GD1.2 | Structure, origin, and evolution of intraplate magmatism in space and time; insights from petrological, geochemical and geophysical studies
EDI
Structure, origin, and evolution of intraplate magmatism in space and time; insights from petrological, geochemical and geophysical studies
Co-organized by GMPV10
Convener: Martha PapadopoulouECSECS | Co-conveners: Jordan J. J. PhetheanECSECS, Magdalena Matusiak-Małek, Matthew J. Comeau, Lara Kalnins, Ingo Grevemeyer
Orals
| Thu, 18 Apr, 08:30–10:15 (CEST)
 
Room -2.91
Posters on site
| Attendance Fri, 19 Apr, 10:45–12:30 (CEST) | Display Fri, 19 Apr, 08:30–12:30
 
Hall X2
Orals |
Thu, 08:30
Fri, 10:45
The introduction of the plate tectonics theory in the 1960s has been able to satisfactory explain ~90% of the Earth’s volcanism, attributing it to either convergent or divergent plate boundaries. However, the origin of a significant amount of volcanism occurring on the interior of both continental and oceanic tectonic plates – widely known as intraplate volcanism – is considered to be unrelated to common plate boundary processes. A variety of models have been developed to explain the origins of this enigmatic type of magmatism. With time, technological breakthroughs have enabled improvement of instrumentation, resolution, and numerical modelling, as well as the development of new techniques that allow us to better understand mantle dynamics in the Earth’s interior. This technological improvement has helped re-evaluate and refine existing models and develop new models on the origins of intraplate magmatism. These models in turn, provide better insights on processes at depth, and also shed light on the complex interactions between the mantle and the surface. Understanding what triggers magmatism away from plate boundaries is critical to understand and reconstruct the evolution of Earth’s mantle through time, especially in eras where the tectonic plates weren’t yet developed or when the surface of the Earth was dominated by supercontinents. Investigating the relationship between the kinematics and mechanics of the tectonic plates on the one hand and the mantle dynamics on the other can give insights on the impact of the magmatism on the plates themselves. Moreover, deciphering the origins of intraplate magmatism on Earth can give us invaluable knowledge towards understanding magmatism on other planetary bodies in the solar system and beyond.
We welcome contributions dealing with the origins and evolution of intraplate magmatism, both in continental and oceanic settings, using a variety of approaches and techniques to tackle outstanding questions, such as but not limited to: petrological, geochemical, geochgronological and isotopic data, geophysical and geodynamical analysis, and seismological data. The aim of the session is to bring together scientists looking to understand intraplate magmatism using different approaches and to enhance discussion and collaboration between the various disciplines.

Orals: Thu, 18 Apr | Room -2.91

Chairpersons: Martha Papadopoulou, Matthew J. Comeau, Lara Kalnins
08:30–08:35
08:35–08:45
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EGU24-473
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ECS
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On-site presentation
Zakaria Boukhalfa, Matthew J. Comeau, Amel Benhallou, Abderrezak Bouzid, and Abderrahmane Bendaoud

Continental intraplate volcanic systems, with their location far from plate tectonic boundaries, are not well understood: the crustal and lithospheric mantle structure of these systems remain enigmatic and there is no consensus on the mechanisms that cause melt generation and ascent. The Cenozoic saw the development of numerous volcanic provinces on the African plate. This includes the Hoggar volcanic province, located in Northwest Africa, part of the Tuareg shield. It is composed of several massifs with contrasting ages and eruptive styles. The magmatic activity began at around 34 Ma and continued throughout the Neogene-Quaternary. Phonolite and trachyte domes as well as scoria cones and necks are found in the Manzaz and Atakor volcanic districts. In order to image the crustal and lithospheric mantle structure of this region, and to understand the origins and potential mechanisms of the continental intraplate volcanic activity in the Central Hoggar and specifically the Atakor/Manzaz area, we acquired magnetotelluric (MT) measurements from 40 locations and generated a 3-D electrical resistivity model. The model covers an area of about 100 km by 200 km. Images of the subsurface architecture, in terms of electrical resistivity, from the near-surface to the lithospheric mantle, allow us image the deep plumbing system of the volcanic system. Low resistivity features (i.e., conductors) in the crust that are narrow, linear structures trending approximately north-south, are revealed along the two boundaries of the Azrou N’Fad terrane, in the Manzaz area. They likely reflect the Pan-African mega-shear zones, which were reactivated throughout the tectonic evolution of the region. The model reveals that these faults are lithospheric-scale. In addition, the low-resistivity features likely represent the signatures of past fluid flow. The location of the recent Cenozoic volcanic activity was likely influenced by the pre-existing structure. A deep feature of moderate conductivity is located in the upper lithospheric mantle directly beneath the Manzaz and Atakor Volcanic Districts. It may represent the origin of the overlying anomalies and may suggest metasomatism of the sub-continental lithospheric mantle.

