogeny in the Triassic. These mafic igneous rocks occur in the southeastern margin of the NCB, showing consistent Late Triassic zircon U-Pb ages of ca. 219−218 Ma, coeval with exhumation of the deeply subducted continental crust. These rocks are categorized into two series of sub-alkaline and alkaline, all exhibiting arc-like trace element distribution patterns, highly enriched radiogenic Sr-Nd-Hf and high zircon O isotope compositions. In particular, they exhibit two-stage whole-rock Nd and Hf model ages and zircon Hf model ages of Paleoproterozoic, which are comparable to those of ultrahigh-pressure metamorphic rocks with the SCB affinity in the Dabie-Sulu orogenic belt. Such geochemical features indicate that these mafic igneous rocks were derived from partial melting of ultramafic metasomatites generated by reaction of felsic melts from the subducted SCB with the mantle wedge peridotite beneath the NCB. The geochemical differences in element and isotope compositions between the two series igneous rocks can be mainly ascribed to different proportions of the crustal component in the metasomatites, which is verified by quantitative modellings of the geochemical transfer in the continental subduction zone. The systematic variations in some geochemical variables such as Fe/Mn, Zn/Fe, and Nb/Ta ratios indicate pyroxenite-rich and hornblendite-rich lithologies, respectively, for the sub-alkaline and alkaline series igneous rocks. With the tectonic extension for exhumation of the deeply subducted continental crust in the Late Triassic, the fertile and enriched metasomatites in the mantle wedge underwent partial melting for the syn-exhumation mafic magmatism in the southeastern NCB. Therefore, the mafic igneous rocks in the active continental margin not only record the crust-mantle interaction in the continental subduction zone, but also witness the generation of syn-exhumation magmatism in the late stage of continental collision.

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