Tectonics of early Earth: Some geodynamic considerations

Hunen, Jeroen van; Keken, Peter E. van; Hynes, Andrew; Davies, Geoffrey F.

doi:10.1130/2008.2440(08)

Cited by 21 publications

(19 citation statements)

References 114 publications

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“…Stern 2005;Cawood et al 2006). A range of geological, geodynamic and geochemical constraints (recently summarized by Condie & Kroner 2008;Shirey et al 2008;van Hunen et al 2008), suggest the strong likelihood of plate tectonic behaviour in the Palaeoproterozoic and possibly back into the Archaean; an inference also made by Brown (2007) based on the presence of characteristic high pressure -lower temperature and high temperature -lower pressure metamorphic mineral assemblages associated with subduction and arcs respectively (Fig. 1h).…”

Section: Supercontinentsmentioning

confidence: 99%

Palaeoproterozoic supercontinents and global evolution: correlations from core to atmosphere

Reddy

Evans

2009

115

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The Palaeoproterozoic era was a time of profound change in Earth evolution and represented perhaps the first supercontinent cycle, from the amalgamation and dispersal of a possible Neoarchaean supercontinent to the formation of the 1.9-1.8 Ga supercontinent Nuna. This supercontinent cycle, although currently lacking in palaeogeographic detail, can in principle provide a contextual framework to investigate the relationships between deep-Earth and surface processes. In this article, we graphically summarize secular evolution from the Earth's core to its atmosphere, from the Neoarchaean to the Mesoproterozoic eras (specifically 3.0-1.2 Ga), to reveal intriguing temporal relationships across the various 'spheres' of the Earth system. At the broadest level our compilation confirms an important deep-Earth event at c. 2.7 Ga that is manifested in an abrupt increase in geodynamo palaeointensity, a peak in the global record of large igneous provinces, and a broad maximum in several mantle-depletion proxies. Temporal coincidence with juvenile continental crust production and orogenic gold, massive-sulphide and porphyry copper deposits, indicate enhanced mantle convection linked to a series of mantle plumes and/or slab avalanches. The subsequent stabilization of cratonic lithosphere, the possible development of Earth's first supercontinent and the emergence of the continents led to a changing surface environment in which voluminous banded iron-formations could accumulate on the continental margins and photosynthetic life could flourish. This in turn led to irreversible atmospheric oxidation at 2.4-2.3 Ga, extreme events in global carbon cycling, and the possible dissipation of a former methane greenhouse atmosphere that resulted in extensive Palaeoproterozoic ice ages. Following the great oxidation event, shallow marine sulphate levels rose, sediment-hosted and iron-oxide-rich metal deposits became abundant, and the transition to sulphide-stratified oceans provided the environment for early eukaryotic evolution. Recent advances in the geochronology of the global stratigraphic record have made these inferences possible. Frontiers for future research include more refined modelling of Earth's thermal and geodynamic evolution, palaeomagnetic studies of geodynamo intensity and continental motions, further geochronology and tectonic syntheses at regional levels, development of new isotopic systems to constrain geochemical cycles, and continued innovation in the search for records of early life in relation to changing palaeoenvironments.

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Section: Supercontinentsmentioning

confidence: 99%

Palaeoproterozoic supercontinents and global evolution: correlations from core to atmosphere

Reddy

Evans

2009

115

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“…Van Hunen et al . [] conclude that the Archean mantle was only 100–300 K hotter than the present‐day mantle, which is in good agreement with our results (Figure , fourth panel). From this it follows, in accordance with Gurnis and Davies ], that we can abandon the idea of mantle wide, simultaneous sets of thermal or chemical overturns that alter the overall thermal structure of the mantle relatively rapidly.…”

Section: Resultsmentioning

confidence: 99%

Real episodic growth of continental crust or artifact of preservation? A 3‐D geodynamic model

