Lower crustal flow kept Archean continental flood basalts at sea level

Flament, Nicolas; Rey, Patrice; Coltice, Nicolas; Dromart, G.; Olivier, Nicolas

doi:10.1130/g32231.1

Cited by 34 publications

(13 citation statements)

References 26 publications

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“…These observations are similar to those made by Nair et al [] and Kgaswane et al [] in Africa and Yuan [] in western Australia, suggesting similar processes operating worldwide for Archean continental crust formation [e.g., Abbott et al , ]. Elevated lower crustal temperatures of >650°C at the Moho [e.g., Flament et al , ] in the Archean may have facilitated lower crustal flow, which would prevent significant crustal thickening and lead to relatively uniform Moho depths [e.g., Rey and Houseman , ]. Alternatively, the sharp, flat Moho observed in the Archean domains of northern Hudson Bay was explained by Thompson et al [] as the result of the removal of restite following the formation of Archean TTG (Tonalite‐Trondhjemite‐Granodiorite) suites.…”

Section: Discussionsupporting

confidence: 85%

A tale of two orogens: Crustal processes in the Proterozoic Trans‐Hudson and Grenville Orogens, eastern Canada

et al. 2017

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The Precambrian core of North America was assembled in the Proterozoic by a series of collisions between Archean cratons. Among the orogenic belts, two stand out due to their significant spatial extent. The Paleoproterozoic Trans‐Hudson Orogen (THO) and Mesoproterozoic Grenville Orogen extend for thousands of kilometers along strike and hundreds of kilometers across strike. Both have been compared to the present‐day Himalayan‐Karakoram‐Tibetan Orogen (HKTO). Over the last 20–30 years, active and passive source seismic studies have contributed a wealth of information about the present‐day crustal structure and composition of the two orogens in Canada. The Proterozoic orogenic crust is generally thicker than that of neighboring Archean terranes, with a more variable Moho character, ranging from relatively sharp to highly diffuse. Both orogens have a prominent high‐velocity lower crustal layer, consistent with long‐term preservation of a partially eclogitized root at the base of the crust and similar to that inferred beneath the western HKTO. Crustal structure in the northern THO strongly resembles the lower crustal structure of the HKTO, suggesting that Moho depths may have reached 60–70 km when the orogen was active. A prominent midcrustal discontinuity beneath the central Grenville Province and changes in the patterns of seismic anisotropy in the THO crust beneath Hudson Bay provide geophysical evidence that lower crustal flow likely played a role in the evolution of both orogens, similar to that inferred beneath the present‐day HKTO. The seismic evidence from Canada supports the notion of tectonic uniformitarianism, at least as far back as the Paleoproterozoic.

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Section: Discussionsupporting

confidence: 85%

A tale of two orogens: Crustal processes in the Proterozoic Trans‐Hudson and Grenville Orogens, eastern Canada

et al. 2017

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“…The associated sedimentary rocks are mostly cherts and ironstones (Goodwin, 1991), and clastic sedimentary rocks only appear widely in the geological record after 3.2 Ga (Eriksson and Wilde, 2010). This is consistent with modeling that indicates the continents were mostly flooded until the Neoarchean (Flament et al, 2008(Flament et al, , 2011.…”

Section: The Evolution Of the Continental Lithospheresupporting

confidence: 80%

The contribution of metamorphic petrology to understanding lithosphere evolution and geodynamics

