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1. Do Continental Lithospheric Discontinuities Control Tectonic Plate Motion Directions?

   Kuiper, Yvette D (December 2024, American Geophysical Union)

   Plate-tectonic reconstructions use rotational (Euler) poles about which plates rotate in small circle patterns, producing oceanic fracture zones. Oceanic fracture zones are contiguous with transform faults. Because oceanic lithosphere older than ~200 Ma is preferentially destroyed by subduction, pre-Mesozoic plate-tectonic reconstructions lack such constraints from oceanic fracture zones. Based on high-resolution bathymetry, geological and geophysical data, with particular emphasis on the Red Sea-Gulf of Aden system, some fracture zones are shown to be contiguous with pre-existing discontinuities in adjacent continents, while others develop parallel to those. Combined with results from existing analog and numerical models, continental rift zones and oceanic spreading ridges that are initially oblique to these discontinuities are demonstrated to evolve into orientations perpendicular to them, while fracture zones and transform faults develop parallel to them. Consequently, oceanic spreading directions, or the exact plate movement directions, are controlled by pre-existing continental lithospheric discontinuities, while other factors such as slab pull control the general direction. This hypothesis constitutes a paradigm shift, from the widespread belief that transform fault and fracture zone orientations are controlled by plate motions, to one where some are inherited from pre-existing continental discontinuities and control the exact directions of plate movements. If so, identifying such discontinuities in ancient continental lithosphere may constrain plate motions in deep geologic time. 

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2. Magmatism controls global oceanic transform fault topography

   https://doi.org/10.1038/s41467-024-46197-9  

   Tian, Xiaochuan; Behn, Mark D; Ito, Garrett; Schierjott, Jana C; Kaus, Boris_J P; Popov, Anton A (December 2024, Nature Communications)

   Abstract Oceanic transform faults play an essential role in plate tectonics. Yet to date, there is no unifying explanation for the global trend in broad-scale transform fault topography, ranging from deep valleys to shallow topographic highs. Using three-dimensional numerical models, we find that spreading-rate dependent magmatism within the transform domain exerts a first-order control on the observed spectrum of transform fault depths. Low-rate magmatism results in deep transform valleys caused by transform-parallel tectonic stretching; intermediate-rate magmatism fully accommodates far-field stretching, but strike-slip motion induces across-transform tension, producing transform strength dependent shallow valleys; high-rate magmatism produces elevated transform zones due to local compression. Our models also address the observation that fracture zones are consistently shallower than their adjacent transform fault zones. These results suggest that plate motion change is not a necessary condition for reproducing oceanic transform topography and that oceanic transform faults are not simple conservative strike-slip plate boundaries. 

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3. Generation of Evolving Plate Boundaries and Toroidal Flow From Visco‐Plastic Damage‐Rheology Mantle Convection and Continents

   https://doi.org/10.1029/2023GC011179  

   Becker, Thorsten W.; Fuchs, Lukas (December 2023, Geochemistry, Geophysics, Geosystems)

   Earth's style of planetary heat transport is characterized by plate tectonics which requires rock strength to be reduced plastically in order to break an otherwise stagnant lithospheric lid, and for rocks to have a memory of past deformation to account for strain localization and the hysteresis implied by geological sutures. Here, we explore ∼10⁷Rayleigh number, visco‐plastic, 3‐D global mantle convection with damage. We show that oceanic lithosphere‐only models generate strong toroidal‐poloidal power ratios and features such as a mix of long‐wavelength tectonic motions and smaller‐scale, back‐arc tectonics driven by downwellings. Undulating divergent plate boundaries can evolve to form overlapping spreading centers and microplates, promoted and perhaps stabilized by the effects of damage with long memory. The inclusion of continental rafts enhances heat flux variability and toroidal flow, including net rotation of the lithosphere, to a level seen in plate reconstructions for the Cenozoic. Both the super‐continental cycle and local rheological descriptions affect heat transport and tectonic deformation across a range of scales, and we showcase both general tectonic dynamics and regionally applied continental breakup scenarios. Our work points toward avenues for renewed analysis of the typical, mean behavior as well as the evolution of fluctuations in geological and model plate boundary evolution scenarios. 