Walzer

Hendel

2013

JGR Solid Earth

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[1] We investigate whether the observed zircon age distribution of continental crust (CC) is produced by real crustal growth episodes or is only an artifact of preservation. In connection with the second alternative of this question, other authors proposed that there was little episodicity in the production of new CC and that modeling corroborates this opinion. We conclude that a combination of the two answers might be possible. In matters of modeling, however, we ascertain that a dynamic modeling of the convection-differentiation system of the mantle reveals the high probability of magmatic episodes. We solve the full set of balance equations in a 3-D spherical-shell mantle. The heat-producing elements are redistributed by chemical differentiation. A realistic solidus model of mantle peridotite is essential for an applicable model. The solidus depends not only on depth but also on the volatile concentration. Furthermore, we introduced realistic profiles of Grüneisen parameter, viscosity, adiabatic temperature, thermal expansivity, and specific heat. Our model automatically produces lithospheric plates and growing continents. Regarding number, size, form, distribution, and surface velocity of the continents, no constraints have been prescribed. Regions of the input parameter space (Ra, y , k, f 3 ) that are favorable with respect to geophysical quantities show simultaneously not only episodicity of CC growth but also a reproduction of the observed zircon-age maxima referring to the instants of time. We also obtain Archean events for ages greater than 3000 Ma that are not or scarcely visible in the observed zircon ages. Sinusoidal parts of the evolution curve of qob, Ur, and E kin are superposed with a monotonous decrease. The volumetrically averaged mantle temperature, T mean , however, decreases smoothly and slowly, nearly without pronounced variations. Therefore, we can dismiss catastrophic mechanisms that simultaneously incorporate the whole mantle.

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“…de Wit et al, 1987Wit et al, , 1992Furnes et al, 2007;Komiya et al, 1999;Kusky et al, 2001Kusky et al, , 2013Polat et al, 2002) whereas non-uniformitarians propose tectonic models peculiar to the early Earth (e.g. Bédard, 2006;Hickman, 2004;Kröner, 1985;van Hunen et al, 2008;Zegers and van Keken, 2001). In addition, the relationship between greenstone belts and ambient granitoid batholiths is also controversial; some propose that basaltic lava and chemical sediments in the greenstone belts were allochthonous, and were intruded by young granitoid batholiths after their emplacement (e.g.…”

Section: Depositional Environment Of the Nulliak Supracrustal Rocks Amentioning

confidence: 95%

Geology of the Eoarchean, > 3.95 Ga, Nulliak supracrustal rocks in the Saglek Block, northern Labrador, Canada: The oldest geological evidence for plate tectonics

et al. 2015

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The Earth is a unique planet, which has been highly evolved, diversified and complicated through geologic time, and underwent many key events, including giant impact, magma ocean, core formation, large-scale mantle differentiation and late heavy bombardment, especially in its dawn. But, our knowledge of early Earth is limited due to the lack of the Hadean supracrustal rocks. The supracrustal rocks with the Eoarchean ages provide key evidence for the Earth's early evolution, but few supracrustal rocks have been comprehensively investigated. Therefore, we mapped in seven areas of the Saglek Block, northern Labrador, where ancient supracrustal sequences are interleaved with a diverse assemblage of orthogneisses. Early studies suggested that some of them have the Mesoarchean ages because of the lack of the Mesoarchean Saglek dyke, but we found the Saglek dykes in the areas to recognize the Eoarchean Nulliak supracrustal rocks and Uivak Gneiss in all the areas. Recent reassessment of U-Pb dating and cathodoluminescence observation of zircons from the oldest suites of the Uivak Gneiss showed that the Uivak Gneiss has the Eoarchean age, N 3.95 Ga, and forms the Iqaluk-Uivak Gneiss series. Because our geological survey clearly showed that the Iqaluk-Uivak Gneisses were intruded into the Nulliak supracrustal belts, the Nulliak supracrustal rocks are the oldest supracrustal rock in the world. The supracrustal belts consist of piles of fault-bounded blocks, which are composed of the ultramafic rocks, mafic rocks and sedimentary rocks in ascending order, similar to modern ocean plate stratigraphy (OPS). In addition, small-scale duplex structures are found over the areas. The presence of duplex structure and OPS indicates that the N 3.95 Ga Nulliak supracrustal belts originate from an accretionary complex. The presence of the accretionary complex, ophiolite and granitic continental crust provides the oldest evidence for the plate tectonics on the early Earth.

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Tectonics of early Earth: Some geodynamic considerations

Cited by 21 publications

References 114 publications

Palaeoproterozoic supercontinents and global evolution: correlations from core to atmosphere

Palaeoproterozoic supercontinents and global evolution: correlations from core to atmosphere

Real episodic growth of continental crust or artifact of preservation? A 3‐D geodynamic model

Geology of the Eoarchean, > 3.95 Ga, Nulliak supracrustal rocks in the Saglek Block, northern Labrador, Canada: The oldest geological evidence for plate tectonics

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