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There has been a long debate about how passive (Atlantic‐type) margins can convert to active (Andean) margins, particularly if they can do so directly, or some other process such as an arc‐continent collision must intervene (Burke et al., 1984; Dewey, 1969, https://doi.org/10.1016/0012‐821x(69)90089‐2; Kusky & Kidd, 1985). Most numerical models have long‐suggested that only very young passive margins can be sites of subduction initiation since old margins become stronger as they cool and develop thick sedimentary piles during thermal subsidence (e.g., Cloetingh et al., 1982, https://doi.org/10.1038/297139a0, 1989, https://doi.org/10.1007/bf00874622; 1996; Zhong & Li, 2019, https://doi.org/10.1029/2019gl084022), whereas other analog and numerical models have suggested that old passive margins may spontaneously convert to subduction zones (e.g., Bercovici & Mulyukova, 2021, https://doi.org/10.1073/pnas.2011247118; Faccenna et al., 1999, https://doi.org/10.1029/1998jb900072; Nikolaeva et al., 2010, https://doi.org/10.1029/2009jb00654; Stern & Gerya, 2018, https://doi.org/10.1016/j.tecto.2017.10.014; Zhang et al., 2023, https://doi.org/10.1029/2023gl103553). Plain Language Summary How do passive margins convert to active margins? The evidence presented by Zeng et al. (2025), https://doi.org/10.1029/2025gc12197 and a survey of the literature about past well‐documented events overwhelmingly points to the process of arc‐polarity reversal following arc‐continent collision. The time frame of such events is such that they usually start very soon after or even during the late stages of collision, and the process is typically complete within 10–20 million years (e.g., Brown & Ryan, 2011, https://doi.org/10.1007/978‐3‐540‐88558‐0). The shortest documented cases (5–10 million years) include Timor, Taiwan, and the Proterozoic Wopmay orogen, with the longest cases (25–30 million years) including the Urals and Kohistan (Brown & Ryan, 2011, https://doi.org/10.1007/978‐3‐540‐88558‐0). Intermediate durations (∼10–12 million years) of collision to arc polarity reversal include Kamchatka, and the Grampian and Taconic collisions, as discussed above. The evidence is clear: passive margins rapidly convert to active (Andean) margins by subduction polarity reversal following arc‐continent (with passive margin) collision. Key Points Passive margins convert to active margins after collisions with arcs and subduction polarity reversal No examples are known of spontaneous subduction initiation at passive margins Zeng et al. (2025, https://doi.org/10.1029/2025gc12197) present a new example of subduction initiation and subduction polarity reversal after arc collision with passive margin

In a new study, Wu, Wang, Zhou, Zhao, Haproff, et al. (2022, https://doi.org/10.1029/2022GC010662) present a comprehensive study of the North Margin Orogen of the North China Craton (NCC), showing that older accreted rocks in this belt preserve a record of active margin magmatism from 2.2 to 2.0 Ga, followed by collisional tectonics, marked by mélange and mylonitic shear zones, then granulite facies metamorphism at 1.9–1.8 Ga, marking the final collision of the NCC with the Columbia Supercontinent. The multidisciplinary studies presented in this work support earlier suggestions that the North China Craton amalgamated during accretionary orogenesis in the Neoarchean to earlier Paleoproterozoic, and that the late widespread 1.85 Ga high‐grade metamorphism is craton‐wide in scale, and not confined to a narrow orogen in the center of the craton. This new understanding creates new possibilities for refining reconstructions of one of Earth's earliest, best documented supercontinents, showing a globally linked plate network at 1.85 Ga, and suggests drastic new correlations and models for mineral resource exploration. Key Points The Paleoproterozoic collisional orogen of the North China Craton with Columbia Supercontinent is positively identified This “North Margin Orogen (NMO)” changes reconstructions of the oldest well‐established supercontinent Correlations of the NMO with the gold‐rich Birimian of West Africa suggest a new mineral exploration strategy for China