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4. Strike‐Slip Enables Subduction Initiation Beneath a Failed Rift: New Seismic Constraints From Puysegur Margin, New Zealand

   https://doi.org/10.1029/2020TC006436  

   Shuck, Brandon; Van Avendonk, Harm; Gulick, Sean P. S.; Gurnis, Michael; Sutherland, Rupert; Stock, Joann; Patel, Jiten; Hightower, Erin; Saustrup, Steffen; Hess, Thomas (May 2021, Tectonics)

   Abstract Subduction initiation often takes advantage of previously weakened lithosphere and may preferentially nucleate along pre‐existing plate boundaries. To evaluate how past tectonic regimes and inherited lithospheric structure might lead to self‐sustaining subduction, we present an analysis of the Puysegur Trench, a young subduction zone with a rapidly evolving tectonic history. The Puysegur margin, south of New Zealand, has experienced a transformation from rifting to seafloor spreading to strike‐slip, and most recently to incipient subduction, all in the last ∼45 million years. Here we present deep‐penetrating multichannel reflection and ocean‐bottom seismometer tomographic images to document crustal structures along the margin. Our images reveal that the overriding Pacific Plate beneath the Solander Basin contains stretched continental crust with magmatic intrusions, which formed from Eocene‐Oligocene rifting between the Campbell and Challenger plateaus. Rifting was more advanced to the south, yet never proceeded to breakup and seafloor spreading in the Solander Basin as previously thought. Subsequent strike‐slip deformation translated continental crust northward causing an oblique collisional zone, with trailing ∼10 Myr old oceanic lithosphere. Incipient subduction transpired as oceanic lithosphere from the south forcibly underthrust the continent‐collision zone. We suggest that subduction initiation at the Puysegur Trench was assisted by inherited buoyancy contrasts and structural weaknesses that were imprinted into the lithosphere during earlier phases of continental rifting and strike‐slip along the plate boundary. The Puysegur margin demonstrates that forced nucleation along a strike‐slip boundary is a viable subduction initiation scenario and should be considered throughout Earth's history. 

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5. Characterizing Marine Magnetic Anomalies: A Machine Learning Approach to Advancing the Understanding of Oceanic Crust Formation

   https://doi.org/10.1029/2024JB030682  

   Wu, S.; Thoram, S.; Sun, J.; Sager, W_W; Chen, J. (February 2025, Journal of Geophysical Research: Solid Earth)

   Abstract Linear magnetic anomalies (LMA), resulting from Earth's magnetic field reversals recorded by seafloor spreading serve as crucial evidence for oceanic crust formation and plate tectonics. Traditionally, LMA analysis relies on visual inspection and manual interpretation, which can be subject to biases due to the complexities of the tectonic history, uneven data coverage, and strong local anomalies associated with seamounts and fracture zones. In this study, we present a Machine learning (ML)‐based framework to identify LMA, determine their orientations and distinguish spatial patterns across oceans. The framework consists of three stages and is semi‐automated, scalable and unbiased. First, a generation network produces artificial yet realistic magnetic anomalies based on user‐specified conditions of linearity and orientation, addressing the scarcity of the labeled training dataset for supervised ML approaches. Second, a characterization network is trained on these generated magnetic anomalies to identify LMA and their orientations. Third, the detected LMA features are clustered into groups based on predicted orientations, revealing underlying spatial patterns, which are directly related to propagating ridges and tectonic activity. The application of this framework to magnetic data from seven areas in the Atlantic and Pacific oceans aligns well with established magnetic lineations and geological features, such as the Mid‐Atlantic Ridge, Reykjanes Ridge, Galapagos Spreading Center, Shatsky Rise, Juan de Fuca Ridge and even Easter Microplate and Galapagos hotspot. The proposed framework establishes a solid foundation for future data‐driven marine magnetic analyses and facilitates objective and quantitative geological interpretation, thus offering the potential to enhance our understanding of oceanic crust formation. 

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