Present Project: FORMATION, CHARACTER, HISTORY, AND BEHAVIOR OF EARTH'S OLDEST LITHOSPHERES (20   23-2027）

Project NO.: 2023-TF1

Project Leaders: T. Kusky, China and T. M. Harrison, USA

Obtaining constraints on the formation and evolution of Earth, from an early solar nebula to the present habitable planet with continental lithosphere, oceans, and an oxygen-rich atmosphere, is plagued with uncertainty but fundamentally important for understanding how deep Earth processes regulate our surface environment (Benner et al., 2019; Harrison, 2020; Miyazaki and Korenaga, 2022). Some constraints are firm: Earth was producing more heat by radioactive decay early in its history while losing primary heat acquired during planetary accretion. Our planet likely went through an early magma ocean stage, which rapidly solidified and evolved though the next 4.5 billion years to the plate-tectonic mobile-lid lithosphere that we have today. Whether this transition to a plate-tectonic Earth happened early, for instance as an immediate result of cooling of the outer crust of the magma ocean, or whether the planet evolved through different stages dominated by different mechanisms of heat loss, is one of the great unresolved questions in Earth Sciences today (O’Neill, et al., 2016; Korenaga et al., 2018, 2020; Gerya, 2019; Harrison, 2020; Brown et al., 2020). This Task Force aims at 1) obtaining a better understanding of early Earth’s tectonic regime and its relationship to planetary heat loss, and 2), determining when and by what mechanisms modern plate tectonics emerged on Earth. These topics were identified by the US National Academies (2020) as two of the greatest and most significant research frontiers for geoscientists in the next decade. Perhaps the most salient issue is determining how long the present-style mobile-lid tectonics-a system of numerous rigid plates moving relative to each other on a globally-linked network of divergent, convergent, and transform boundaries – has operated. Conversely, what other modes of planetary heat loss, such as stagnant lids, heat pipes, sagduction, or drip tectonics, operated prior to plate tectonics (Lenardic, 2018a, b; Brown and Johnson, 2018, 2019).

We will address these issues by analyzing the complete geologic (structural, metamorphic, igneous, geochemical, sedimentary, geochronologic, etc.) archive preserved in Earth’s fragmentary preserved record in ancient orogenic belts and cratons, and their geophysical expressions, to assess whether or not there is evidence for the operation of plate tectonics, including the lateral motion of plates and the resulting orogenic zonation that forms from their interactions. we will take a holistic Earth Systems approach to test the possibilities of plate tectonic vs. non-plate tectonic behavior over > 2.5 billion years of critical intervals in Earth history (Paleoarchean-Paleoproterozoic), from the North China Craton, and from the Paleo-Mesoarchean (3.6-2.9 Ga) from the Pilbara craton, and the older lithospheric relicts that may be as old as 4.2 Ga (Papineau et al., 2022; Drabon et al., 2022). Data synthesized from these cratons will be valuable for understanding the evolution of Earth’s early lithospheres, the character of the early Earth, genesis of the continental crust, its contained mineral deposits, and what conditions led to the planet’s ability to sustain life (Benner et al., 2019; Korenaga, 2018; Greber and Dauphas, 2019; Hawkesworth et al., 2020; Windley et al., 2021; Bauer et al., 2020; Turner et al., 2020; Keller and Harrison, 2020; Guo and Korenaga, 2020; Papineau et al., 2022). Lastly, we will provide encouragement and an information clearinghouse for exploration of the 15 sites beyond the Jack Hills from which >4 Ga zircons, spanning 5 continents, have been documented. None of these sites has been studied in the detail that the zircon population from Jack Hills has, leaving open a range of possibilities, including revealing a range of concomitant tectonic processes. On Earth, the age of two-thirds of the present surface (the ocean basins) is ~200 million years, less than 5% of the age of the planet. Atmospheric/aqueous-related erosion and plate tectonic recycling have resulted in the obscuration and loss of parts of Earth’s earlier geological record. Earth-like (terrestrial) planetary bodies in the Solar System (Venus, Mars, Mercury and the Moon) provide a diverse record of geological processes and events characterizing the formative years of planetary history (Head and Solomon, 1981). Stable lithospheres preserve the record of early crust and lithosphere formation, mantle convection patterns, impact processes, lithospheric heat loss mechanisms, and the historical cadence of these factors as revealed in their geological records. Venus, the most Earth-like of the terrestrial planets (Ivanov and Head, 2011), has a mean surface age similar to Earth’s, but no active plate tectonics, perhaps representing a framework of pre-plate tectonic history on Earth. We will call on these “planetary perspectives” to widen the parameter space of the plausible origin and configuration of Earth’s oldest lithospheres. By focusing the community on these questions, we will address key problems of the nature and evolution of early Earth, and the initiation time, mechanism, and style of plate tectonics, and linkages between the Deep Earth in Deep Time in Deep Space, and its links to Earth Surface Systems including development of the early biosphere.

