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At the altitude of low-Earth-orbiting satellites, most details of lithospheric magnetic anomalies observed near surface are attenuated, and only slowly decaying long-wavelength magnetic anomalies can be detected. Long-wavelength magnetic anomalies are generated by large-scale magnetized rocks in the Earth's crust and uppermost mantle at depths shallower than the Curie depth. Interpretation of such lithospheric magnetic anomalies has been used in geological mapping, crustal composition and structure studies, plate tectonic reconstruction, and geodynamics. To introduce the origin of long-wavelength magnetic anomalies at a global scale, we first reviewed satellite magnetic anomaly maps in early periods and calculated anomaly maps using four main lithospheric magnetic field models, including the CHAOS-7, CM6, MF7, and CSES models. Then, based on the result of the CHAOS-7 model at 500 km altitude, 29 long-wavelength magnetic anomalies with amplitudes greater than 4 nT were identified and their geological origins were reviewed. Among these, there were twenty magnetic anomalies over continents and nine over the ocean. The long-wavelength magnetic anomalies over continental areas were mostly located in Precambrian basements related to the Archean nuclei, Proterozoic terrane, and iron-rich formations, with a few located in the orogenic background. The long-wavelength magnetic anomalies in the ocean region were all located in oceanic plateau, generally related to the breakup of Gondwana during the Cretaceous Period, and have the characteristics of thickened crust. Hence, the long-wavelength magnetic anomalies reveal a significant magnetization difference in the deep crust during crustal growth, a key issue that requires further study. Compared to satellite magnetic surveys in some other nations, detecting lithospheric magnetic anomalies by satellite started relatively late in China. The China Seismo-Electromagnetic Satellite (CSES) was launched in February 2018. It was China's first satellite designed to monitor earthquakes with multiple geophysical payloads, including magnetometers capable of measuring weak signals from the lithosphere. The Macau Science Satellite-1 (MSS-1) was launched in 2023 and is specially used for monitoring the geomagnetic field in low latitudes. Furthermore, a subsequent CSES-02 satellite is planned to be launched in 2024. With the vigorous development of satellite magnetic surveys in China, it is expected that progressively more Chinese researchers will pay attention to long-wavelength magnetic anomalies and promote the study of their origin.

Copyright of Advances in Earth Science (1001-8166) is the property of Advances in Earth Science Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

A small tonalite – dacite body has been discovered in the Nakanogawa Group, Hidaka Belt, northern Japan, which is a Palaeogene subduction complex formed in the palaeo-Japan trench along the northeastern margin of Eurasia. The tonalites are characterized by extremely low K2O (0.2–0.3 wt.%) and relatively flat chondrite-normalized rare earth element patterns (La/Yb[N] ~2.3), similar to plagiogranites in ophiolites. The major-and trace-element characteristics are consistent with low-pressure partial melting of oceanic crust outside the garnet stability field. Zircon U – Pb dating of the tonalite yielded a weighted-mean 206Pb/238U age of 159.1 ± 1.6 Ma. Late Jurassic oceanic plateau-type basaltic rocks with a small amount of plagiogranitic rocks are distributed sporadically in subduction complexes along the palaeo-Japan arc – trench system. A similar zircon U – Pb age (151.6 ± 1.8 Ma) has been reported for greenstone in the Cretaceous subduction complex along the palaeo-Kuril arc – trench system. The tonalite – dacite block was probably derived from the subduction complex at the junction of the palaeo-Japan and -Kuril arc – trench systems. Thus, the greenstones and the tonalite body were likely part of a large oceanic plateau, which formed at the Izanagi – Pacific–Farallon ridge triple junction during the Late Jurassic – Early Cretaceous. [ABSTRACT FROM AUTHOR]

[Display omitted] • Late Mesozoic seamounts are independent from paleo-Pacific subduction system. • An oceanic plateau in the Northeastern SCS margin. • Buoyant oceanic plateau led to the cessation of paleo-Pacific subduction process. The Northern South China Sea (SCS) margin experienced the switch from Andean-type active subduction to passive extension during late Mesozoic era. However, the mechanism of cessation of paleo-Pacific subduction in the SCS region is unclear, and the location of suture zone between paleo-Pacific plate and South China block is obscure. In this study, we report new 40Ar/39Ar ages and whole-rock Hf isotopes of basalts from two poorly studied volcanic seamounts (namely, Puyuan and Beipo) at the ocean-continent transition zone in the Northeastern SCS margin, with an emphasis on the existence of exotic, buoyant oceanic plateau and its geodynamic effect on subduction cessation. Results indicate that the OIB-type Puyuan and E-MORB-type Beipo volcanic seamounts were erupted at 154.1 Ma and 93.2 Ma, respectively. Whole-rock trace element, Sr-Nd-Pb-Hf isotopic compositions, and subduction polarity point out that these samples were oceanic intraplate basalts formed within the paleo-Pacific plate, independent of the coeval, Late Mesozoic paleo-Pacific subduction system in the region. The ages and geochemical data of the two volcanic seamounts, combined with geochemical data of Late Mesozoic Pacific oceanic plateaus and seismic data of the Northeastern SCS margin, show that there may exist a Late Mesozoic exotic, buoyant oceanic plateau in the region. The collision between the oceanic plateau and the South China block could lead to the cessation of paleo-Pacific plate subduction, and changes in tectonic regime during the Late Cretaceous era (ca. 100–65 Ma). The pre-existing, Late Mesozoic suture zone has been well constrained by the remnant oceanic plateau and continental arc, and may play a key role in the formation of Cenozoic rifting tectonic units in the region. [ABSTRACT FROM AUTHOR]

Valdivia Bank (VB) is a Late Cretaceous oceanic plateau formed by volcanism from the Tristan‐Gough hotspot at the Mid‐Atlantic Ridge (MAR). To better understand its origin and evolution, magnetic data were used to generate a magnetic anomaly grid, which was inverted to determine crustal magnetization. The magnetization model reveals quasi‐linear polarity zones crossing the plateau and following expected MAR paleo‐locations, implying formation by seafloor spreading over ∼4 Myr during the formation of anomalies C34n‐C33r. Paleomagnetism and biostratigraphy data from International Ocean Discovery Program Expedition 391 confirm the magnetic interpretation. Anomaly C33r is split into two negative bands, likely by a westward ridge jump. One of these negative anomalies coincides with deep rift valleys, indicating their age and mechanism of formation. These findings imply that VB originated by seafloor spreading‐type volcanism during a plate reorganization, not from a vertical stack of lava flows as expected for a large volcano. Plain Language Summary: Oceanic plateaus are large, elevated underwater features commonly formed from volcanic material from a hotspot. Valdivia Bank is a Late Cretaceous oceanic plateau in the southeast Atlantic Ocean formed by volcanism from the Tristan‐Gough hotspot near the Mid‐Atlantic Ridge. The origin and evolution of Valdivia Bank is poorly defined, but new magnetic data suggests the edifice originated through ridge‐centered volcanism, with lateral accretion of crust. This is unlike the evolution of a massive volcano, which would be expected to create a vertical stack of lava flows. Magnetic inversion modeling suggests the plateau was formed by seafloor spreading during the formation of anomalies C34n‐C33r, with the plateau becoming younger from east to west, rather than north‐south as predicted by some hotspot models. Results from International Ocean Discovery Program Expedition 391 paleomagnetism and biostratigraphy confirm the anomaly interpretation. Key Points: Valdivia Bank is characterized by quasi‐linear magnetic anomalies that are parallel to the inferred paleo‐Mid‐Atlantic RidgeMagnetic anomalies imply that the plateau becomes younger E‐W consistent with formation via seafloor spreading during anomalies C34n‐C33rRift valleys, division of C33r, and anomaly curvature imply complex ridge tectonics and a ridge jump [ABSTRACT FROM AUTHOR]

Flat subduction can significantly influence the distribution of volcanism, stress state, and surface topography of the overriding plate. However, the mechanisms for inducing flat subduction remain controversial. Previous two-dimensional (2-D) numerical models and laboratory analogue models suggested that a buoyant impactor (aseismic ridge, oceanic plateau, or the like) may induce flat subduction. However, three-dimensional (3-D) systematic studies on the relationship between flat subduction and buoyant blocks are still lacking. Here, we use a 3-D numerical model to investigate the influence of the aseismic ridge, especially its width (which is difficult to consider in 2-D numerical models), on the formation of flat subduction. Our model results suggest that the aseismic ridge needs to be wide and thick enough to induce flat subduction, a condition that is difficult to satisfy on the Earth. We also find that the subduction of an aseismic ridge parallel to the trench or a double aseismic ridge normal to the trench has a similar effect on super-wide aseismic ridge subduction in terms of causing flat subduction, which can explain the flat subduction observed beneath regions such as Chile and Peru.