Keywords:  intraplate, Hoggar, alkaline volcanism, magnetotelluric, electrical resistivity.

How to cite: Boukhalfa, Z., J. Comeau, M., Benhallou, A., Bouzid, A., and Bendaoud, A.: Deep plumbing model of the Cenozoic Manzaz / Atakor intraplate volcanic system, Central Hoggar, Northwest Africa, based on electrical resistivity models, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-473, https://doi.org/10.5194/egusphere-egu24-473, 2024.

08:45–08:55
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EGU24-13068
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ECS
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On-site presentation
Juan Camilo Meza, Jan Inge Faleide, Alexander Minakov, and Carmen Gaina

The Eurasia Basin, one of two major oceanic basins of the Arctic Ocean, is composed of the Amundsen and Nansen basins, which were created due to the slow and ultra-slow seafloor spreading at the mid-oceanic Gakkel Ridge initiated during the Paleocene-Eocene transition (53-56 Ma). Since the beginning of the current millennia the Gakkel Ridge and the Eurasia Basin have been subject of marine geological and geophysical studies leading to the collection of diverse datasets including rock samples, seismic, and potential-field datasets. New marine seismic data has become available in the western Eurasia Basin in the very last years, including data acquired by the Norwegian Petroleum Directorate in the context of the UN Law of the Sea, together with seismic lines gathered by Norwegian research institutions and partners. During October-November 2022 the first High Arctic GoNorth marine expedition collected new seismic reflection and refraction, as well as gravity and magnetic datasets. It is considered that this polar region may hold important clues for the understanding of global processes such as passive margin formation, and the complex links between plate tectonics and climate. Volcanic additions have been suggested within the flanks of the Eurasia Basin during different stages in the Cenozoic. Existing hypotheses further postulate corridors of exhumed mantle formed across the western Eurasia Basin because of the magmatic segmentation imposed by the Gakkel Ridge. Consequently, the oceanic basement of this area should be prone to deformation, hydrothermal alteration and serpentinization. However, little is known about the relationships between such processes with the sedimentary units above, or whether such processes occur away from the ridge and to what extent.

The new compilation of multi-channel seismic reflection profiles provides an image of the sedimentary structure and the upper crust, within the oceanic crust and the continent-ocean transition (COT) between northern Svalbard margin and Eurasia Basin. The preliminary analysis of these datasets indicates that the sediments and basement structures within the southwestern corner of the Eurasia Basin have been modified in a unique manner due to an underlying geothermal anomaly beneath the lithosphere. This is expressed as focused late Miocene (< 20 Ma) to recent sill intrusion events resulting in basement and sediment deformation, and intense hydrothermal and sediment evacuation features. We present unique examples of hydrothermal venting on seismic reflection data and discuss implications of the post-rift NE Atlantic and Arctic setting, including the role of breakup magmatism, post-breakup intraplate volcanism, and sheared/passive margin development during the Cenozoic.

How to cite: Meza, J. C., Faleide, J. I., Minakov, A., and Gaina, C.: Intraplate magmatism, serpentinization and hydrothermal venting in the ultra-slow spreading setting of the Eurasia Basin, Arctic Ocean, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13068, https://doi.org/10.5194/egusphere-egu24-13068, 2024.

