Hotter mantle but colder subduction in the Precambrian: What are the implications?

Perchuk, A. L.; Захаров, В. С.; Gerya, Taras; Brown, Michael

doi:10.1016/j.precamres.2019.04.023

Cited by 37 publications

(35 citation statements)

References 53 publications

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“…The prescribed horizontal plate velocity is imposed in the grid nodes located between 100 and 1800 km horizontally and between the oceanic Moho and the 1300 °C isotherm vertically. Our previous study 20 demonstrated that, due to the low asthenosphere viscosity at elevated mantle potential temperature in the Archean, characteristic subduction velocity increases strongly and our prescribed elevated subduction velocities of 10 cm/year are thus plausible. In some models, this prescribed plate velocity condition was deactivated at 20 myrs and the subducting plate is allowed to move freely (Suppl.…”

Section: Methodsmentioning

confidence: 55%

Depletion of the upper mantle by convergent tectonics in the Early Earth

Perchuk

Gerya²,

Захаров

et al. 2021

Sci Rep

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Partial melting of mantle peridotites at spreading ridges is a continuous global process that forms the oceanic crust and refractory, positively buoyant residues (melt-depleted mantle peridotites). In the modern Earth, these rocks enter subduction zones as part of the oceanic lithosphere. However, in the early Earth, the melt-depleted peridotites were 2–3 times more voluminous and their role in controlling subduction regimes and the composition of the upper mantle remains poorly constrained. Here, we investigate styles of lithospheric tectonics, and related dynamics of the depleted mantle, using 2-D geodynamic models of converging oceanic plates over the range of mantle potential temperatures (Tp = 1300–1550 °C, ∆T = T − Tmodern = 0–250 °C) from the Archean to the present. Numerical modeling using prescribed plate convergence rates reveals that oceanic subduction can operate over this whole range of temperatures but changes from a two-sided regime at ∆T = 250 °C to one-sided at lower mantle temperatures. Two-sided subduction creates V-shaped accretionary terrains up to 180 km thick, composed mainly of highly hydrated metabasic rocks of the subducted oceanic crust, decoupled from the mantle. Partial melting of the metabasic rocks and related formation of sodic granitoids (Tonalite–Trondhjemite–Granodiorite suites, TTGs) does not occur until subduction ceases. In contrast, one sided-subduction leads to volcanic arcs with or without back-arc basins. Both subduction regimes produce over-thickened depleted upper mantle that cannot subduct and thus delaminates from the slab and accumulates under the oceanic lithosphere. The higher the mantle temperature, the larger the volume of depleted peridotites stored in the upper mantle. Extrapolation of the modeling results reveals that oceanic plate convergence at ∆T = 200–250 °C might create depleted peridotites (melt extraction of > 20%) constituting more than half of the upper mantle over relatively short geological times (~ 100–200 million years). This contrasts with the modeling results at modern mantle temperatures, where the amount of depleted peridotites in the upper mantle does not increase significantly with time. We therefore suggest that the bulk chemical composition of upper mantle in the Archean was much more depleted than the present mantle, which is consistent with the composition of the most ancient lithospheric mantle preserved in cratonic keels.

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Section: Methodsmentioning

confidence: 55%

Depletion of the upper mantle by convergent tectonics in the Early Earth

Perchuk

Gerya²,

Захаров

et al. 2021

Sci Rep

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show abstract

“…A “hot subduction” geotherm is needed to induce melting within the pressure range suitable for TTG formation (e.g., Moyen & Martin, 2012). While a hotter mantle, as likely prevailed in the Archean, should help induce slab melting, regional scale subduction models have found that slabs sink steeply and quickly into the mantle under such conditions, leading to geotherms that would not induce crustal melting (Perchuk et al, 2019; van Hunen & van den Berg, 2008). In fact, Perchuk et al (2019) finds that subduction is colder at Archean mantle conditions than at present day conditions, due to rapid, steep descent of the slab through the mantle.…”

Section: Discussionmentioning

confidence: 99%

“…While a hotter mantle, as likely prevailed in the Archean, should help induce slab melting, regional scale subduction models have found that slabs sink steeply and quickly into the mantle under such conditions, leading to geotherms that would not induce crustal melting (Perchuk et al, 2019; van Hunen & van den Berg, 2008). In fact, Perchuk et al (2019) finds that subduction is colder at Archean mantle conditions than at present day conditions, due to rapid, steep descent of the slab through the mantle. However, these subduction models impose weak zones in the lithosphere to allow subduction to initiate, rather than allowing the weak zones to form as a result of the rheology and mantle driving forces.…”

Section: Discussionmentioning

confidence: 99%

Timescale of Short‐Term Subduction Episodicity in Convection Models With Grain Damage: Applications to Archean Tectonics

Foley

2020

JGR Solid Earth

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The style of subduction that prevailed on the early Earth, or even whether subduction was prevalent at all, is an important question in the evolution of Earth's crust, mantle, and surface environment. Here, two-dimensional numerical convection models, that include grain size evolution to generate weak plate boundaries, reveal a clear transition in subduction behavior with increasing internal heating rate. Sustained subduction with a coherent slab gives way to a style where slabs periodically detach and sink rapidly into the deep mantle, with increasing internal heating rate. In this latter, "drip-like" subduction regime, repeating cycles of slab growth by subduction, followed by necking and detachment of the lower portion of the slab, are seen. These cycles are termed "slab detachment cycles," and similar behavior has been seen in regional scale subduction models of the early Earth. Fourier analysis is used to constrain the timescale of slab detachment cycles, and a simple scaling law for this timescale is developed. Applying the scaling law to the early Earth indicates that slab detachment cycles can occur on timescales of <10 Myr, even as low as <5 Myr if the lithosphere is thick and mantle temperature is >1900 K. These cycles may thus be capable of explaining repeating sequences of rocks with "arc" and "non-arc" signatures seen in some Archean cratons. The drip-like subduction regime could also have significant implications for the generation of the tonalite-trondhjemite-granodiorite (TTG) suite of rocks and exhumation of high pressure metamorphic rocks, two important features of the early Earth geologic record.

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“…Delamination of the mantle lithosphere in long-lived ultra-hot accretionary orogens controlled silicification and rising of the continents due to recycling of mafic lower crust (Perchuk et al, 2018;Chowdhury et al, 2017). The episodic (short-lived), rapidly retreating subduction was associated with massive decompression melting of the mantle resulting in formation of oceanic plateau basalts (Perchuk et al, 2019). • The establishment of modern-style plate tectonics at ca.…”

Section: Geodynamics Of the Early Earth: Quest For The Missing Paradigmmentioning

confidence: 99%

Geodynamics of the early Earth: Quest for the missing paradigm

Gerya

2019

Geology

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Hotter mantle but colder subduction in the Precambrian: What are the implications?

Cited by 37 publications

References 53 publications

Depletion of the upper mantle by convergent tectonics in the Early Earth

Depletion of the upper mantle by convergent tectonics in the Early Earth

Timescale of Short‐Term Subduction Episodicity in Convection Models With Grain Damage: Applications to Archean Tectonics

Geodynamics of the early Earth: Quest for the missing paradigm

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