The Tamu Massif, considered the biggest single volcano on Earth, was formed by the accumulation of enormous amounts of magma erupting to the surface. It is the largest and oldest seamount in Shatsky Rise, which is the third largest oceanic plateau on Earth. However, the formation mechanism of Tamu Massif is still controversial because evidence point to different formation hypotheses. In this paper, we applied the P-wave coda autocorrelation method and used the hydrophone waveform data acquired by the ocean bottom seismometer (OBS) deployed on Tamu Massif to constrain the oceanic crust, and these results provide new finding on the structure of the oceanic crust for Tamu Massif. We hope it can provide some implications to research the formation mechanism of Tamu Massif. These results show that some stations in Tamu Massif received reflection signals from shallower depths that are nearly parallel to the seafloor. We infer that in the shallow oceanic crust, there is a layer composed of alternating eruptions of dense, higher velocity massive lava and sparse, lower velocity pillow lava flows, which have less density and lower velocity compared to the lower oceanic crust, with a strong acoustic impedance contrasts between them and thus able to generate a reflection signal, which is observed in our autocorrelation results.

Abstract Valdivia Bank (VB) is a Late Cretaceous oceanic plateau formed by volcanism from the Tristan‐Gough hotspot at the Mid‐Atlantic Ridge (MAR). To better understand its origin and evolution, magnetic data were used to generate a magnetic anomaly grid, which was inverted to determine crustal magnetization. The magnetization model reveals quasi‐linear polarity zones crossing the plateau and following expected MAR paleo‐locations, implying formation by seafloor spreading over ∼4 Myr during the formation of anomalies C34n‐C33r. Paleomagnetism and biostratigraphy data from International Ocean Discovery Program Expedition 391 confirm the magnetic interpretation. Anomaly C33r is split into two negative bands, likely by a westward ridge jump. One of these negative anomalies coincides with deep rift valleys, indicating their age and mechanism of formation. These findings imply that VB originated by seafloor spreading‐type volcanism during a plate reorganization, not from a vertical stack of lava flows as expected for a large volcano.

In this study, we for the first time applied a joint geodynamic‐geophysical inversion approach to oceanic plateau subduction models, and compared the subduction style and corresponding topography and Bouguer gravity of two representative subduction scenarios with passive or active collision. We showed that the case of passive collision of the Ontong Java Plateau (OJP) crust better explains the topography, gravity, and seismic data than the active collision scenario. This implies that the OJP did not control the regional dynamics during the collisional process. We conclude that previous studies may have overestimated the role of the OJP in triggering subduction initiation, subduction polarity reversal, and even Pacific Plate rotation. Plain Language Summary: The effect of the Ontong Java Plateau (OJP), the largest oceanic plateau on Earth, on subduction dynamics remains controversial. Proposed models for the evolution of the OJP range from dominantly "soft docking" that generates shallow subduction and little impact on nearby regions, to strong and active collision that results in deep plateau subduction, extensive accretion, subduction polarity reversal, and even major plate reorganization. Determining the subduction depth and accretion volume of OJP is the key to resolving this dispute. In the former, the oceanic plateau undergoes shallow subduction with its upper and middle crusts slightly accreted into the island arc, leading to relatively low topography and a flat Bouguer gravity profile, consistent with observation. The latter case leads to deep subduction of the plateau lithosphere, resulting in high topography, low Bouguer gravity, and crustal structures that all violate observation. Key Points: The joint geodynamic‐geophysical inversion approach can help distinguish ambiguous dynamic behaviors of oceanic plateau subductionThe Bouguer gravity and other observations of Ontong Java Plateau (OJP) favor the passive collision model over the active collision modelOJP should have played a passive role in the collision process, implying the overestimation in previous studies [ABSTRACT FROM AUTHOR]

The formation and geology of oceanic plateaus are incompletely understood, in part because geophysical data are sparse and of low density. This paper presents an improved high‐resolution bathymetry map for southern Shatsky Rise, by combining newly acquired multibeam bathymetry data from several cruises and by filling in gaps in multibeam coverage with the SRTM15+ global bathymetry model. This map provides important insights on the evolution of Shatsky Rise from plateau forming, to post‐plateau secondary volcanism, to sedimentation, erosion, and sedimentary mass wasting. Tamu Massif is segmented by several subdued bathymetric troughs that divide the massif flanks into smaller rises. The segmentation pattern suggests Tamu Massif was built by a series of eruptions along a jumping triple junction. The distribution of secondary volcanic cones is non‐uniform, with most occurring on the southern and eastern flanks. Most of these secondary cones occur as short chains that parallel nearby magnetic lineations, suggesting control by spreading ridge parallel faults. These results suggest the evolution of Shatsky Rise was largely controlled by spreading ridges during its active volcanic phase. Numerous escarpments were identified around the plateau, a majority of which parallel bathymetry contours, suggesting these features developed because of differential subsidence of the rise massifs. The map reveals widespread mass wasting and downslope sediment movement, shifting sediment distribution and changing the surface morphology. Improved topography improves our understanding of the evolution of Shatsky Rise and emphasizes the importance of bathymetry data in deciphering the geodynamic evolution of large igneous provinces. Plain Language Summary: Shatsky Rise is a large oceanic plateau located in northwest Pacific Ocean offshore Japan. It formed from hotspot volcanism that erupted along a moving triple junction, forming volcanic mountains along the way, of which Tamu Massif and Ori Massif are the largest. We present new high‐resolution bathymetry map of southern Shatsky Rise by merging newly available multibeam data with existing data and filling gaps in coverage with ba/thymetry estimated from satellite altimetry. Studies considered Tamu Massif as a large edifice formed from voluminous ridge‐centered eruptions. However, the map reveals Tamu Massif to be segmented by several shallow valleys that divide it into five smaller mountains, each forming at a jumping triple junction, suggesting that Tamu Massif was built by a series of ridge‐centered eruptions. The map also shows non‐uniform distribution of secondary volcanic cones over Tamu Massif, majority of them located over eastern and southeastern flanks due to preferential volcanism occurring near the Pacific‐Farallon ridge. When a volcano becomes dormant, it becomes covered with sediments, a process often thought to be simple accumulation. We discovered evidence of substantial sedimentary movement that has occurred and is likely still occurring, suggesting that volcano morphology can significantly vary long after it becomes volcanically inactive. Key Points: We present a high‐resolution bathymetry map of southern Shatsky Rise with greater multibeam coverage revealing small‐scale surface featuresTamu Massif is subtly segmented into 5 smaller rises consistent with formation by series of ridge eruptions along a jumping triple junctionSecondary volcanic cones are distributed mainly over the southern and eastern flanks, and many have trends implying spreading ridge control [ABSTRACT FROM AUTHOR]

The nature of the early Archean ocean floor remains a topic of important debate. There are relatively few well-preserved occurrences worldwide where such terrains may be studied in detail because of structural dismemberment, metamorphic overprinting and pervasive early stage hydrothermal alteration to recent weathering. The 3.41-Ga dominantly mafic formations of the Nondweni Greenstone Belt (NGB) covering 270 km2 in the south-eastern Kaapvaal Craton comprise submarine volcanics that exhibit a wide range of textural features, including pillows, chill zones and brecciated flow tops, and various spinifex textures, including the rare platy pyroxene type, cumulate layers, and tuffs. Channelized subaqueous lava lakes that underwent fractionation are capped by thick spinifex-textured units and pillows. Early stage seafloor alteration is regionally variable, ranging from intense to minimal, with preservation of original mineralogy in many areas. Mafic volcanic rocks of the NGB contrast with those of the Barberton Greenstone Belt both in the style of volcanism and in the associated compositional range of komatiitic basalt to basalt with a complete absence of high-Mg komatiites. Olivine-phyric rocks, or derivatives thereof, are largely absent and pyroxene is the main controlling phase with orthopyroxene in the most primitive komatiitic basalts and clinopyroxene in the evolved lava lake sequences. The abundance of orthopyroxene typifies the long-standing silica-enriched character of the Kaapvaal Craton. Three exceptionally well-preserved and well-exposed sequences were studied utilizing hand-drilled samples and deep coring providing unprecedented stratigraphic and textural detail and field controls for more than 400 samples. A unifying feature of the mafic volcanics of the NGB is the range of compositions and ratios of incompatible elements most clearly illustrated by a series of high- and low-Ti compositional lineages reflecting differing sources or degrees of mantle partial melting. Sharp boundaries between high- and low-Ti flow successions indicate sudden changes in the melting regimes or the interaction of flow sequences from different volcanic centres. Th/Nb ranges from 0.1 to 0.2 and reveals crustal contamination of primitive lavas. The primary magma that gave rise to the most primitive komatiitic basalts with 19.5% MgO was derived from partial melting of a mantle plume source in the garnet stability field. Trace element modeling shows that the sequences studied in detail have been modified by fractionation and crustal contamination with the most likely contaminant being the Ancient Gneiss Complex (3.43–3.66 Ga), which is extensively exposed in Eswatini and probably underlies the Paleoarchean terrains in the southern Kaapvaal Craton. The geotectonic setting was likely that of a submerged felsic crustal platform as enclaves within an oceanic plateau. [ABSTRACT FROM AUTHOR]