08:55–09:05
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EGU24-3168
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ECS
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On-site presentation
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Luizemara Szameitat, Monica Heilbron, Alessandra Bongiolo, Otavio Licht, Maria Alice Aragão, and Francisco Ferreira

The Parana Basin is one of the larger continental Paleozoic basin in Central South America. Although several studies investigated the flooring mantle of the Parana Basin, mantle-scale oceanic relicts have not been interpreted by previous regional geophysical studies. For this work, we used the global-scale tomographic model of P-wave velocity perturbation UU-P07 for mapping slab-like anomalies, and qualitative gravity and magnetic anomalies for indicating orogenic trends. Positive P-wave anomalies were mapped along fifty-two profiles, and revealed slab-like anomalies (long and segmented tabular mantle bodies), and four top slab surfaces (S1, S2, S3 and S4). The biggest anomalous mantle body (top surface S1) is transversal to the central-southern Brasilia Belt trending, and therefore it can be directly linked to the Southern São Francisco craton. However, the other three slab-like tabular bodies cannot be linked to outcropping orogenic trends, due to the extensive and thick sedimentary cover of the Parana Basin. Southwestern São Francisco Craton, elongated bodies coincide with Brazilian/Pan-African island arc collisions (top surface S2), but other possible slabs (top surfaces S3 and S4) are underneath Paraná Basin. Positive anomalies in the residual geoid anomalies (XGM2019e_2159 model) and transformed total magnetic field (vertical integration) follow the possible accretionary trend formed by S2, S3 and S4. Although the assumptions about the origin of these slab-like anomalies need to be investigated further, all these observations have shown the high complexity of the upper mantle beneath Parana floods. Facing the geophysical anomalies, we realize that the mapped slab-like bodies are mostly located under the Central-Northern Parana Basin, where several studies interpreted the existence of remnants of Proterozoic subductions in the mantle. Previous geochemical analysis had linked the high-Ti domain in the Central-Northern Parana floods with the partial melting of oceanic subduction relics. Nonetheless, the abundance of other incompatible elements (e.g., P, F and B) in the early phase of Central-Northern basaltic floods can be inherited from subduction remnants in the mantle. The remarkable early enrichment contrasts with the primitive mantle affinity in tholeiitic magmas of the relative late northern floods of the Parana Basin, the southern floods of the Parana Basin, the Etendeka counterpart, and the continental margins. In agreement with the previous understanding of the chemical evolution, we consider that the early magmatic phase was highly influenced by subcontinental subduction relicts. On the other hand, the advancing lithospheric embrittlement, due to the Atlantic opening process, intensified the rise of primitive fluids. Therefore, geophysical observations support the hypothesis of the existence of oceanic remnants from oceanic closure southern São Francisco Craton, due to the Western Gondwana’s assembly. The location of highly preserved oceanic-like mantle bodies supports the occurrence of enriched magmas in the early magmatic phase of the Northern Parana-Etendeka LIP.

How to cite: Szameitat, L., Heilbron, M., Bongiolo, A., Licht, O., Aragão, M. A., and Ferreira, F.: Oceanic remnants in the mantle of the Parana Basin, Central South Atlantic: supporting the large-scale geochemical anomaly in the Northern Parana-Etendeka LIP, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-3168, https://doi.org/10.5194/egusphere-egu24-3168, 2024.

09:05–09:15
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EGU24-14572
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ECS
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On-site presentation
Lithosphere thinning and welding by Reunion Hotspot: impingement timing, transitional state and dynamics of Deccan Volcanic Province. 
(withdrawn)
Siddharth Dey, Debojit Talukdar, Avisekh Ghosh, Amarjeet Bhagat, Chiluvuru Kumar, Manoranjan Mohanty, and Ashish Raul
09:15–09:25
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EGU24-4616
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On-site presentation
Yanghui Zhao, Bryan Riel, Hanghang Ding, and Dazhen Deng

Seamounts are theorized to originate from deep mantle plumes or shallow, plate-related activities. The mantle plume hypothesis suggests that abnormally hot materials rise from the lowermost mantle and produce large volumes of volcanism on the surface. However, the accuracy of morphological analysis and volume estimation is highly influenced by the representation accuracy of irregularly shaped seamounts and the extent to which thick sediment coverage obscures their bases. As a result, the precise contribution of magma from mantle plumes to surface volcanism remains unclear.