Continental, orogenic, and oceanic lithospheric mantle embeds sizeable parcels of exotic cratonic lithospheric mantle (CLM) derived from distant, unrelated sources. This hints that CLM recycling into the mantle and its eventual upwelling and relamination at the base of younger plates contribute to the complex structure of the growing lithosphere. Here, we use numerical modeling to investigate the fate and survival of recycled CLM in the ambient mantle and test the viability of CLM relamination under Hadean to present-day mantle temperature conditions and its role in early lithosphere evolution. We show that the foundered CLM is partially mixed and homogenized in the ambient mantle; then, as thermal negative buoyancy vanishes, its long-lasting compositional buoyancy drives upwelling, relaminating unrelated growing lithospheric plates and contributing to differentiation under cratonic, orogenic, and oceanic regions. Parts of the CLM remain in the mantle as diffused depleted heterogeneities at multiple scales, which can survive for billions of years. Relamination is maximized for high depletion degrees and mantle temperatures compatible with the early Earth, leading to the upwelling and underplating of large volumes of foundered CLM, a process we name massive regional relamination (MRR). MRR explains the complex source, age, and depletion heterogeneities found in ancient cratonic lithospheric mantle, suggesting this may have been a key component of the construction of continents in the early Earth.

Plate tectonics describes the horizontal motion of rigid lithospheric plates away from midoceanic ridges and parallel to transforms, towards deep-sea trenches, where the oceanic lithosphere is subducted into the mantle. This process is the surface expression of modern-day heat loss from Earth. One of the biggest questions in Geosciences today is “when did plate tectonics begin on Earth” with a wide range of theories based on an equally diverse set of constraints from geology, geochemistry, numerical modeling, or pure speculation. In this contribution, we turn the coin over and ask “when was the last appearance in the geological record for which there is proof that plate tectonics did not operate on the planet as it does today”. We apply the laws of uniformitarianism to the rock record to ask how far back in time is the geologic record consistent with presently-operating kinematics of plate motion, before which some other mechanisms of planetary heat loss may have been in operation. Some have suggested that evidence shows that there was no plate tectonics before 800 Ma ago, others sometime before 1.8–2.7 Ga, or before 2.7 Ga. Still others recognize evidence for plate tectonics as early as 3.0 Ga, 3.3–3.5 Ga, the age of the oldest rocks, or in the Hadean before 4.3 Ga. A key undiscussed question is: why is there such a diversity of opinion about the age at which plate tectonics can be shown to not have operated, and what criteria are the different research groups using to define plate tectonics, and to recognize evidence of plate tectonics in very old rocks? Here, we present and evaluate data from the rock record, constrained by relevant geochemical-isotopic data, and conclude that the evidence shows indubitably that plate tectonics has been operating at least since the formation of the oldest rocks, albeit with some differences in processes, compositions, and products in earlier times of higher heat generation and mantle temperature, weaker oceanic lithosphere, hotter subduction zones caused by more slab-melt generation, and under different biological and atmospheric conditions.

We report partial melting of an ultrahigh pressure eclogite in the Mesozoic Sulu orogen, China. Eclogitic migmatite shows successive stages of initial intragranular and grain boundary melt droplets, which grow into a three-dimensional interconnected intergranular network, then segregate and accumulate in pressure shadow areas and then merge to form melt channels and dikes that transport magma to higher in the lithosphere. Here we show, using zircon U–Pb dating and petrological analyses, that partial melting occurred at 228–219 Myr ago, shortly after peak metamorphism at 230 Myr ago. The melts and residues are complimentarily enriched and depleted in light rare earth element (LREE) compared with the original rock. Partial melting of deeply subducted eclogite is an important process in determining the rheological structure and mechanical behaviour of subducted lithosphere and its rapid exhumation, controlling the flow of deep lithospheric material, and for generation of melts from the upper mantle, potentially contributing to arc magmatism and growth of continental crust. Natural examples of eclogite-derived migmatite were previously unknown. Here, the authors show evidence of high-pressure melting of eclogite in the Sulu orogen of China, and suggest the melts represent an exhumed example of flow channels in the lower crust, possibly a source of syn-exhumation magmas.

