Abstract Understanding of secular evolution of the Earth system is based largely on the rock and mineral archive preserved in the continental lithosphere. Based on the frequency and range of accessible data preserved in this record, we divide the secular evolution into seven phases: (a) “ Proto‐Earth ” (ca. 4.57–4.45 Ga); (b) “ Primordial Earth ” (ca. 4.45–3.80 Ga); (c) “ Primitive Earth ” (ca. 3.8–3.2 Ga); (d) “Juvenile Earth ” (ca. 3.2–2.5 Ga); (e) “ Youthful Earth ” (ca. 2.5–1.8 Ga); (f) “ Middle Earth ” (ca. 1.8–0.8 Ga); and (g) “ Contemporary Earth ” (since ca. 0.8 Ga). Integrating this record with knowledge of secular cooling of the mantle and lithospheric rheology constrains the changes in the tectonic modes that operated through Earth history. Initial accretion and the Moon forming impact during the Proto‐Earth phase likely resulted in a magma ocean. The solidification of this magma ocean produced the Primordial Earth lithosphere, which preserves evidence for intra‐lithospheric reworking of a rigid lid, but which also likely experienced partial recycling through mantle overturn and meteorite impacts. Evidence for craton formation and stabilization from ca. 3.8 to 2.5 Ga, during the Primitive and Juvenile Earth phases, likely reflects some degree of coupling between the convecting mantle and a lithosphere initially weak enough to favor an internally deformable, squishy‐lid behavior, which led to a transition to more rigid, plate like, behavior by the end of the early Earth phases. The Youthful to Contemporary phases of Earth, all occurred within a plate tectonic framework with changes between phases linked to lithospheric behavior and the supercontinent cycle.
The Earth has evolved into a habitable planet through ongoing and complex cycling. Decades of field studies, geochemical analyses and computational approaches to integrate data into feasible geodynamic models reveal that Earth’s evolution was not linear but evolved in discrete phases. The timing of changes between these phases, their loci within Earth’s crust or between discrete cratonic terranes, and most importantly the drivers or tipping point for these changes, remain elusive.Integrating the record from the continental archive with knowledge of the ongoing cooling of the mantle and lithospheric rheology (parametrized for its evolving thermal state) allows us to determine that a number of different tectonic modes operated through the early history of the Earth. The temporal boundaries between these proposed different phases in tectonic mode are approximate, transitional, and correspond with the first recording of a key feature of that phase.Initial accretion and the moon forming impact resulted in a proto-Earth phase (ca. 4.57-4.45 Ga) likely characterized by a magma ocean. Its solidification produced the primitive Earth lithosphere that extended from ca. 4.45-3.80 Ga, which based on the very minor fragments preserved in younger cratons provides evidence for intra-lithospheric reworking, but which also likely involved intermittent and partial recycling of the lid through mantle overturn and meteoritic impacts. Evidence for craton formation and stabilization during the primitive (ca. 3.8 Ga to 3.2 Ga), and juvenile (ca. 3.2 Ga to 2.5 Ga) phases of Earth evolution likely reflects some degree of coupling between the convecting mantle and a lithosphere initially weak enough to favour an internally deformable, squishy-lid behaviour. These regions of deformable lithosphere likely oscillated spatially and temporally with regions of more rigid, plate like, behaviour leading to a transition to global plate tectonics by the end of the Archean (ca. 2.5 Ga). Evidence for assembly of rigid cratonic blocks in the late Archean along with their subsequent rifting and breakup followed by their reassembly along major linear orogenic belts in the Paleoproterozoic marks the clear inception of the supercontinent cycle in response to a plate tectonic framework of oceans opening and closing.Since solidification of the magma ocean early in Earth history, the available record suggests some degree of mantle-lithosphere coupling. The development and stabilization of cratons from 3.8-2.5 Ga provides evidence for the progressive development of rigid lithosphere and represents the inexorable precursor to the development of plate tectonics.
Earth and Space Science Open Archive PosterOpen AccessYou are viewing the latest version by default [v1]Weaker lithospheric dripduction into Archean TTG crust formationAuthorsPrasanna M.GunawardanaiDGabrieleMorraiDPriyadarshiChowdhuryPeter A.CawoodiDSee all authors Prasanna M. GunawardanaiDCorresponding Author• Submitting AuthorSchool of EarthAtmosphere and EnvironmentMonash UniversityAustraliaiDhttps://orcid.org/0000-0003-1875-011Xview email addressThe email was not providedcopy email addressGabriele MorraiDDepartment of Physics and School of GeoSciences, University of Louisiana at Lafayette, USAiDhttps://orcid.org/0000-0002-0787-6107view email addressThe email was not providedcopy email addressPriyadarshi ChowdhurySchool of Earth, Atmosphere and Environment, Monash University, Australiaview email addressThe email was not providedcopy email addressPeter A. CawoodiDSchool of Earth, Atmosphere and Environment, Monash University, AustraliaiDhttps://orcid.org/0000-0003-1200-3826view email addressThe email was not providedcopy email address
<p>The tectonic regime of the early Earth is crucial to understand how interior and exterior elements of the Earth interacted to make our planet habitable (Cawood et al., 2018). Our understanding of the processes involved is far from complete, particularly about how the switch between non-plate tectonic and plate tectonic regimes may have happened during the Archean. In this study, we investigate how Archean subduction events (albeit isolated and intermittent) may have evolved within/from a stagnant-lid regime. We perform 2D numerical modelling of mantle convection (using Underworld2) under a range of conditions appropriate for the early-to-mid Archean Earth including hotter mantle potential temperature and internal heat production. Using the models, we evaluate how the mantle temperature and viscosity, buoyancy force, surface heat flow and surface velocity may have evolved over a duration of ~800-1000 million years.</p><p>Our models indicate that lithospheric drips are an efficient way of releasing a large amount of heat from the Earth&#8217;s surface over a short period of time. Repeated occurrences of dripping events result in average mantle temperature gradually decreasing. Concomitant with this thermal evolution, the drip dimensions grew to form large, symmetrical drips as well as occasional, asymmetric subduction type events. The subduction events lead to large-scale resurfacing of the lithosphere. We surmise that the decreasing of average mantle temperature: (1) increases the temperature dependent viscosity of the mantle, and 2) decreases the buoyancy forces of mantle convection. Both these factors lower the convective vigour and increases the lithospheric (the upper thermal boundary layer) thickness via decreasing the effective Rayleigh number. These changes in the lithosphere-asthenosphere system facilitate the transition from a dripping dominated regime to a mix of large-dripping and intermittent subduction regime over a period of ~1 billon years. This change in tectonic setting is predicted to alter surface velocity patterns, surface heat flux and production rate of felsic magmas, which allows the modelling results can be tested against the rock record.</p><p>Reference</p><p>Cawood, P. A., Hawkesworth, C. J., Pisarevsky, S. A., Dhuime, B., Capitanio, F. A., and Nebel, O., 2018, Geological archive of the onset of plate tectonics: Philosophical transactions. Series A, Mathematical, physical, and engineering sciences, v. 376, no. 2132.</p>
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