Reference:

Bauer, A.M., Reimink, J.R., Chacko, T., Foley, B.J., Shirey, S.B., Pearson, D.G., 2020. Hafnium isotopes in zircons document the gradual onset of mobile-lid tectonics. Geophysical Perspectives Letters 14, 1-6. https://doi.org/10.7185/geochemlet.2015.

Brenner, A.R., Fu., R.R., Evans, D.A.D., Smirnov, A.V., Trubko, R., Rose, I.R., 2020. Paleomagnetic evidence for modern-like plate motion velocities at 3.2 Ga. Science Advances 6, eaaz8670. https://doi.org/10.1126/sciadv.aaz8670.

Brown M, Johnson T. 2018. Secular change in metamorphism and the onset of global plate tectonics. American Mineralogist 103, 181-196. https://doi.org/10.2138/am-2018-6166.

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Drabon, N., Byerly, B.L., Byerly, G.R., Wooden, J.L., Wiedenbeck, M., Valley, J.W., Kitajima, K., Bauer, A., Lowe, D.R., 2022. Destabilization of long-lived Hadean protocrust and the onset of pervasive hydrous melting at 3.8 Ga. AGU Advances 3, e2021AV000520. https://doi.org/10.1029/2021AV000520.

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Greber, N.D., Dauphas, N., 2019. The chemistry of fine-grained terrigenous sediments reveals a chemically evolved Paleoarchaean emerged crust. Geochimica et Cosmochimica Acta 255, 247–264. https://doi.org/10.1016/j.gca.2019.04.012.

Guo, M., Korenaga, J., 2020. Argon constraints on the early growth of felsic continental crust. Science Advances 6, 1-10. https://doi.org/10.1126/sciadv.aaz6234.

Hawkesworth, C.J., Cawood, P.A., Dhuime, B., 2020. The evolution of the continental crust and the onset of plate tectonics. Frontiers in Earth Science. https://doi.org/10.3389/feart.2020.00326.

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Keller, C.B., Harrison, T. M., 2020. Constraining the crustal silica on ancient Earth. Proceedings of National Academy of Sciences, pnas.org/cgi/doi/10.1073/pnas.2009431117.

Korenaga, J., 2018. Crustal evolution and mantle dynamics through Earth history. Philosophical Transactions of the Royal Society of London A376, 20170408. http://dx.doi.org/10.1098/rsta.2017.0408.

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Lenardic, A., 2018b. The diversity of tectonic modes and thoughts about transitions between them, Philosophical Transactions of the Royal Society A 376, 20170416. http://dx.doi.org/10.1098/rsta.2017.0416.

Miyazaki, Y., and Korenaga, J., 2022. A wet heterogeneous mantle creates a habitable world in the Hadean. Nature 603, https://doi.org/10.1038/s41586-021-04371-9.

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Turner, S., Wilde, S., Wörner, G., Schaefer, B., Lai, Y.J., 2020. An andesitic source for Jack Hills zircon supports onset of plate tectonics in the Hadean. Nature Communications 11:1241. https://doi.org/10.1038/s41467-020-14857-1.

Windley, B.F., Kusky, T.M., and Polat, A., 2021, Onset of plate tectonics by the Eoarchean. Precambrian Research. https://doi.org/10.1016/j.precamres.2020.105980.