The coexistence of divergent (spreading ridge) and convergent (subduction zone) plate boundaries at which lithosphere is respectively generated and destroyed is the hallmark of plate tectonics. Here, we document temporally- and spatially-associated Neoarchean (2.55–2.51 Ga) rock assemblages with mid-ocean ridge and supra-subduction-zone origins from the Angou Complex, southern North China Craton. These assemblages record seafloor spreading and contemporaneous subduction initiation and mature arc magmatism, respectively, analogous to modern divergent and convergent plate boundary processes. Our results provide direct evidence for lateral plate motions in the late Neoarchean, and arguably the operation of plate tectonics, albeit with warmer than average Phanerozoic subduction geotherms. Further, we surmise that plate tectonic processes played an important role in shaping Earth’s surficial environments during the Neoarchean and Paleoproterozoic. This study reports coexisting Neoarchean divergent and convergent plate boundary rock assemblages, providing new evidence for the operation of plate tectonics 2.55–2.51 billion years ago; and also suggests the subduction zone was warm then.

The Earth’s interior and surficial systems underwent dramatic changes during the Paleoproterozoic, but the interaction between them remains poorly understood. Rocks deposited in orogenic foreland basins retain a record of the near surface to deep crustal processes that operate during subduction to collision and provide information on the interaction between plate tectonics and surface responses through time. Here, we document the depositional-to-deformational life cycle of a Paleoproterozoic foreland succession from the North China Craton. The succession was deposited in a foreland basin following ca. 2.50–2.47 Ga Altaid-style arc–microcontinent collision, and then converted to a fold-and-thrust belt at ca. 2.0–1.8 Ga due to Himalayan-style continent–continent collision. These two periods correspond to the assembly of supercratons in the late Archean and of the Paleoproterozoic supercontinent Columbia, respectively, which suggests that similar basins may have been common at the periphery of other cratons. The multiple stages of orogenesis and accompanying tectonic denudation and silicate weathering, as recorded by orogenic foreland basins, likely contributed to substantial changes in the hydrosphere, atmosphere, and biosphere known to have occurred during the Paleoproterozoic. Two different styles of orogenesis during the Neoarchean and Paleoproterozoic are recorded in the depositional-to-deformational evolution of the orogenic foreland of the North China Craton, and would have differently changed the surface environment.

The thick crust of the southern Tibetan and central Andean plateaus includes high-conductivity, low-velocity zones ascribed to partial melt. The melt origin and effect on plateau uplift remain speculative, in particular if plateau uplift happens before continental collision. The East Anatolian Plateau (EAP) has experienced similar, more recent uplift but its structure is largely unknown. Here we present an 80 km deep geophysical model across EAP, constrained by seismic receiver functions integrated with interpretation of gravity data and seismic tomographic, magnetotelluric, geothermal, and geochemical models. The results indicate a 20 km thick lower crustal layer and a 10 km thick mid-crustal layer, which both contain pockets of partial melt. We explain plateau uplift by isostatic equilibration following magmatism associated with roll-back and break-off of the Neo-Tethys slab. Our results suggest that crustal thickening by felsic melt and mafic underplate are important for plateau uplift in the EAP, Andes and Tibet. Partially molten middle and underplated lower crust may control isostatic plateau uplift, with uplift duration corelated to middle crustal thickness, which determines the height and crustal thickness of the Anatolian, Tibetan and Andean plateaux

Whether modern-style plate tectonics operated on early Earth is debated due to a paucity of definitive records of large-scale plate convergence, subduction, and collision in the Archean geological record. Archean Alpine-style sub-horizontal fold/thrust nappes in the Precambrian basement of China contain a Mariana-type subduction-initiation sequence of mid-ocean ridge basalt blocks in a 1600-kilometer-long mélange belt, overthrusting picritic-boninitic and island-arc tholeiite bearing nappes, in turn emplaced over a passive margin capping an ancient Archean continental fragment. Picrite-boninite and tholeiite units are 2698 ± 30 million years old marking the age of subduction initiation, with nappes emplaced over the passive margin at 2520 million years ago. Here, we show the life cycle of the subduction zone and ocean spanned circa 178 million years; conservative plate velocities of 2 centimeters per year yield a lateral transport distance of subducted oceanic crust of 3560 kilometers, providing direct positive evidence for horizontal plate tectonics in the Archean. How far back in time plate tectonics operated on Earth is debated because of a paucity of geological evidence for horizontal plate motions. Here the authors show that plates moved laterally by >3500 kilometres 2.7–2.5 billion years ago, demonstrating plate tectonics in the Archean Eon, when life developed on Earth.