Valdivia Bank is an oceanic plateau in the South Atlantic formed by hot spot magmatism at the Mid‐Atlantic Ridge during the Late Cretaceous. It is part of the Walvis Ridge, an aseismic ridge and seamount chain widely considered to be formed by age‐progressive volcanism from the Tristan‐Gough plume. To better understand the formation and history of this edifice, we developed a bathymetric map of Valdivia Bank by merging available multibeam echosounder data sets with a bathymetry grid based mainly on satellite altimetry (SRTM15+). The bathymetric map reveals previously unresolved features including extensive rift grabens, volcanic mounds and knolls, and large‐scale sediment transport systems. After Valdivia Bank was emplaced and probably eroded at sea level, it underwent a period of rifting, followed by a secondary magmatic pulse that caused regional uplift to sea‐level, followed by subsidence to current depths. Shallow banks at depths of ∼1,000 m are the result of a thick sediment pile atop uplifted volcanic crust. Several shallower mounds (∼1,000–520 m) and a guyot (∼220 m) likely resulted from coral reef growth atop one or more volcanic pedestals formed during the younger Cenozoic magmatic event. As sediments accumulated on the shallow platforms, sediment transport systems developed as gullies, channels and mass transport deposits carved valleys and troughs, shedding sediment into abyssal fans at the plateau base. The new bathymetric map demonstrates that oceanic plateaus are geologically active long after initial emplacement. Plain Language Summary: Valdivia Bank is an oceanic plateau in the South Atlantic that was formed as part of Walvis Ridge by hot spot volcanism at the Mid‐Atlantic Ridge. Walvis Ridge topography is more complex than that of simple hot spot tracks. Moreover, younger‐than‐expected ages from dredge samples suggest a second phase of volcanism. To better understand the development of this plateau, we created a detailed bathymetry map by compiling available multibeam echosounder data with satellite‐altimetry‐based depth estimates. The map reveals previously unseen features including rifts, volcanic mounds, and submarine slides and sediment drainage features. These suggest that after Valdivia Bank formed, it underwent faulting, followed by volcanism that raised the plateau to sea level. Subsequently, the plateau subsided while accumulating a thick sediment cover. Shallow banks resulted from thick sediments atop the uplifted basement. Several shallower mounds likely resulted from coral reef growth atop a volcanic base formed during the later stage of volcanism. As sediments accumulated atop the plateau, they were shed through gullies, channels and submarine slides, carving valleys and troughs, and then deposited around the plateau base. Our findings demonstrate that oceanic plateaus can be geologically active long after their formation. Key Points: A bathymetry map was constructed for Valdivia Bank from multibeam data merged with satellite altimetry‐predicted depthsValdivia Bank experienced extension, forming rifts, and secondary volcanism, uplift, and exposure, then was capped by carbonate sedimentsValdivia Bank shows evidence of mass wasting, partly triggered by Cenozoic uplift and erosion, but also owing to sediment cap instability [ABSTRACT FROM AUTHOR]

Abstract Valdivia Bank is an oceanic plateau in the South Atlantic formed by hot spot magmatism at the Mid‐Atlantic Ridge during the Late Cretaceous. It is part of the Walvis Ridge, an aseismic ridge and seamount chain widely considered to be formed by age‐progressive volcanism from the Tristan‐Gough plume. To better understand the formation and history of this edifice, we developed a bathymetric map of Valdivia Bank by merging available multibeam echosounder data sets with a bathymetry grid based mainly on satellite altimetry (SRTM15+). The bathymetric map reveals previously unresolved features including extensive rift grabens, volcanic mounds and knolls, and large‐scale sediment transport systems. After Valdivia Bank was emplaced and probably eroded at sea level, it underwent a period of rifting, followed by a secondary magmatic pulse that caused regional uplift to sea‐level, followed by subsidence to current depths. Shallow banks at depths of ∼1,000 m are the result of a thick sediment pile atop uplifted volcanic crust. Several shallower mounds (∼1,000–520 m) and a guyot (∼220 m) likely resulted from coral reef growth atop one or more volcanic pedestals formed during the younger Cenozoic magmatic event. As sediments accumulated on the shallow platforms, sediment transport systems developed as gullies, channels and mass transport deposits carved valleys and troughs, shedding sediment into abyssal fans at the plateau base. The new bathymetric map demonstrates that oceanic plateaus are geologically active long after initial emplacement.

Mainland China has the most complex continental tectonics on Earth, making it one of the ideal laboratories for probing the tectonics and evolution of the Earth. However, no consensus has been reached regarding the basement tectonic architectures and evolution of mainland China. This paper focuses on the interpretation of aeromagnetic and seismic refraction data, closely incorporating available surface geological data, borehole data, and seismic data to trace the likely occurrences of oceanic plateau slices in the basement architecture of mainland China. We suggest that the highly positive aeromagnetic anomalies and thick high-velocity lower crustal layer indicate that the Junggar basin is floored by an oceanic plateau. The Tarim basin can be divided into a southeastern oceanic plateau block with strongly positive aeromagnetic anomalies and a northwestern passive continental margin block with weak aeromagnetic anomalies. Both blocks got amalgamated together during the late Paleoproterozoic, and the irregular, promiscuous aeromagnetic anomalies within the northwestern block are spatially consistent with and attributed genetically to the Tarim Large Igneous Province (LIP). The lower crust of the Qaidam basin is characterized by large P-wave velocity, suggesting that the basin is floored by an Early Paleozoic oceanic plateau, and the deep-seated subduction of the oceanic plateau could be responsible for the ultrahigh-pressure (UHP) metamorphism in the northern Qaidam margin during the Early Paleozoic. The western North China craton could be an assembly of multiple oceanic plateau fragments along irregular continental margins during the Paleoproterozoic. An intraplate suture (Miaowan suture) divides the Yangtze craton kernel to the east and the Shennong terrane to the west; both were amalgamated during the Neoproterozoic. The Yangtze craton kernel could be floored by an oceanic plateau basement characterized by large P-wave velocity and strongly positive aeromagnetic anomalies. All these oceanic plateau basements exhibit strong rigidity to resist later tectonic deformation and generally remain intact. • Junggar basin is floored by oceanic plateau of highly positive magnetic anomalies 3 and high velocity • Tarim basin is divided into northeastern oceanic plateau and southwestern passive 5 margin. • Qaidam basin is floored by oceanic plateau, whose subduction resulted in UHPM 7 in N. Qaidam margin • Western North China craton is an assembly of oceanic plateaus during the 9 Paleoproterozoic • Yangtze craton kernel is floored by oceanic plateau and divided by Miaowan suture 11 from Shennong terrane. [ABSTRACT FROM AUTHOR]

• For small-scale oceanic plateaus, the rifting manifests as a process from landward migration to seaward migration, accompanied by a transition from a symmetric to an asymmetric structure. • For large-scale oceanic plateaus, the rifting can form a symmetric structure during breakup. With larger initial lithospheric thinning, the crustal deformation distributes within a narrower region and forms the asymmetric structure. • The initial rifting migration dominates the Caroline Ridge deformation. A larger initial lithospheric thinning may exist beneath the small-scale section of Caroline Ridge during the Miocene rifting initiation. The dynamic rifting model of the Caroline Ridge, an oceanic plateau in the West Pacific, remains unclear. Previous studies have revealed that the crustal width of the Caroline Ridge clearly varies from the northwest to the southeast. Here, we investigate Caroline Ridge rifting using numerical simulation and reveal the relationships between different plateau sizes and rifting. For small-scale oceanic plateaus, the initial rift migration forms a symmetric structure. The strain transfers toward one side of the margin. The rifting manifests as a process from landward migration to seaward migration, accompanied by a transition from a symmetric to an asymmetric structure. With larger initial lithospheric thinning, larger ranges of crustal deformation appear with less basement tectonic subsidence. For large-scale oceanic plateaus, basement tectonic subsidence occurs within narrower ranges. The proximal half-graben structures rapidly abandon with relatively horizontal basement and small fault offsets on the rift flank, leading to a symmetric structure during breakup. With larger initial lithospheric thinning, crustal deformation occurs within a narrower region during the early stage. Landward rift migration dominates the deformation, resulting in an asymmetric structure. On the basis of these results, for the large-scale section of the Caroline Ridge, NW-trending normal faults originated from the landward rift migration. At present, seaward rift migration dominates the Caroline Ridge deformation, forming a relatively symmetric structure. For the small-scale section of the Caroline Ridge, the initial landward rift migration occurred. Larger initial lithospheric thinning may exist beneath the Caroline Ridge during the initiation of Miocene rifting. [ABSTRACT FROM AUTHOR]

[Display omitted] • Gaobaoyue adakitic magmatism was a result of oceanic plateau subduction. • Late Jurassic flat-slab subduction triggered abnormal tectonomagmatic activity. • Subduction of heterogeneous oceanic crust likely induced vertical slab tearing. • The eastern part of Southern Qiangtang Block has Cu–Au metallogenic potential. Oceanic plateau accretion and subsequent flat-slab subduction in modern convergent settings have profoundly influenced the nature of subduction and mantle dynamics. However, evaluating similar impacts in ancient convergent settings, where oceanic plateaus have been subducted but geological records are limited, remains challenging. In this study, we present geochronological and geochemical data for a suite of ore-associated plutonic rocks from the Gaobaoyue area of northern Tibet. These rocks have zircon U–Pb ages of 152–146 Ma, with high Sr contents and Sr/Y and La/Yb ratios, low MgO, Yb, and Y contents, and depleted Sr–Nd–Hf isotopic compositions, consistent with an adakitic affinity that was generated by the partial melting of subducting oceanic crust. We compare the Late Jurassic adakitic magmatism with the spatiotemporal evolution of magmatism in northern Tibet to infer oceanic plateau subduction and subsequent flat-slab subduction in the Bangong–Nujiang Tethyan Ocean. This tectonic model explains (i) slab-derived adakitic magmatism, (ii) the observed lull in magmatic activity, (iii) intraplate compression and uplift, and (iv) subduction jump and initiation. We also propose that the subduction of heterogeneous oceanic crust (i.e., buoyant oceanic plateau subduction) provided favorable conditions for tectonic exhumation, vertical slab tearing, and the formation of Cu–Au deposits. Our findings not only have implications for establishing the fundamental process of oceanic plateau accretion in ancient subduction zones but also provide an alternative explanation for Late Jurassic complex tectonomagmatic activity in northern Tibet. [ABSTRACT FROM AUTHOR]

