Rheology of the Upper Mantle: A Synthesis

Karato, Shun‐ichiro; Wu, Patrick

doi:10.1126/science.260.5109.771

Cited by 1,564 publications

(1,381 citation statements)

References 70 publications

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“…Similar plots, in this case versus depth, for a range of flow laws for wet to dry olivine ( Figure A1b) show that the range of laboratory flow laws can be reproduced with reasonable accuracy by the Karato and Wu [1993] flow law with an activation volume, V* = 10 cm 3 /mol and f = 1-10. We therefore use the WOL flow law with scaled values in this range to represent power law creep in olivine controlled rocks that vary from wet (water saturated) to dry.…”

Section: A4 Choice Of Laboratory Flow Laws and Rationale For F Scalingsupporting

confidence: 55%

“…Upper/middle continental crusts have a scaled wet quartzite flow law (WQ × f, where f varies among crustal units) [Gleason and Tullis, 1995], whereas lower continental and oceanic crusts have a scaled dry Maryland diabase flow law (DMD × 0.05 and 0.1, respectively) [Mackwell et al, 1998]. Mantle materials have a wet olivine flow law (WOL) [Karato and Wu, 1993] scaled to represent either sublithospheric mantle or dehydrated lithospheric mantle.…”

Section: Journal Of Geophysicalmentioning

confidence: 99%

“…The rift basin comprises an upper 4 km of sediment overlying 4 km of lower crust, while the oceanic plate comprises 6 km of oceanic crust (ϕ = 15-4°; DMD × 0.1) overlain by 2 km of sediment. The underlying lithospheric mantle extends to 120 km beneath the continents and to 90 km beneath the oceanic plate has ϕ = 15-4°and a wet olivine flow law (WOL × 10) [Karato and Wu, 1993] scaled to represent a somewhat depleted/dehydrated lithosphere and overlies sublithospheric mantle (WOL × 1) that extends to 660 km.…”

Section: /2013jb010799mentioning

confidence: 99%

“…We choose to base the power law flow calculations in the models on a reference set of well constrained laboratory experimental [Gleason and Tullis, 1995]; melt absent Black Hills quartzite), dry diabase (DMD [Mackwell et al, 1998]; dry Maryland diabase), and wet olivine (WOL) [Karato and Wu, 1993]. Laboratory-derived flow laws are subject to significant uncertainties associated with the measurements on individual samples, the variability of measured results among samples of similar rock types, the range of deformation mechanisms, the effects of water fugacity, the variability of results among different laboratories, and the known and unknown errors in extrapolating the laboratory results to natural conditions.…”

Section: A4 Choice Of Laboratory Flow Laws and Rationale For F Scalingmentioning

confidence: 99%

“…(b) Log effective viscosity versus depth for model mantle flow laws, calculated for a strain rate of 10 À16 /s, and assuming a mantle density of 3200 kg/m 3 and adiabatic temperature gradient of 0.3 K/km. WOL = wet olivine [Karato and Wu, 1993, KW93]; DOL = dry olivine [Karato and Wu, 1993]. Blue lines show wet olivine flow law of Hirth et al [2001, HO1] for water concentrations of 200, 800, and 3000 ppm.…”

Section: A4 Choice Of Laboratory Flow Laws and Rationale For F Scalingmentioning

confidence: 99%

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The Alps 2: Controls on crustal subduction and (ultra)high‐pressure rock exhumation in Alpine‐type orogens

2014

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Building on our previous results, we use 2-D upper mantle-scale thermomechanical numerical models to explore key controls on the evolution of Alpine-type orogens and the Alps per se, focusing on (ultra)high-pressure ((U)HP) metamorphic rocks. The models show that UHP rocks form and exhume by burial and subsequent buoyant ascent of continental crust in the subduction conduit. Here we test the sensitivity of the models to surface erosion rate, crustal heat production, plate convergence/divergence rates, geometry of the subducting continental margin, and strength of the retrocontinent. Surface erosion affects crustal exhumation but not early buoyant exhumation. Metamorphic temperatures increase with crustal radioactive heat production. Maximum burial depth prior to exhumation increases with plate convergence rates, but exhumation rates are only weakly dependent on subduction rates. Onset of absolute plate divergence does not trigger exhumation in these models. We conclude that contrasting peak pressures, exhumation rates, and volumes of (U)HP crust exhumed in the Alps orogen primarily reflect along-strike contrasts in the geometry, thermal structure, and/or strength of the subducting microcontinent (Briançonnais) and continental (European margin) crust. The experiments also support the interpretation that the Western Alps (U)HP Internal Crystalline Massifs exhumed as composite, stacked plumes and that these plumes drove local crustal extension during orogen-scale shortening. For weak upper plate retrocrusts, postexhumation retrothrusting forms a retrowedge. Overall, these results are consistent with predictions using the exhumation number (ratio of buoyancy to side traction forces in the conduit), which expresses the combined parameter control of the depth/volume of crustal subduction and the transition to buoyant exhumation.

