Continental crustal volume, thickness and area, and their geodynamic implications

Cawood, Peter A.; Hawkesworth, Chris J.

doi:10.1016/j.gr.2018.11.001

Cited by 77 publications

(40 citation statements)

References 100 publications

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“…The action of life increases the amounts of weathering and hence the amounts of water returned to the mantle in sediments. Water in the mantle helps serve as a lubricant, facilitating convection and plate movement, and perhaps constraining the fraction of the surface covered by emergent continents (Honing et al, 2014;Cawood and Hawkesworth, 2019). Most life is found on continents and continental shelves.…”

Section: Wider Implicationsmentioning

confidence: 99%

“…If the crust was relatively weak in the Archean then there may have been relatively little in the way of mountain building, and even significant topographic relief, in continental areas before the late Archean (Cawood and Hawkesworth, 2019). Most Archean sedimentary rocks are preserved in greenstone belts, and they were deposited in shallow water, often in coastal plain type environments (Eriksson et al, 1994).…”

Section: Geological Evidence Relative Strength Of the Crustmentioning

confidence: 99%

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The Evolution of the Continental Crust and the Onset of Plate Tectonics

2020

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The Earth is the only known planet where plate tectonics is active, and different studies have concluded that plate tectonics commenced at times from the early Hadean to 700 Ma. Many arguments rely on proxies established on recent examples, such as paired metamorphic belts and magma geochemistry, and it can be difficult to establish the significance of such proxies in a hotter, older Earth. There is the question of scale, and how the results of different case studies are put in a wider global context. We explore approaches that indicate when plate tectonics became the dominant global regime, in part by evaluating when the effects of plate tectonics were established globally, rather than the first sign of its existence regionally. The geological record reflects when the continental crust became rigid enough to facilitate plate tectonics, through the onset of dyke swarms and large sedimentary basins, from relatively highpressure metamorphism and evidence for crustal thickening. Paired metamorphic belts are a feature of destructive plate margins over the last 700 Myr, but it is difficult to establish whether metamorphic events are associated spatially as well as temporally in older terrains. From 3.8 to 2.7 Ga, suites of high Th/Nb (subduction-related on the modern Earth) and low Th/Nb (non-subduction-related) magmas were generated at similar times in different locations, and there is a striking link between the geochemistry and the regional tectonic style. Archean cratons stabilized at different times in different areas from 3.1 to 2.5 Ga, and the composition of juvenile continental crust changed from mafic to more intermediate compositions. Xenon isotope data indicate that there was little recycling of volatiles before 3 Ga. Evidence for the juxtaposition of continental fragments back to ∼2.8 Ga, each with disparate histories highlights that fragments of crust were moving around laterally on the Earth. The reduction in crustal growth at ∼3 Ga is attributed to an increase in the rates at which differentiated continental crust was destroyed, and that coupled with the other changes at the end of the Archean are taken to reflect the onset of plate tectonics as the dominant global regime.

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Section: Wider Implicationsmentioning

confidence: 99%

Section: Geological Evidence Relative Strength Of the Crustmentioning

confidence: 99%

The Evolution of the Continental Crust and the Onset of Plate Tectonics

2020

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“…Melting at depths >35-45 km requires either an exceptionally thick primary crust, or the presence of some convergent tectonics that can bury the mafic crust to those depths. Although cannot be ruled out, a widespread presence of >35-40 km thick mafic crust lacks strong geological support 48,49 . On the contrary, isolated events of hotter subduction 6,7,29,50 and lithospheric peeling driven convergent tectonics 29,31,32 have been invoked to occur under the Archaean mantle conditions.…”

Section: Discussionmentioning

confidence: 99%

Archaean Cratons Record a Duality of Melting Regimes During Early Continental Growth

Ladwig¹,

Chowdhury²,

McCoy-West³

et al. 2020

Preprint

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The tectonic setting and pressure-temperature conditions responsible for the formation of felsic crust on the early Earth remain debated. Rare earth elements (REE) have been extensively used to study the formation of tonalite-trondhjemites-granodiorites (TTGs)- the building blocks of the early felsic crust, but conclusive interpretations based on the chondrite-normalized REE patterns have not materialised because of the inability to distinguish subtle differences. Here we apply a polynomial approach that quantifies the REE patterns by describing their slope and curvature using shaping coefficients to the TTG compositions from five different Archaean cratons. In combination with partial melting modelling, this enables an assessment of the effects of variations in pressure-temperature, degree of melting and residual mineral assemblages on the formation of TTGs. The REE composition of the Archaean TTGs display two distinct trends: (1) a horizontal-trend suggesting their formation in the presence of garnet-poor amphibolitic residues, possibly formed at the base of a thickened crust; and, (2) an inclined-trend consistent with their formation in equilibration with amphibole-poor, but garnet-rich residues at convergent settings (but not necessarily related to plate tectonics). These different melting regimes coexisted during the Paleoarchaean to Neoarchaean and provide direct evidence for a duality of petro-tectonic regimes of felsic crust formation on the early Earth.

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“…10 to 120% of its present-day volume between the different growth models (Figure 3) (cf. Cawood and Hawkesworth, 2019). This is because these models are based on different assumptions and datasets.…”

Section: Comparison With the Volume Of ∼3 Ga Old Continental Crustmentioning

confidence: 99%

Calibrating the Yield Strength of Archean Lithosphere Based on the Volume of Tonalite-Trondhjemite-Granodiorite Crust

Gunawardana¹,

Morra

Chowdhury³

et al. 2020

Front. Earth Sci.

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Lithospheric yield stress is a key parameter in controlling tectonic processes. Using high resolution, 2D numerical modeling, we calculate the yield stress for a range of conditions appropriate to the early-to-mid Archean Earth, including hotter mantle potential temperatures and Moho temperatures. We then evaluate its effect on generating tonalite-trondhjemite-granodiorite (TTG) crust and benchmark the results against the preserved igneous rock record. Our results indicate that lithospheric yield stress values lower than the present-day values (i.e., ≤100 MPa) can generate TTG volumes similar to those preserved in the rock record. The models further highlight the dominance of lithospheric dripping in producing the Archean TTGs. Large volumes of TTG melts form within the thin, tail portions of the drips as these regions are more efficiently heated by the enclosing hotter mantle. In contrast, only limited melting occurs within the thickened parts of lithosphere as they are significantly weak and cannot sustain crustal thickening for long time periods, resulting in its removal via dripping. This study, therefore, reaffirms the dominance of non-plate tectonic mechanisms in producing TTGs under the conditions that operated on the hotter Archean Earth.

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Continental crustal volume, thickness and area, and their geodynamic implications

Cited by 77 publications

References 100 publications

The Evolution of the Continental Crust and the Onset of Plate Tectonics

The Evolution of the Continental Crust and the Onset of Plate Tectonics

Archaean Cratons Record a Duality of Melting Regimes During Early Continental Growth

Calibrating the Yield Strength of Archean Lithosphere Based on the Volume of Tonalite-Trondhjemite-Granodiorite Crust

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