The Caribbean plate is an enclosed oceanic basin whose formation and evolution are controversial. In the most commonly accepted model, the Caribbean plate is mainly composed of the Caribbean Large Igneous Province (CLIP) and the buoyant characteristic of this oceanic plateau resisted subduction and allowed an eastward migration to its present position north of South America. In this study, we integrate a broad range of geophysical and geomorphological data to define structural elements and present‐day tectonics of the Caribbean plate and the surrounding region. We present a Bouguer gravity anomaly map and a new crustal thickness map that documents large areas of normal‐thickness oceanic crust within the Venezuela and Colombia basins of the Caribbean plate. Selected cross sections of seismicity and P‐wave anomalies from a seismic tomographic model depict the present‐day geometry of subducting oceanic plates within the Caribbean region. We observe that rather than resisting subduction, as expected for the thick crust of a buoyant large igneous province, the subduction of the Caribbean plate can be traced to a depth of 600 km beneath NW South America. This, together with the crustal thickness map, implies that a significant area of the Caribbean plate, including the subducted portion, is composed of normal‐thickness oceanic crust. As proposed by the Pacific origin model, the Caribbean plate likely migrated eastward from the Pacific Ocean as an oceanic plate mostly with normal‐thickness crust and limited portions of the crust thickened by hot spot volcanism (CLIP). Plain Language Summary: The Caribbean plate and northern South America are studied using topography and multiple geophysical data sets, including gravity, magnetics, crustal thickness, seismicity, and seismic images of the upper mantle. These data sets were used to analyze crustal properties as well as the past and present interaction of tectonic plates in this region. Our results show large areas of ocean crust with normal thickness within the Caribbean plate. Seismicity in the circum‐Caribbean subduction zones rarely exceeds 200 km in depth, whereas seismic imaging shows subducting slabs reach a depth of 600 km or more. This implies that subduction has been long‐lived at these active margins. These results also show that the Caribbean plate is subducting beneath NW South America, something that would not be expected for the thick crust of a buoyant large igneous province. As proposed by the Pacific origin model, the Caribbean plate migrated eastward from the Pacific Ocean as an oceanic plate mostly with normal‐thickness crust and limited portions of the crust thickened by hot spot volcanism. Key Points: A new crustal thickness map and gravity maps reveal large areas of normal‐thickness oceanic crust within the Caribbean plateP‐wave seismic tomography images show that the subducted Caribbean plate reaches 660 km depth, but slab seismicity terminates at 200 kmCombined seismicity, gravity, and magnetic maps reveal the active tectonics of the circum‐Caribbean accretionary and magmatic boundary [ABSTRACT FROM AUTHOR]

Abstract The Caribbean plate is an enclosed oceanic basin whose formation and evolution are controversial. In the most commonly accepted model, the Caribbean plate is mainly composed of the Caribbean Large Igneous Province (CLIP) and the buoyant characteristic of this oceanic plateau resisted subduction and allowed an eastward migration to its present position north of South America. In this study, we integrate a broad range of geophysical and geomorphological data to define structural elements and present‐day tectonics of the Caribbean plate and the surrounding region. We present a Bouguer gravity anomaly map and a new crustal thickness map that documents large areas of normal‐thickness oceanic crust within the Venezuela and Colombia basins of the Caribbean plate. Selected cross sections of seismicity and P‐wave anomalies from a seismic tomographic model depict the present‐day geometry of subducting oceanic plates within the Caribbean region. We observe that rather than resisting subduction, as expected for the thick crust of a buoyant large igneous province, the subduction of the Caribbean plate can be traced to a depth of 600 km beneath NW South America. This, together with the crustal thickness map, implies that a significant area of the Caribbean plate, including the subducted portion, is composed of normal‐thickness oceanic crust. As proposed by the Pacific origin model, the Caribbean plate likely migrated eastward from the Pacific Ocean as an oceanic plate mostly with normal‐thickness crust and limited portions of the crust thickened by hot spot volcanism (CLIP).

An oceanic plateau, the Yakutat terrane, has entered the subduction system across southcentral Alaska. Its down‐dip fate and relationship to overlying volcanism is still debated. Broadband seismometers from the Wrangell Volcanism and Lithospheric Fate (WVLF) temporary experiment were deployed with <20 km spacing across southcentral Alaska to study this region. An array‐based deconvolution procedure is used to isolate the scattered P and S coda of teleseismic P waves for imaging discontinuity structure. This procedure is applied to WVLF and other dense seismic arrays across southcentral Alaska in a manner that accounts for near‐surface wavespeed variations. Two imaging techniques are employed: two‐dimensional migration and three‐dimensional common‐conversion‐point (CCP) stacking. Migrating the scattered phases along WVLF stations shows the ∼18 ± 4 km thick Yakutat crust subducting beneath the Wrangell Volcanic field to the NNE. It is offset from the Alaska‐Aleutian seismic zone laterally by 250 km to the southeast at 100 km depth, and dips more steeply (45°). At depths <45 km, CCP stacking reveals that the Yakutat crust is continuous for over 450 km along strike. This shallow continuity and deeper offset suggest a tear in the subducting Yakutat slab at depths >45 km, around 146°W. CCP stacking also reveals a continuous thin low‐velocity layer atop the underthrust Yakutat crust for >450 km along strike, at all depths <35 km. The uniform low‐velocity thrust zone indicates consistent properties through multiple rupture‐zone segments, showing that low‐velocity channels generally correspond with subduction megathrusts. Plain Language Summary: Typical oceanic crust that descends in subduction zones is 6–7 km thick. The subducting crust across southcentral Alaska is an >11 km thick oceanic plateau known as the Yakutat terrane. The western side of this study region has no subduction volcanism; the eastern side is home to the Wrangell Volcanic Field (WVF), one of the most voluminous continental volcanic fields in the world. Multiple seismometer arrays are used to image subsurface discontinuity structure associated with the subduction of the Yakutat terrane. We image the boundaries of the subducting Yakutat crust, and the base of the continental crust where it does not interfere with the subducting crust. The Yakutat terrane is a continuous feature for >450 km along strike at depths <45 km, but deeper it appears to be separated into two segments with >250 km of lateral offset, a 45° difference in orientation, and a 20° difference in dip angle. These differences provide strong evidence for a tear in the subducting plate that may be the cause of the extensive WVF. The results also show low seismic velocities atop the subducted Yakutat terrane at depths <35 km, which could be sediment being dragged down along the plate interface. Key Points: Yakutat oceanic plateau is subducting beneath Wrangell Volcanic Field (WVF) to at least 110‐km depthA thin low‐velocity layer delineates the megathrust atop the subducting Yakutat crust for over 450 km along‐strike, at depths <35 kmA tear in the subducting Yakutat terrane lies 100–200 km west/northwest of the WVF [ABSTRACT FROM AUTHOR]

This study focuses on the mafic–ultramafic lavas of the Early Carboniferous outcrop in Mangxin, southwestern Yunnan, China. Picrites with 26–32 wt% MgO and a quenched texture are the most significant components of this rock association. This article divides the Mangxin picrites into two types. The mantle potential temperature ($T_{{p}}$) of these picrites is higher than the $T_{{p}}$ range of mid-ocean ridges and reaches that of mantle plumes. According to the geochemical characteristics, the Type-1 picrites probably formed from the melting of the mantle plume head and were contaminated by ambient depleted mantle, whereas the Type-2 picrites formed from the melting of mantle plume tails. These plume-related mafic–ultramafic rocks in Mangxin and the ocean island basalt (OIB)-carbonate rock associations in many areas of the Changning–Menglian belt provide significant evidence for the improvement of previous models of the Palaeotethyan oceanic plateau.

