Dynamics of subduction initiation at preexisting fault zones

Toth, John R.; Gurnis, Michael

doi:10.1029/98jb01076

Cited by 237 publications

(254 citation statements)

References 36 publications

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“…The drawback of using a fault is the presence of a stress discontinuity at either end of the fault. The stress singularity in the mantle can be avoided by tapering the degree of coupling along the fault [Toth and Gurnis, 1998;van Hunen et al, 2000], but the discontinuity at the surface leads to inaccurate topography. In lowresolution models, using a discrete fault is preferable to a broad low-viscosity region, which is not capable of fully decoupling the two plates [Zhong et al, 1998].…”

Section: Plate Boundary Shear Zonementioning

confidence: 99%

Rheologic controls on slab dynamics

Billen

Hirth

2007

Geochem Geophys Geosyst

205

186

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[1] Several models have been proposed to relate slab geometry to parameters such as plate velocity or plate age. However, studies on the observed relationships between slab geometry and a wide range of subduction parameters show that there is not a simple global relationship between slab geometry and any one of these other subduction parameters for all subduction zones. Numerical and laboratory models of subduction provide a method to explore the relative importance of different physical processes in determining subduction dynamics. Employing 2-D numerical models with a viscosity structure constrained by laboratory experiments for the deformation of olivine, we show that the observed range in slab dip and the observed trends between slab dip and convergence velocity, subducting plate age, and subduction duration can be reproduced without trench motion (i.e., slab roll-back) for locations away from slab edges. Successful models include a stiff slab that is 100-1000 times more viscous than previous estimates from models of plate bending, the geoid, and global plate motions. We find that slab dip in the upper mantle depends primarily on slab strength and plate boundary coupling, with a small dependence on subducting plate age. Once the slab sinks into the lower mantle the primary processes controlling slab evolution are (1) the ability of the stiff slab to transmit stresses up dip, (2) resistance to slab descent into the higherviscosity lower mantle, and (3) subduction-induced flow in the mantle-wedge corner.

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Section: Plate Boundary Shear Zonementioning

confidence: 99%

Rheologic controls on slab dynamics

Billen

Hirth

2007

Geochem Geophys Geosyst

205

186

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“…Subduction initiation has been addressed primarily through numerical modeling (2)(3)(4)(5)(6)(7)(8)(9). These studies have demonstrated the need for a weak zone in the lithosphere to facilitate subduction.…”

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confidence: 99%

“…In "spontaneous" subduction initiation, a plate's increasing density with age may eventually cause it to sink into the underlying asthenosphere (10,14), whereas in forced subduction initiation, external plate forces are required to initiate subduction (3,5,15). Oceanic plates that are at least ∼10 My old are negatively buoyant (16) and may undergo either forced or spontaneous subduction initiation.…”

mentioning

confidence: 99%

Rapid conversion of an oceanic spreading center to a subduction zone inferred from high-precision geochronology

Keenan

Encarnación

Buchwaldt

et al. 2016

Proc. Natl. Acad. Sci. U.S.A.

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Where and how subduction zones initiate is a fundamental tectonic problem, yet there are few well-constrained geologic tests that address the tectonic settings and dynamics of the process. Numerical modeling has shown that oceanic spreading centers are some of the weakest parts of the plate tectonic system [Gurnis M, Hall C, Lavier L (2004) Geochem Geophys Geosys 5:Q07001], but previous studies have not favored them for subduction initiation because of the positive buoyancy of young lithosphere. Instead, other weak zones, such as fracture zones, have been invoked. Because these models differ in terms of the ages of crust that are juxtaposed at the site of subduction initiation, they can be tested by dating the protoliths of metamorphosed oceanic crust that is formed by underthrusting at the beginning of subduction and comparing that age with the age of the overlying lithosphere and the timing of subduction initiation itself. In the western Philippines, we find that oceanic crust was less than ∼1 My old when it was underthrust and metamorphosed at the onset of subduction in Palawan, Philippines, implying forced subduction initiation at a spreading center. This result shows that young and positively buoyant, but weak, lithosphere was the preferred site for subduction nucleation despite the proximity of other potential weak zones with older, denser lithosphere and that plate motion rapidly changed from divergence to convergence. subduction initiation | tectonics | geochronology | Philippines | ophiolite

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“…[69] Several studies have shown that subduction zones may preferentially initiate along preexisting oceanic fracture zones [e.g., Casey and Dewey, 1984;Scholl et al, 1998;Lebrun et al, 1998;Toth and Gurnis, 1998]. We should thus expect fracture zones that parallel the main suture to be common in ancient zones of ocean-ocean or ocean-continent convergence.…”

Section: Discussionmentioning

confidence: 99%

Early Proterozoic oceanic crust in the northern Colorado Front Range: Implications for crustal growth and initiation of basement faults

Cavosie¹,

Selverstone

2003

Tectonics

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Early Proterozoic oceanic crust exposed in a shear zone in the northern Colorado Front Range provides insight into the tectonic evolution of the Colorado province. Tectonically intermingled mylonitic amphibolite (locally pillowed), metagabbro, clinopyroxenite, metachert, and mélange are preserved within the Buckhorn Creek shear zone west of Fort Collins. Whole rock geochemical data support formation of the igneous protoliths in an oceanic environment. Major and trace element data overlap samples from modern oceanic ridges, and are distinct from modern arc trends. Metagabbros and clinopyroxenites preserve a subhorizontal lineation defined by igneous pyroxenes; core and mantle microstructures indicate initial deformation at temperatures >900°C. Secondary amphiboles define both subhorizontal and subvertical lineations. Kinematic analysis indicates that the rocks experienced E‐W strike‐slip deformation prior to and during amphibolite‐facies metamorphism, followed by N‐S shortening. 40Ar/39Ar data from secondary hornblende yield age steps as old as 1.9 Ga. Based on the chemical data and kinematic evidence for strike‐slip deformation, we propose that the Buckhorn Creek rocks originated at an oceanic ridge‐transform intersection. The high‐T pyroxene fabrics formed during ocean floor deformation prior to 1.7 Ga regional deformation of the Colorado province. The Buckhorn Creek fragment likely represents original oceanic basement for 1.8–1.7 Ga arc magmatism and sedimentation that ultimately formed the Colorado province continental crust. Reactivation of original oceanic fracture zones may be responsible for the network of regularly spaced northeast trending shear zones in Colorado. Once formed, subvertical transform faults are likely to survive the transition from oceanic to continental crust and persist as long‐lived crustal discontinuities.

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Dynamics of subduction initiation at preexisting fault zones

Cited by 237 publications

References 36 publications

Rheologic controls on slab dynamics

Rheologic controls on slab dynamics

Rapid conversion of an oceanic spreading center to a subduction zone inferred from high-precision geochronology

Early Proterozoic oceanic crust in the northern Colorado Front Range: Implications for crustal growth and initiation of basement faults

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