Our study introduces a novel approach using Gaussian Process Regression to reconstruct the complex topography of seamounts, both above and beneath sedimentary covers. This approach advances previous analyses by (1) taking account of irregular seamount topography and (2) correcting for the varying sediment thicknesses that obscure seamount bases. Our investigation yields two principal findings.

1. Refined Volcanism Distribution Mapping

Analysis in the Pacific Ocean indicates that only 18% of total intraplate volcanic activity is attributable to plume-related volcanism. In addition, the volume statistics of plume-related seamounts and those along the Large Low-Shear-Velocity Province margins show no significant distinction from those of other intraplate seamounts. These results suggest that proposed plumes account for only a minority of the volume of intraplate volcanism in the Pacific plate, and that shallow rather than deep processes are dominant.

Along the volcanic Kyushu-Palau Ridge, high seamount volumes are observed near lithospheric weak zones, implying that tectonic inheritance significantly influences magma distribution during volcanic arc formation.

2. Comprehensive Morphological Analysis

Employing machine learning clustering analysis on high-resolution multibeam bathymetry data, we categorize seamounts in the South China Sea basin into three distinct morphological types: Type I, large seamounts with steep slopes and rounded bases, predominantly located along extinct ridges; Type II, linear seamounts characterized by gentler slopes, situated along ridges; and Type III, smaller, elliptically-based seamounts found along transform faults or off-ridge areas. This morphological classification provides a novel quantitative framework correlating seamount shapes with their tectonic environments during volcanic activity.

Overall, this research advances our understanding of seamount genesis, highlighting the importance of shallow tectonic processes in shaping submarine volcanic landscapes.

How to cite: Zhao, Y., Riel, B., Ding, H., and Deng, D.: Understanding Seamount Genesis: Utilizing Gaussian Process Regression and Clustering for Morphological Analysis, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4616, https://doi.org/10.5194/egusphere-egu24-4616, 2024.

09:25–09:35
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EGU24-13934
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ECS
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On-site presentation
Lingtong Meng, Chu Yang, Wei Lin, Ross N. Mitchell, and Liang Zhao

Establishing the mechanisms for craton modification is critical for understanding cratonic stability and architecture. Cratons are intrinsically strong with long-term stability, but plate tectonics or mantle plumes cause craton weakening, mechanical decoupling, and lithospheric removal. By comparison, craton modification—craton destruction accompanied or followed by rejuvenation—has received less attention. Oceanic plate subduction dominantly destroys the craton, with a lesser degree of rebuilding. Mantle plumes can facilitate decratonization, by weakening and peeling off the lithospheric mantle, or recratonization, by healing the craton with refractory mantle residues. Compared with the effects of oceanic plate subduction and mantle plumes, the role of continental subduction in craton modification remains an open question. The North China Craton (NCC), a previously stable continent with a lithospheric thickness of >200 km since the Paleoproterozoic, was reworked and partially destroyed due to lithospheric delamination triggered by Early Cretaceous Paleo-Pacific oceanic subduction. In eastern NCC, lithospheric thickness decreased from 200 km to 35 km in the Early Cretaceous in only 10 m.y. The NCC experienced an early Mesozoic continent–continent collision (as the overriding plate) with the South China Block (SCB). The collision provides an opportunity to understand the potential for craton modification due to deep continental subduction induced by continental collision.

In the NCC, combined structural geology, magnetic fabrics, zircon U-Pb dating, and Hf-O isotopes, we report the presence of martial derived from a partially melted SCB’s crust. We proposed a three-stage model to interpret the material sourced from the subducted plate into the overriding carton: (1) SCB bulldozed and rebuilt NCC during 250–220 Ma; (2) during 220-200 Ma, the subducted SCB exhumed along the exhumation channel to underplate beneath the NCC, associated with partial melting; (3) finally, Late Jurassic granite derived partial melting of the SCB entrained Latest Triassic reworked SCB’s crust to emplace.