The morphostructural characteristics of the main taxa of southern Indian Ocean, such as the Del Cano-Crozet, Conrad, and Kerguelen plateaus, are given based on structural-tectonic analysis. A depth map of the acoustic basement of the eastern part of the Afro-Antarctic megadepression is first built using the digitized NGDS database on the thickness of the sedimentary cover of the Indian Ocean, which is available on the Internet. A critical analysis of deep seismic sounding (DSS) data on the Kerguelen plateu hs been performed. A geochemical analysis of more than 100 samples of basalts, acidic rocks, and rocks of sedimentary origin, collected on the islands of the Kerguelen archipelago and raised by dredging and deep-sea drilling from the Kerguelen and Conrad plateaus, is carried out. The study has shown that the plateaus resemble the Madagascar Ridge in terms of morphostructure and a number of other features. It is concluded that these flat-topped horst massifs were the part of the "structural bridge" that connected Madagascar and the eastern part of mainland Antarctica no later than the Paleogene. A proposed alternative version of the geological interpretation of the deep seismic data states that the plateau has a relatively homogeneous structure along the strike, including a thick (at least 15-km) layer of continental crust. An analysis of the depth map of the acoustic basement made it possible to identify the depocenters of the relatively isolated Enderby, Shackleton and Labuan basins framing the Kerguelen Plateau on the southern side. The paragenetic connections of the Kerguelen Plateau with the basins indicate that the isolation of the Kerguelen Plateau from East Antarctica and the formation of the modern structure of the region began in the Late Cretaceous and ended with the last phase of tectonic activation in the Late Miocene–Pliocene. The results of geochemical analysis show that the geochemical and petrological anomalies of the plateau and islands are associated with the crust, and not with the mantle contamination, as well as with the continental nature of the Kerguelen Plateau. [ABSTRACT FROM AUTHOR]

Oceanic plateau crust is thicker and hotter than the surrounding "normal" oceanic crust, causing differential subsidence and subsequent strain between the two domains. Here, we show that recently active sedimentary faults that have been imaged adjacent to the Rio Grande Rise, an oceanic plateau in the western South Atlantic, have extensions that can penetrate at least ∼1.5 km into the upper oceanic crust. Our high‐resolution seismic velocity model indicates that these fault zones significantly reduce seismic velocities and increase inferred porosity and permeability. We also present physical property‐constrained fluid flow models that predict substantially increased fluxes along these pathways compared to crust not affected by faulting. As these phenomena are effectively enabled by the proximity of an oceanic plateau, we suggest that similar geologic settings globally may also exhibit elevated levels of tectonic and hydrothermal activity, with implications for the hydration of mature oceanic crust and the oceanic crustal biosphere. Plain Language Summary: Oceanic crust slowly sinks as it cools after its formation at midocean spreading centers, but it does so more slowly than usual at oceanic plateaus, where anomalous magmatism has left it relatively thick and buoyant. The different rates of sinking can induce faults that rupture the transitionary crust between the plateau and the surrounding oceanic crust. The Rio Grande Rise, located in the western South Atlantic Ocean, is an oceanic plateau at whose fringes recently active faults have been imaged in the sediments that cover the crust. We trace those faults at least 1.5 km deep into the crust and provide additional evidence for recent fault activity. We also show that fluids likely flow along those pathways, spilling into the ocean in much larger volumes than in normal oceanic crust. Faulting and associated fluid flow is likely also very active in crust bordering other oceanic plateaus globally, affecting the composition of the crust and the habitat of living organisms. We estimate the affected area to make up close to 10% of all oceanic crust on Earth. Key Points: Recently, active extensional faults adjacent to the Rio Grande Rise penetrate at least ∼1.5 km into the crustThe imaged faults significantly increase fluid circulation within the upper crust and fluid exchange with the oceanCrust adjacent to oceanic plateaus and other major bathymetric features may release an estimated 43 km3 of fluid into the oceans globally [ABSTRACT FROM AUTHOR]

Oceanic plateaus are characterized by overthickened crust and rheologically strong and chemically depleted mantle root with respect to normal oceanic lithosphere. The buoyant nature makes them have a great potential to resist subduction and initiate a new subduction zone behind the plateaus, yet the geodynamic process remains enigmatic. Here, we use 2D thermo‐mechanical modeling method to investigate the role of an oceanic plateau in subduction zone reorganization. We systematically examine the rheological strength and compositional density of oceanic plateau mantle and the size of oceanic plateau. Three distinct subduction styles are observed: (a) steep subduction without subduction zone reorganization, favored by a small‐sized (≤150 km) or lowly depleted oceanic plateau; (b) breakoff of subducting slab followed by flat‐slab subduction, which is conditional on a moderate‐sized (≥300 km) oceanic plateau with high degree depletion but relatively low strength; and (c) initiation of a new subduction zone behind the plateau (subduction zone jump), facilitated by a moderate‐sized oceanic plateau with a strongly depleted mantle root. The geodynamic results demonstrate that the overriding lithosphere undergoes a tectonic force switch from compression to tension in ∼5 Myr as the subduction zone is reorganized. This can be reflected in the crustal deformation of the overriding plate and used as an indicator to identify past subduction zone jumps. The spatial relationship predicted by the subduction zone jump models explains the Jurassic closure event of the accretion on southern Qiangtang at ∼175 Ma and the intraoceanic infant arc magmatism in the Meso‐Tethys at ∼165 Ma. Key Points: Different subduction styles controlled by the buoyancy and strength of the oceanic plateau, as well as its sizeSubduction zone jump occurs when the plateau has a strong rheological and highly depleted mantle rootThe continental tectonic force transformation systems can be used as an indicator to identify ancient subduction zone jumps [ABSTRACT FROM AUTHOR]

As one of the largest Phanerozoic orogens in the world, the Central Asian Orogenic Belt ( CAOB) is an excellent place for studying accretionary orogenic process and continental crust growth. It is widely accepted that the CAOB formed by long-lived evolution of the Paleo-Asian Ocean (PAO) from Neoproterozoic to Early Mesozoic, comprises various allochthonous fragments, such as micro continents, island arcs, seamounts/ oceanic plateaus, accretionary prisms, and ophiolitic melanges. The composition of ophiolitic melange is almost same in the western CAOB. Except the typical ophiolite components, the ophiolitic melanges contain pillow basalt, volcanic breccia, reef limestone, olistostrome, and terrestrial elastic rocks. Geochemically, the mafic rocks in ophiolitic melange can be divided into two groups of MORBand OIB-type. The MORB-type belongs to tholeiitic basalt series and shows subduction characteristics; the OIB-type belongs to alkaline basalt series, and is formed in seamount/ oceanic plateau affinity. The age, property and distribution of ophiolitic melanges and metamorphic rocks in the western CAOB indicate that the subduction initiation time of the PAO is no later than Early Neoproterozoic, and the locat ion should be on the southern margin of Siberia plate and gradually develop southward. In the early development of the PAO, the mechanism of subduction initiation should be mantle plume-induced dominant. However, in the later period, the seamount/ oceanic plateau may block the subduction channel, causing the subduction polarity reversal and transition, and the subduction initiation occurs. Initiation of new subduction zone is a difficult problem of Earth's plate tectonics regime. The reason is that the subduction initiation is an extremely short process, scarcity of geological record, and there are few cases of subduction initiation that are happening on Earth today. Therefore, it is necessary for geologists to work together to reveal the past and present lives of the PAO, and to solve the mystery of the subduction initiation of plate tectonics. [ABSTRACT FROM AUTHOR]

The Bangong‐Nujiang Suture Zone (BNSZ) in central Tibet represents relics of the Meso‐Tethys Ocean that once separated the Lhasa and Qiangtang terranes. When and how this ocean closed has been a matter of debate, and the cause of the uncertainty stems primarily from a lack of consensus as to whether Early Cretaceous ophiolite exists within the BNSZ. New geochronological and geochemical data presented here identify ∼138–134 Ma MORB‐like and OIB‐type mafic rocks in the Kangqiong area of the western BNSZ. These data, together with the spatially associated peridotite and marine sediment, provide the first firm evidence for the presence of Early Cretaceous ophiolite within the BNSZ. Our integrated study of geological, mineralogical, and geochemical data suggests that the Kangqiong Ophiolite formed in a forearc setting related to the subduction re‐initiation of the Meso‐Tethys Ocean. By combining the present results with a synthesis of tectonomagmatism in central Tibet, including the existence of an Early Jurassic oceanic plateau within the Meso‐Tethys Ocean, the magmatic lull (∼145–130 Ma) in the Qiangtang Terrane, an angular unconformity between Lower Jurassic oceanic rocks and Upper Jurassic shallow‐marine strata, and the compositional differences and migration of magmatism before and after the magmatic lull, we propose a new model of the evolution of the Meso‐Tethys Ocean. This model proposes that the collision of an oceanic plateau with the Qiangtang continental margin caused the termination of Meso‐Tethyan subduction during the Late Jurassic and subsequent re‐initiation behind the oceanic plateau during the Early Cretaceous. Key Points: First evidence for the presence of Early Cretaceous ophiolite within the Bangong‐Nujiang Suture Zone, central TibetThe Kangqiong Ophiolite formed in a fore‐arc setting that was synchronous with a magmatic lull following a collisional eventSubduction termination and re‐initiation of Meso‐Tethys Ocean caused by collision of an oceanic plateau with Qiangtang continental margin [ABSTRACT FROM AUTHOR]