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Section: A4 Choice Of Laboratory Flow Laws and Rationale For F Scalingsupporting

confidence: 55%

Section: Journal Of Geophysicalmentioning

confidence: 99%

Section: /2013jb010799mentioning

confidence: 99%

Section: A4 Choice Of Laboratory Flow Laws and Rationale For F Scalingmentioning

confidence: 99%

Section: A4 Choice Of Laboratory Flow Laws and Rationale For F Scalingmentioning

confidence: 99%

See 3 more Smart Citations

The Alps 2: Controls on crustal subduction and (ultra)high‐pressure rock exhumation in Alpine‐type orogens

2014

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A systematic 2‐D investigation into the mantle wedge's transient flow regime and thermal structure: Complexities arising from a hydrated rheology and thermal buoyancy

Voci

Davies

Goes

et al. 2014

Geochem Geophys Geosyst

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[1] Arc volcanism at subduction zones is likely regulated by the mantle wedge's flow regime and thermal structure and, hence, numerous studies have attempted to quantify the principal controls on mantle wedge conditions. In this paper, we build on these previous studies by undertaking a systematic 2-D numerical investigation into how a hydrated rheology and thermal buoyancy influence the wedge's flow regime and associated thermal structure. We quantify the role of a range of plausible: (i) water contents (0-5000 H/10 6 Si); (ii) subduction velocities (2-10 cm/yr); and (iii) upper-plate ages (50-120 Myr), finding that small-scale convection (SSC), resulting from Rayleigh-Taylor instabilities, or drips, off the base of the overriding lithosphere, is a typical occurrence. The morphology of SSC varies with viscosity and subduction parameters, with drips at their most prominent when subduction velocities and wedge viscosities are low. Our results confirm that high subduction velocities and wedge viscosities promote a dominantly corner-flow regime, and strong upper-plate erosion below the arc region. By contrast, we find that back-arc upper-plate erosion by SSC is largely controlled by wedge viscosity, occurring when: (i) viscosities are < 5Á10 18 Pa s; and (ii) the length of the upper plate, available for destabilization, exceeds the characteristic wavelength of instabilities. Thus, if hydrous weakening of wedge rheology extends at least 100-150 km from the trench, our 2-D models predict an unstable flow regime, resulting in temperature fluctuations of 50-100 K, which are sufficient to influence melting and the stability of hydrous minerals.

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Buildup of a dynamically supported orogenic plateau: Numerical modeling of the Zagros/Central Iran case study

François

Burov

Agard

et al. 2014

Geochem Geophys Geosyst

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The Iranian plateau is a vast inland region with a smooth average elevation of c. 1.5 km formed at the rear of the Zagros orogen as a result of the Arabia-Eurasia collision (i.e., over the last [30][31][32][33][34][35]. This collision zone is of particular interest due to its disputed resemblance to the faster Himalayan collision, which gave birth to the Tibetan plateau around 50 Myr ago. Recent studies have suggested that a recent (10-5 Ma) slab break-off event below Central Iran caused the formation of the Iranian plateau. Here, we test several hypotheses through large-scale (3082 3 590 km) numerical models of continental subduction models that incorporate a free upper surface erosion, rheological stratification, brittle-elastic-ductile rheologies, and metamorphic phase changes (density and physical properties) and account for the specific crustal and thermal structure of the Arabian and Iranian continental lithospheres. We test the impact of the transition from oceanic to continental subduction and the topographic consequences of the progressive slowdown of the convergence rate during continental subduction. Our results demonstrate the role of mantle flow beneath the overriding plate, initiated as an indirect consequence of slab break-off. This flow creates a dynamic topography support during continental subduction and results in delamination of the overriding plate lithospheric mantle followed by isostatic readjustment, hence of further uplift and maintenance of a plateau-like topography without significant crustal thickening. The slowdown of the convergence rate during the development of the continental subduction/collision phase largely contributes to this process by controlling the timing and depth of slab break-off.

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Rheology of the Upper Mantle: A Synthesis

Cited by 1,564 publications

References 70 publications

The Alps 2: Controls on crustal subduction and (ultra)high‐pressure rock exhumation in Alpine‐type orogens

The Alps 2: Controls on crustal subduction and (ultra)high‐pressure rock exhumation in Alpine‐type orogens

A systematic 2‐D investigation into the mantle wedge's transient flow regime and thermal structure: Complexities arising from a hydrated rheology and thermal buoyancy

Buildup of a dynamically supported orogenic plateau: Numerical modeling of the Zagros/Central Iran case study

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