Combining our new results with previous geophysical observations, we estimate the extent of the bulldozing and rebuilding. We argue that a 200-km-long tract of the NCC lithosphere was bulldozed and rebuilt by the subducted SCB, resulting in a lithospheric suture far from the suture zone at the surface. This lithospheric removal occurred at middle-lower crustal levels (16–20 km depth)—much shallower than previously thought possible. The bulldozed NCC lithosphere was replenished by the subducted SCB continental lithosphere rather than the asthenosphere, thus terminating the lithosphere modification. With essentially no net loss of lithosphere during deep continental subduction, the NCC maintained its stability until Early Cretaceous paleo-Pacific oceanic subduction. This “bulldoze and rebuild” model can thus account for how a craton maintains its stability during a collision with another continental plate.

How to cite: Meng, L., Yang, C., Lin, W., Mitchell, R. N., and Zhao, L.: Bulldoze and rebuild: Modifying cratonic lithosphere via removal and replacement induced by continental subduction, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13934, https://doi.org/10.5194/egusphere-egu24-13934, 2024.

09:35–09:45
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EGU24-14228
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ECS
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Virtual presentation
Egor Koptev and Alexander Peace

Mesozoic intraplate igneous activity is abundant on the Canadian shield and includes multiple kimberlite fields, a province of alkaline magmatism, and individual bodies of kimberlites and ultramafic lamprophyres. Models have variously attributed the emplacement of these intrusions to the influence of Farallon plate subduction, opening of the Atlantic Ocean, or one or several Atlantic hotspots which North American plate is postulated to have drifted over during the Mesozoic. The latter hypothesis relies of the attribution of spatially, temporally and compositionally distributed and diverse magmatic rocks into a poorly defined, age-progressive, ‘corridor’ which may be derived from a common geochemical reservoir. In this study, we aim to test the spatiotemporal association between intraplate igneous activity along this postulated Triassic-Jurassic corridor and several elements of fixed mantle reference frame, such as the Atlantic hotspots and the hypothesised plume-generating zone (PGZ) of the African Large Low Shear Velocity province (LLSVP).

We use published geochronological databases containing locations and isotopic ages of the Mesozoic intrusions of North America and published global plate reconstructions to dynamically calculate distances between the loci of intraplate magmatism and features of the upper and lower mantle assuming the latter remained fixed in the mantle reference frame throughout their history. We use GPlates 2.3.0 software package and pygplates 0.36.0 Python library to build the reconstructions and implement our calculations.

Results demonstrate that none of the examined mantle features show a consistent association with all instances of intraplate magmatism across the Canadian shield during the Triassic-Jurassic. The coeval kimberlitic magmatism in the western Slave province (Jericho kimberlite field) and Baffin Island (Chidliak kimberlite field) appears to be completely spatially unrelated to any of the examined mantle features. The kimberlite fields of the Superior province (Attawapiskat, Kirkland Lake, Timiskaming) experience emplacements long before and after their passage over the PGZ, but their frequency increases in the PGZ’s vicinity, i.e. 76% of emplacement events in these provinces occur within 200 km of the PGZ’s surface projection.

Our results show that intraplate magmatism across many Triassic-Jurassic fields of North America could be initiated independently of the influence of deep mantle structures. Thereby, a geodynamic mechanism nested in the asthenosphere or lithospheric mantle suffices for melt generation in an intraplate setting. However, it cannot be ruled out whether proximity to deep mantle structures is capable of facilitating “shallow” melt generation and emplacement and that deep-seated mantle structures could provide an influx of fluids or thermal energy, increasing melting intensity and volume.

How to cite: Koptev, E. and Peace, A.: The Triassic-Jurassic corridor of North America: are deep mantle structures a sufficient explanation for intracontinental magmatism?, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-14228, https://doi.org/10.5194/egusphere-egu24-14228, 2024.