Shatsky Rise oceanic plateau was emplaced during a period of frequent geomagnetic polarity reversals, allowing reconstruction of its tectonic evolution using magnetic anomalies. Prior studies mainly focused on identifying magnetic isochrons and encountered difficulties in tracing magnetic lineations over high relief. We complied a large magnetic data set over Shatsky Rise and its environs, using 5.5 × 106 data points from 96 geophysical cruises spanning 54 years. The long‐time span and heterogeneity of component data sets made data merger a challenge. Contributions of internal and external fields, and spurious readings were removed during processing. A "backbone" method, using recent GPS‐navigated data as a foundation, was developed to improve the coherency of the data set. The singular characteristic of the new magnetic anomaly map is that linear magnetic anomalies are ubiquitous. In nearly every place where data are dense enough to delineate anomaly trends, the plateau and surrounding crust are characterized by linear anomalies. Discordant anomalies in some areas imply complex tectonics related to triple junction migration and ridge reorientation. Tamu Massif apparently formed along a segment of Pacific‐Farallon spreading ridge that rotated by 90° as a triple junction migrated through the edifice. Ori Massif appears to have formed on the Pacific‐Izanagi ridge between triple junctions. Shirshov Massif contains discordant lineations that may indicate a microplate. The pervasive occurrence of linear magnetic anomalies within Shatsky Rise implies that these volcanic edifices must have formed by spreading analogous to mid‐ocean ridges that formed anomalously thick crust. Key Points: A large and heterogeneous marine magnetic data set has been compiled to construct a new magnetic anomaly map for Shatsky RiseGPS‐navigated data were used as a "backbone" reference frame for older data to correct navigational errors and improve data agreementAll of Shatsky Rise is traversed by linear/curvilinear magnetic anomalies, indicating its formation by enhanced ridge volcanism [ABSTRACT FROM AUTHOR]

The Mikabu Unit (Mikabu greenstones) was an oceanic plateau that was in the Mesozoic Paleo-Pacific Ocean. Large-igneous-province (LIP) activity has been proposed as the origin of the oceanic plateau of the Mikabu Unit. This study aims to reveal LIP activity in the Paleo-Pacific Ocean. We present geochemical and geochronological data for the Mikabu Unit and the Middle Jurassic to Early Cretaceous Chichibu accretionary complex (i.e., the Kashiwagi and Kamiyoshida units), both of which underwent the same high-pressure low-temperature metamorphism as the Mikabu Unit, in the Kanto Mountains, central Japan. The Mikabu Unit contains oceanic plateau basalts characterized by incompatible element depletion and high chondrite normalized Gd/Yb ratios. These basalts are interpreted to have erupted in the age of 157.0 ± 0.9 Ma (Late Jurassic), based on zircon U–Pb dating of anorthosite. The basalt geochemistry indicates that oceanic plateau basalts occur in the Kashiwagi Unit. Although basalts in the Mikabu Unit were thought to have formed at the Pacific–Izanagi–Farallon triple junction in the previous studies, we propose they formed on older oceanic crust of the Izanagi Plate during the Late Jurassic, which was located several thousand kilometers from the triple junction. The Kashiwagi and Mikabu units were accreted to Asia during the Early Cretaceous. Unlabelled Image • The Mikabu Unit includes oceanic plateau basalts formed by LIP activity • The basalts of the Mikabu Unit were erupted at 157 Ma • The basalts formed far from Izanagi–Pacific boundary [ABSTRACT FROM AUTHOR]

Of the world's oceans, the Pacific has the most abundant distribution of seamount trails, oceanic plateaus and hot spots, and has the longest fracture zones. However, little is known of their thermal structures due to difficulties of heat flow measurement and interpretation, and in inferring thermal anomalies from low-resolution seismic velocities. Using recently published global magnetic models, we present the first independent constraint on Pacific geothermal state and mantle dynamics, by applying a fractal magnetization inversion model to magnetic anomaly data. Warm thermal anomalies are inferred for all known active hot spots, most seamount trails, some major fracture zones, and oceanic lithosphere between ~100 and ~140 Ma in age. While most Curie points are among the shallowest in the zone roughly bounded by the 20 Ma isochrons, abnormally deep Curie points are found along nearly all ridge crests in the Pacific, related to patchy, long-wavelength and large-amplitude magnetic anomalies that are most likely caused by prevailing magmatic or hydrothermal processes. Many large contrasts in the thermal evolution between the Pacific and North Atlantic support much stronger hydrothermal circulation occurring in Pacific lithospheres younger than ~60 Ma, which may have disguised from surface heat flow any deep thermal signatures of volcanic structures. Yet, at depths of the Curie points, our model argues for warmer Pacific lithosphere for crustal ages older than ~15 Ma, given a slightly higher spatial correlation of magnetization in the Pacific than in the North Atlantic.

The syenitic rocks of South Rallier du Baty Intrusive Complex (SRBIC) represent intrusions into the oceanic plateau basalts of the south‐western Kerguelen Islands. The SRBIC was previously interpreted as a typical ring complex due to magma emplacement with cauldron subsidence. Our new structural and geochronological data reveal that it is a laccolith built between 11.6 and 7.9 Ma by successive injections of magma sheets around the crust–mantle boundary, with an average injection rate between 0.8 and 1.4 × 10−4 km3/year. These results establish strong similarities between the SRBIC, the only recorded example of a felsic laccolith in an oceanic intraplate setting, and many continental plutons emplaced in various geodynamic setting. The SRBIC thus has the characteristics of a continental plutonic complex emplaced in an oceanic plateau crust. We postulate the critical parameter relevant to causing such similarities and plutonic magmatism is crustal thickness. [ABSTRACT FROM AUTHOR]

Modern oceans contain large bathymetric highs (spreading oceanic ridges, aseismic ridges or oceanic plateaus and inactive arc ridges) that, in total, constitute more than 20–30% of the total area of the world's ocean floor. These bathymetric highs may be subducted, and such processes are commonly referred to as ridge subduction. Such ridge subduction events are not only very common and important geodynamic processes in modern oceanic plate tectonics, they also play an important role in the generation of arc magmatism, material recycling, the growth and evolution of continental crust, the deformation and modification of the overlying plates, and metallogenesis at convergent plate boundaries. Therefore, these events have attracted widespread attention. The perpendicular or high-angle subduction of mid-ocean spreading ridges is commonly characterized by the occurrence of a slab window, and the formation of a distinctive adakite-high-Mg andesite-Nb-enriched basalt-oceanic island basalt (OIB) or a mid-oceanic ridge basalt (MORB)-type rock suite, and is closely associated with Au mineralization. Aseismic ridges or oceanic plateaus are traditionally considered to be difficult to subduct, to typically collide with arcs or continents or to induce flat subduction (low angle of less than 10°) due to the thickness of their underlying normal oceanic crust (>6–7 km) and high topography. However, the subduction of aseismic ridges and oceanic plateaus occurred on both the western and eastern sides of the Pacific Ocean during the Cenozoic. On the eastern side of the Pacific Ocean, aseismic ridges or oceanic plateaus are being subducted flatly or at low angles beneath South and Central American continents, which may cause a magmatic gap. But slab melting can occur and adakites, or an adakite-high-Mg andesite-adakitic andesite-Nb-enriched basalt suite may be formed during the slab rollback or tearing. Cu-Au mineralization is commonly associated with such flat subduction events. On the western side of the Pacific Ocean, however, aseismic ridges and oceanic plateaus are subducted at relatively high angles (>30°). These subduction processes can generate large scale eruptions of basalts, basaltic andesites and andesites, which may be derived from fractional crystallization of magmas originating from the subduction zone fluid-metasomatized mantle wedge. In addition, some inactive arc ridges are subducted beneath Southwest Japan, and these subduction processes are commonly associated with the production of basalts, high-Mg andesites and adakites and Au mineralization. Besides magmatism and Cu-Au mineralization, ridge subduction may also trigger subduction erosion in subduction zones. Future frontiers of research will include characterizing the spatial and temporal patterns of ridge subduction events, clarifying the associated geodynamic mechanisms, quantifying subduction zone material recycling, establishing the associated deep crustal and mantle events that generate or influence magmatism and Cu-Au mineralization, establishing criteria to recognize pre-Cenozoic ridge subduction, the onset of modern-style plate tectonics and the growth mechanisms for Archean continental crust. [ABSTRACT FROM AUTHOR]

This study focuses on the mafic--ultramafic lavas of the Early Carboniferous outcrop in Mangxin, southwestern Yunnan, China. Picrites with 26-32 wt% MgO and a quenched texture are the most significant components of this rock association. This article divides the Mangxin picrites into two types. The mantle potential temperature (Tp) of these picrites is higher than the Tp range of mid-ocean ridges and reaches that of mantle plumes. According to the geochemical characteristics, the Type-1 picrites probably formed from the melting of the mantle plume head and were contaminated by ambient depleted mantle, whereas the Type-2 picrites formed from themelting of mantle plume tails. These plume-related mafic--ultramafic rocks in Mangxin and the ocean island basalt (OIB)-carbonate rock associations in many areas of the Changning--Menglian belt provide significant evidence for the improvement of previous models of the Palaeotethyan oceanic plateau. [ABSTRACT FROM AUTHOR]