Brown

2014

Geoscience Frontiers

245

138

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a b s t r a c tIn the early 1980s, evidence that crustal rocks had reached temperatures >1000 C at normal lower crustal pressures while others had followed low thermal gradients to record pressures characteristic of mantle conditions began to appear in the literature, and the importance of melting in the tectonic evolution of orogens and metamorphicemetasomatic reworking of the lithospheric mantle was realized. In parallel, new developments in instrumentation, the expansion of in situ analysis of geological materials and increases in computing power opened up new fields of investigation. The robust quantification of pressure (P), temperature (T) and time (t) that followed these advances has provided reliable data to benchmark geodynamic models and to investigate secular change in the thermal state of the lithosphere as registered by metamorphism through time. As a result, the last 30 years have seen significant progress in our understanding of lithospheric evolution, particularly as it relates to Precambrian geodynamics.EoarcheaneMesoarchean crust registers uniformly high T/P metamorphism that may reflect a stagnant lid regime. In contrast, two contrasting types of metamorphism, eclogiteehigh-pressure granulite metamorphism, with apparent thermal gradients of 350e750 C/GPa, and granulite eultrahigh temperature metamorphism, with apparent thermal gradients of 750e1500 C/GPa, appeared in the Neoarchean rock record. The emergence of paired metamorphism is interpreted to register the onset of one-sided subduction, which introduced an asymmetric thermal structure at these developing convergent plate margins characterized by lower T/P in the subduction channel and higher T/P in the overriding plate. During the Paleoarchean to Paleoproterozoic the ambient mantle temperature was warmer than at present by w300e150 C. Although the thermal history of Earth is only poorly constrained, it is likely that prior to c. 3.0 Ga heating from radioactive decay would have exceeded surface heat loss, whereas since c. 2.5 Ga secular cooling has dominated the thermal history of the Earth. The advent of paired metamorphism is consistent with other changes in the geological record during the Neoarchean that are best explained as the result of a transition from a stagnant lid to subduction and a global plate tectonics regime by c. 2.5 Ga. This interpretation is supported by results from 2-D numerical experiments of oceanic subduction that demonstrate a change to one-sided subduction is plausible as upper mantle temperature declined to <200 C warmer than at present during the late NeoarcheanePaleoproterozoic. This is the beginning of the Proterozoic plate tectonics regime.At 1.0 Ga the ambient mantle temperature was still w150e100 C warmer than at present. Continued secular cooling caused a transition to cold subduction registered in the crustal record of metamorphism by the first appearance of blueschist and high to ultrahigh pressure metamorphism during the Neoproterozoic. Results of 2-d numerical experiments of continental collision demon...

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“…Elevated lower‐crustal temperatures (>650°C at the Moho; e.g., Flament et al . []) in the Archean may have facilitated lower‐crustal flow, leading to relatively uniform Moho depths, and prevented crustal thickening [e.g., Rey and Houseman , ]. Alternatively, Thompson et al .…”

Section: Discussionmentioning

confidence: 99%

“…Elevated lower-crustal temperatures (>6508C at the Moho; e.g., Flament et al [2011]) in the Archean may have facilitated lower-crustal flow, leading to relatively uniform Moho depths, and prevented crustal thickening [e.g., Rey and Houseman, 2006]. Alternatively, Thompson et al [2010] explained their H-j stacking-derived observations of a Geochemistry, Geophysics, Geosystems 10.1002/2016GC006419 sharp, flat Moho in the same region through the removal of restite by lower-crustal delamination following the formation of Tonalite-Trondhjemite-Granodiorite suites during the Archean.…”

Section: Archean Domainsmentioning

confidence: 99%

Seismological structure of the 1.8 Ga Trans‐Hudson Orogen of North America

Gilligan

Bastow

Darbyshire

2016

Geochem Geophys Geosyst

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Precambrian tectonic processes are debated: what was the nature and scale of orogenic events on the younger, hotter, and more ductile Earth? Northern Hudson Bay records the Paleoproterozoic collision between the Western Churchill and Superior plates-the 1.8 Ga Trans-Hudson Orogeny (THO)-and is an ideal locality to study Precambrian tectonic structure. Integrated field, geochronological, and thermobarometric studies suggest that the THO was comparable to the present-day Himalayan-Karakoram-Tibet Orogen (HKTO). However, detailed understanding of the deep crustal architecture of the THO, and how it compares to that of the evolving HKTO, is lacking. The joint inversion of receiver functions and surface wave data provides new Moho depth estimates and shear velocity models for the crust and uppermost mantle of the THO. Most of the Archean crust is relatively thin (39 km) and structurally simple, with a sharp Moho; upper-crustal wave speed variations are attributed to postformation events. However, the QuebecBaffin segment of the THO has a deeper Moho (45 km) and a more complex crustal structure. Observations show some similarity to recent models, computed using the same methods, of the HKTO crust. Based on Moho character, present-day crustal thickness, and metamorphic grade, we support the view that southern Baffin Island experienced thickening during the THO of a similar magnitude and width to present-day Tibet. Fast seismic velocities at >10 km below southern Baffin Island may be the result of partial eclogitization of the lower crust during the THO, as is currently thought to be happening in Tibet.

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Lower crustal flow kept Archean continental flood basalts at sea level

Cited by 34 publications

References 26 publications

A tale of two orogens: Crustal processes in the Proterozoic Trans‐Hudson and Grenville Orogens, eastern Canada

A tale of two orogens: Crustal processes in the Proterozoic Trans‐Hudson and Grenville Orogens, eastern Canada

The contribution of metamorphic petrology to understanding lithosphere evolution and geodynamics

Seismological structure of the 1.8 Ga Trans‐Hudson Orogen of North America

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