Subduction of oceanic plateaux are events that have occurred infrequently in Earth's history. Although rare, these events are thought to considerably influence regional tectonics and global plate motions. In the mid‐Cretaceous the oceanic Hikurangi Plateau collided with the formerly active East Gondwana margin: An event which falls into the same of a sudden change from subduction to extensional processes, including graben formation, development rift basin development, and exhumation of metamorphic core complexes in the Zealandia continent as well as a global‐scale plate reorganization event. In this study, we use recently acquired seismic refraction and gravity data along one profile across the submarine Chatham Rise, which represent a former accretionary wedge of the East Gondwana subduction zone. We demonstrate that the southward extent of the subducted Hikurangi Plateau in the lower crust beneath the submarine Chatham Rise along our profile is only ~150. This is ~150 km less than the previously suggested extent. Furthermore, we interpret that a slice of the subducted Phoenix Plate remains attached to the southern edge of the Hikurangi Plateau. We suggest that cessation of subduction in response to the Hikurangi Plateau jamming as well as the rollback and detachment of the Phoenix Plate slab played an important role in the changing tectonic forces across Zealandia in mid‐Cretaceous. Moreover, we suggest that the subduction cessation along the Hikurangi Plateau segment led to the fragmentation of the Gondwana subduction zone and Phoenix Plate, which significantly influenced and potentially prolonged the global mid‐Cretaceous plate reorganization event. Key Points: P‐wave velocity and gravity models reveal the extent of the Hikurangi Plateau and Phoenix Plate beneath the submarine Chatham RiseFlattening, rollback, and detachment of the Phoenix Plate slab led to widespread extension in southern ZealandiaSubduction cessation and fragmentation of the Phoenix Plate triggered a global plate reorganization event at 105 Ma [ABSTRACT FROM AUTHOR]

Oceanic plateaus are a significant type of large igneous provinces in the oceans, providing insights to regional tectonic events and mantle behavior. The three world's largest oceanic plateaus, the Ontong Java Plateau, the Kerguelen Plateau and the Shatsky Rise, are representatives in displaying extraordinary fluxes of magma from mantle to lithosphere. Detailed description incorporating transdisciplinary observations on marine geology, geophysics and geochemistry allow us to test the two lively-debated oceanic plateau formation hypotheses (mantle plume and plate boundary models). Predictions from either hypothesis merely obtain partial support. It is therefore unclear to differentiate one model from another one regarding the oceanic plateau formation. Careful comparisons of the three oceanic plateaus show many commonalities and even more differences in their formation and evolution. This diversity signifies one may not be typical of all. Notably, several key common features, i.e., massive and rapid eruption and near-ridge formation setting, imply that the lithospheric volcanic emplacement of oceanic plateaus was controlled by seafloor spreading despite a mantle plume exists peripherally. If a coincidence of mantle plume and spreading ridge occurs, it may indicate a plume-ridge interaction. One possible mechanism is that spreading ridge is dragged by a plume and migrates to the location of the plume. Another possibility is that the asthenosphere is fed by a plume nearby and generates melting anomalies along the spreading ridge. [ABSTRACT FROM AUTHOR]

The Meso-Tethyan oceanic plateaus are becoming conspicuous as giant units on the oceanic floor and have played important roles in both continental marginal orogenesis and Tethys oceanic evolution. In this study, we present mineralogical, geochronological, geochemical and Sm–Nd isotopic data for basaltic lavas from the Namco ophiolite and a high-Mg pillow lava–dyke–gabbro association from the Pengco ophiolite in central Tibet. Zircon U–Pb and Ar–Ar dating reveals that the Namco lavas erupted at ∼181 Ma while the Pengco boninitic association formed at ∼164 Ma. The Namco lavas display nearly flat rare-earth element (REE) patterns with no Nb–Ta depletions as well as high ε Nd values, characteristic of oceanic plateau lava. In contrast, the Pengco high-Mg rocks exhibit low REE concentrations below the normal mid-ocean ridge basalt (N-MORB), ubiquitous Nb–Ta depletions and low ε Nd values, and the dykes and gabbros are characterized by U-shape REE patterns, indicating that they could have derived from a depleted mantle source that was contaminated by sedimentary flux and marking a mid-Jurassic initial intra-oceanic arc magmatism erupted on the Early Jurassic Meso-Tethyan oceanic plateau represented by the Namco ophiolite. Our Pengco boninitic rocks, along with the literature data, indicate a 167–160 Ma boninitic-like initial intra-oceanic arc within the Bangong Meso-Tethys, running from the Shiquanhe area to the Naqu area with a length of ∼1000 km, which was uniformly built on the Early Jurassic Meso-Tethyan oceanic plateau. Our literature investigation also indicates a ∼175 Ma accretionary orogeny with distinct signature of the oceanic plateau involvements along the southern Qiangtang continental margin, which is manifested by regional metamorphic, magmatic and depositional records. We thus suggest that the accretion of the Early Jurassic Meso-Tethyan oceanic plateau onto the southern Qiangtang continental margin resulted in the extensive orogeny along the continental margin, jammed the subduction zone at ∼175 Ma and induced intra-oceanic subduction initiation as well as the intra-oceanic infant arc magmatism in the Meso-Tethys at ∼164 Ma. Image 1 • The Pengco high-Mg magmatic association in central Tibet was dated at ∼164 Ma. • They derived from a depleted mantle source contaminated by sedimentary flux. • They represent nascent intra-oceanic arc magmatism. • A mid-Jurassic infant intra-oceanic arc existed within the Bangong Meso-Tethys. • The arc could be induced by accretion of Early Jurassic oceanic plateau at ∼175 Ma. [ABSTRACT FROM AUTHOR]

The generation of erosive and accretionary margins has yet to be determined. Here, we explore the variations in the forearc structures of the New Guinea Trench (NGT) based on the latest high-quality multichannel seismic profiles perpendicular or subparallel to the New Guinea Trench axis. Our results reveal that for the domain of the oceanic crust subducted beneath the NGT (O-NGT), the thickness of the sedimentary strata decreases from the forearc sedimentary basin to the forearc slope. The basement is generally characterized by homogeneous intra-basement reflections, and few discontinuous, prominent layered reflections in the basement are identified. On the forearc slope, arcward-dipping fault-plane reflections have been identified within the basement, and an abrupt topographic decrease occurs in the eastern part of the forearc basement uplift. Widespread sedimentary sequences are identified as the present, transparent and horizontal seismic reflections with high continuities and low amplitudes. The sedimentary sequences show a large lateral variation of thickness and present folded features near the seaward-dipping faults due to the development of slump bodies. However, the sedimentary sequences in the forearc slope of the domain of the oceanic plateau subducted beneath the NGT (P-NGT) are obviously thicker than those of the O-NGT and present folded features. The stratigraphic thickness from the forearc sedimentary basin to the forearc slope clearly increases. Our initial results initially indicate that the NGT might constitute an internal reverse polarity subduction zone that changes from an erosive margin in the O-NGT to an accretionary margin in the P-NGT. • The domain of the oceanic crust subducted beneath the NGT (O-NGT) shows erosive margin features. • The domain of the oceanic plateau subducted beneath the NGT (P-NGT) shows accretionary margin features. • NGT constitutes an internal reverse polarity subduction zone that changes from an erosive margin to an accretionary margin. [ABSTRACT FROM AUTHOR]

Oceanic plateaus are large igneous provinces in the oceans, created by massive underwater eruptions, but their late-stage volcanism is poorly understood. With the addition of recent high-quality bathymetric data to existing data, 286 secondary cones were discovered over Shatsky Rise oceanic plateau. These cones with steeper flank slopes (mean 6.1° ± 4.4°) and smaller sizes (102–1923 m in height) are morphologically distinct from the plateau, and they are thought to have formed after the main volcanic episodes. Cone height and characteristic height (420 m) are close to seamounts in the Pacific Ocean, whereas greater than those in the Atlantic Ocean. Mean flatness of Shatsky Rise's cones (0.25 ± 0.20) are similar to that of seamounts in both Pacific and Atlantic Oceans, but notably density in cone distribution (0.56 km−3) and their mean slope are significantly lower than those of seamounts in the two oceans. Lower slopes of secondary cones within Shatsky Rise may be explained by higher effusion rates of remaining magma. Although cone formation was expected to have a link to rifting by seafloor spreading, weak relationship between cone orientation and magnetic anomaly pattern implies that the expectation is negative. Moreover, weak correlation between the cone height and depth indicates it is not true that volcanic cones grow taller when they occur closer to the massif summits with thicker oceanic crust, which was suggested as the increase in hydraulic pressure. Cone height and flatness are also not strongly related, implying that remaining magma supply was too limited to foster the cones to critical height. [ABSTRACT FROM AUTHOR]

This study focuses on the mafic-ultramafic lavas of the Early Carboniferous outcrop in Mangxin, southwestern Yunnan, China. Picrites with 26–32 wt% MgO and a quenched texture are the most significant components of this rock association. This article divides the Mangxin picrites into two types. The mantle potential temperature (T p) of these picrites is higher than the T p range of mid-ocean ridges and reaches that of mantle plumes. According to their geochemical characteristics, type-1 picrites probably formed from the melting of the mantle plume head and were contaminated by the ambient depleted mantle, whereas type-2 picrites formed from the melting of mantle plume tails. These plume-related mafic-ultramafic rocks in Mangxin and the ocean island basalt (OIB)-carbonate rock associations in many areas of the Changning–Menglian belt provide significant evidence for the improvement of previous models of the Palaeotethyan oceanic plateau. [ABSTRACT FROM AUTHOR]

Abstract Seismically detectable discontinuities at mid-depths of some cratonic lithospheric mantle define mid-lithosphere discontinuities (MLD), demonstrating that the lithospheric mantle is layered. The genesis and strength of the MLD are still in debate, most proposed models suggest the MLD is likely not weaker than the normal lithosphere, whereas other proposed models suggest that some metasomatised MLD rocks are weaker than the normal lithospheric mantle rocks. Thus, the weak MLD is likely a weakly-coupled layer at mid-depths in some cratonic lithosphere blocks, possibly influencing their stabilities. We assess the geodynamic significance of the MLD using geodynamic modeling. We propose that a weak MLD, with lower effective viscosity, can be connected to thinned cratonic margins during the evolution of some cratons and form continuously connected weak zones from cratonic margins to craton interiors, which can lead to lithospheric thinning or removal by extension, basal drag, delamination, thermochemical erosion, and other actions. Through analyzing different scenarios, we propose that some samples of weak MLDs can be found in a composite ophiolite profile formed on the Precambrian Karelian continental margin, with both continental and oceanic lithosphere, which is supported by chronological, petrological, and structural architectures of the profile. This creates new opportunities to directly study the properties of the MLD, which could help understand and settle the controversies on the origin of the MLD and its physical, chemical, and geophysical properties. Highlights • A weak MLD can provide opportunity for lithospheric destruction, when it is connected to the thinned cratonic margins. • A weak MLD can enhance the lithospheric destruction during extension, basal drag and delamination. • Buoyant cratonic roots can be left behind beneath oceanic basins along weak MLDs to form composite oceanic plateaus. • A composite ophiolite profile, with both continental and oceanic lithosphere, is the best place to sample the weak MLD rocks. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • The Mikabu greenstones in SW Japan are fragments of accreted oceanic plateau. • Zircon U-Pb ages from the Mikabu greenstones show an igneous age of 155 Ma. • Zircon trace elements suggest depleted source mantle for the Mikabu protolith. • The Mikabu greenstones were parts of Jurassic oceanic plateau like Shatsky Rise. Abstract The Mikabu greenstones form accreted fragments of an ancient oceanic plateau, which are currently incorporated within the Cretaceous high P/T-type Sanbagawa metamorphic belt in SW Japan. Previous geological and petrological studies indicate that protoliths of the Mikabu greenstones were mafic/ultramafic volcano-plutonic rocks of oceanic plateau and/or islands. Despite their rock assemblage and metamorphic nature, their protolith age has been poorly constrained. By measuring U-Pb age of igneous zircon grains using LA-ICPMS, this study identified for the first time a Late Jurassic age for the protoliths of the Mikabu greenstones in the eastern Kii Peninsula (the Shurei complex). With an overlap within 2-sigma error, measured U-Pb ages of zircon grains have a weighted mean age of 154.6 ± 1.6 Ma (the Kimmeridgian, Late Jurassic), which is slightly younger than the radiolarian ages (Middle Jurassic) of deep-sea pelagic cherts associated with the Mikabu greenstones. This age difference indicates that mafic magmas intruded pelagic deep-sea sediments to form a volcanic edifice onto the pre-existing oceanic lithosphere. New measurements of trace element composition of the dated zircon grains further confirmed that the dated zircon grains are more similar to those in oceanic crusts rather than in continental crusts. In addition, the trace element composition suggests that the host mafic magma of the zircon grains was derived from depleted mantle similar to the mid-oceanic ridge-type source, rather than fertile mantle source like Hawaii and Iceland. On the basis of the common occurrence of similar mafic rocks from the Shatsky Rise in the modern NW Pacific Ocean, we conclude that the protoliths of the Mikabu greenstones had formed a part of an oceanic plateau/island, which was generated by the Late Jurassic intra-plate mafic magmatism in ancient mid-Pacific, probably together with the Shatzky Rise. [ABSTRACT FROM AUTHOR]

Subduction initiation is a crucial process for plate tectonics. Two scenarios of induced subduction initiation–subduction polarity reversal and subduction transference–are primarily attributed to the accretion of oceanic plateaus. However, the factors governing these two distinct types of subduction initiation remain elusive. Here, we employ 2D thermomechanical numerical models to investigate the dynamics of induced subduction initiation during oceanic plateau accretion. Specifically, we explore the impact of the thickness, density, and rheological strength of the oceanic plateau on subduction initiation. Our results reveal three geodynamic regimes: continuous subduction, subduction transference, and subduction polarity reversal. Thin oceanic plateaus tend to subduct along with slabs into the deep mantle, while thick oceanic plateaus often accrete to the margin, triggering subduction initiation. The rheological strength and density of an oceanic plateau play a significant role in determining whether subduction transference or polarity reversal occurs. Increasing the viscosity and decreasing the density of the oceanic plateau promotes strain concentration in front of the oceanic plateau, resulting in subduction polarity reversal. Our model results provide insights into the dynamics of subduction transference in the Caroline Sea and polarity reversal in Solomon in the western Pacific Ocean. • Numerical modeling of subduction transference and polarity reversal. • The styles of induced subduction initiation depend on the rheological strength and density of an oceanic plateau. • The formation of the lithospheric-scale shear zone is critical forthe type of induced subduction initiation. • The dynamics of two subduction initiations in the western Pacific Ocean are interpreted and analyzed. [ABSTRACT FROM AUTHOR]

The Caicedo Tuffs is a recently mapped Paleogene volcanic arc unit in the northern Andes, which provides insight into the magmatism of northwestern South America following its collision with the Caribbean-Colombian Oceanic Plateau (CCOP) in the latest Cretaceous. New regional geological mapping, igneous petrography, whole-rock and pyroxene geochemistry, and zircon U-Pb dating are provided for the northern sector of the eastern flank of the Western Cordillera of Colombia (Antioquia). These data reveal that the Caicedo Tuffs unit is predominantly composed of primary volcaniclastic deposits (tuff to breccia) that record mafic subaqueous volcanism and limited orogenic building shortly after collision of the CCOP. The geochemistry of these deposits includes major element characteristics and immobile trace element patterns that are typical of boninites. Zircons from these igneous rocks constrain a crystallization age of ca. 57 Ma, with meso-Proterozoic to Jurassic inherited zircons most likely reflecting continental recycling by turbidites in the subduction zone. The boninitic affinity of the Caicedo Tuffs and existing regional igneous and tectonic constraints can be explained by resuming of subduction and/or sinking of an older oceanic slab along northern South America following collision of the CCOP with South America. The boninitic, primary volcaniclastic deposits of the Caicedo Tuffs are crosscut by basaltic-gabbroic sills and dykes with oceanic plateau-like geochemical affinities, which lack evidence for hydrous melting and are compositionally similar to igneous rocks of the CCOP. These intrusions are interpreted to reflect decompression melting of plume-related mantle inherited during the collision of the CCOP with South America or slab detachment. The occurrence of oceanic plateau-like intrusions in a Paleocene volcanic arc casts doubt on the origin of other oceanic plateau sequences of the Western Cordillera, which are generally attributed to the Cretaceous CCOP. The Caicedo Tuffs is a unique boninite unit of which the detailed spatiotemporal extent and petrogenesis remain to be constrained, but that can provide valuable insight into tectono-magmatic processes during oceanic plateau-continent collision. • A new ca. 57 Ma-old submarine volcanic arc unit is documented in the NW Andes. • It records magmatism after collision of the Caribbean oceanic plateau with S America. • It includes Tonga-like boninites unlikely formed by typical subduction initiation. • Meso-Proterozoic to Paleocene zircons occur in the boninites. • The boninites are crosscut by oceanic plateau-like intrusions. [ABSTRACT FROM AUTHOR]

The Raspas Metamorphic Complex is a high-pressure unit that includes eclogites, blueschists, and metapelites, with minor garnet amphibolites and greenschists. Although its geochemistry and ages are relatively well known, metamorphic constraints and the origin of its protolith remain unclear. In this study, we present new geochemical, metamorphic, and cooling age data to understand the protolith, metamorphic conditions, and the tectonic implications of this feature for the Northern Andes. Geochemical analyses reveals rocks with N- to E -MORB signatures and trace element ratios typical of a heterogeneous mantle source, like oceanic plateau lavas. Blueschists originated from a deep enriched source, similar to primitive mantle, while eclogites are similar to MORB. Iterative thermodynamic modeling of an eclogite indicates a low T/P gradient of ∼406 °C/GPa during the formation of the assemblage garnet (core), quartz, katophorite, and omphacite cores at ∼598 °C and 1.43 GPa, followed by the formation of atoll garnets and zoisite at 661 °C and 1.63 GPa, around 133 Ma. Peak metamorphic conditions were attained after isobaric heating at 709 °C and 1.61 GPa, resulting in the assemblage of garnet (rim), zoisite (rim), omphacite (rim), and katophorite. 40Ar/39Ar ages around 129 Ma indicate fast exhumation rates of 1.25 to 0.5 cm/yr. We propose that the Raspas Metamorphic Complex represents the interaction of the South American plate with an oceanic plateau during the Early Cretaceous. During the early stages of subduction, it created a flat slab geometry around 130 Ma. As the plateau transformed to eclogite, the decrease in buoyancy caused an increase in subduction dip during a regional roll-back at 129–123 Ma, which triggered the exhumation along the high-pressure belt. • Eclogite register the subduction and exhumation of an oceanic plateau. • The Northern Andes interacted with another oceanic plateau in the Early Cretaceous. • Fast exhumation rates of 1.25 to 0.5 cm/y after isobaric heating caused by a rollback. [ABSTRACT FROM AUTHOR]