09:45–09:55
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EGU24-14365
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ECS
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On-site presentation
Jung-Hun Song, Seongryong Kim, Junkee Rhie, and Tae-Seob Kang

Intraplate volcanism signifies persistent magmatic activity within plate interiors far from active plate boundaries. However, due to limited assessment of the detailed physical conditions of the intraplate upper mantle, the fundamental mechanism behind the genesis of mantle magma remains poorly understood. We analyzed the temperature conditions of the upper mantle beneath global intraplate volcanic regions estimated from seismic velocity and geochemical data. We revealed that excluding volcanoes near major plumes, large proportions (> 70%) of the volcanoes are situated above the upper mantle with moderate temperatures comparable to or colder than those found at mid-oceanic ridges (potential temperature (Tp) ~1250–1350°C). These volcanoes also overlie regions of low vertical and horizontal asthenospheric shear estimated by global mantle convection simulations. Without peculiarities in thermal and large-scale mantle dynamics, we inferred that these volcanic activities are likely driven by a small-scale local convective process confined to the shallow upper mantle. To constrain a more detailed process of intraplate volcanism, we focus on analyzing the upper mantle rheology and melt distribution beneath intraplate volcanoes in NE Asia. Thermodynamic properties, conservatively constrained by high-frequency seismic attenuation and velocities, revealed the common presence of low-viscosity zones concentrated beneath the volcanoes at shallow asthenospheric depths (< 200 km). These regions contain a small fraction of melt (~0.05–0.8%) at cold-to-moderate temperatures (Tp ~1300–1350°C) compared to the average mantle aligning with global analyses. A series of evidence potentially suggests the existence of localized mantle upflux focused beneath intraplate volcanoes. Considering the amount and extent of the estimated mantle melts and numerical mantle convection simulations with lithospheric structures, we propose that undulations in the lithosphere and asthenosphere boundary could play a primary role in controlling the small-scale mantle convection and the location of intraplate mantle melting. Our estimation supports the possibility of the ubiquitous occurrence of intraplate volcanoes independent of dynamic forces for deriving active mantle upwellings (e.g., thermal or chemical buoyancy).

How to cite: Song, J.-H., Kim, S., Rhie, J., and Kang, T.-S.: Intraplate Volcanism by Spontaneous Shallow Upper Mantle Melt Focusing, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-14365, https://doi.org/10.5194/egusphere-egu24-14365, 2024.

09:55–10:05
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EGU24-14871
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On-site presentation
Fernando Ornelas Marques, Cristina Catita, Anthony Watts, Anthony Hildenbrand, and Sónia Victória

A volcanic edifice much larger than the current one must have existed in Santiago Island, Cape Verde, because the granular rocks and dyke-in-dyke complex representing magma chambers and deep feeders currently outcrop up to 700 m altitude. Therefore, we must find an explanation for the massive destruction of the original edifice. We developed a new tool for the quantitative reconstruction of ancient topographies in a volcanic ocean island to address this problem, because it allows us to estimate the shape and volume of volcanic rock removed at a certain time. The reconstruction of the topography of the basement complex at ca. 6 Ma ago, before the unconformable deposition of the submarine complex, shows a concave depression coincident with the asymmetric distribution of volcanic complexes east and west of the main divide of the island. This concave depression is here interpreted as the remnant of an island-scale, summit collapse. Instituto do Mar de Cabo Verde bathymetry and RRS Charles Darwin (8/85) seismic reflection profile data suggest that the west side of Santiago is characterised by a narrow insular shelf, a major debris avalanche deposit with scattered blocks and at least one lateral sector collapse structure. Data, however, east of Santiago are limited and so the full extent of mass wasting on the east side of the island is not known. Maio Island, which is similar in age to Santiago, would have acted as a buttress in the east, and it is possible that any eastward collapse might have rotated and travelled to the northeast. Irrespective, one or more mass wasting events west or east of Santiago are consistent with a major destruction of the original volcano edifice which removed the summit, exposed the basement complex of the island, and redistributed volcano-clastic material over a large area of the adjacent seafloor. 

How to cite: Ornelas Marques, F., Catita, C., Watts, A., Hildenbrand, A., and Victória, S.: Santiago Island, Cape Verde: Evidence for island-scale collapse from paleotopography onshore and bathymetry offshore, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-14871, https://doi.org/10.5194/egusphere-egu24-14871, 2024.

10:05–10:15
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EGU24-18822
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ECS
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On-site presentation
Chong Xu, Paul Wessel, Anthony Watts, Brian Boston, Robert Dunn, and Donna Shillington

The Hawaii-Emperor seamount chain stretches westward from the “Big Island” of Hawaii for over 6000 km until the oldest part of the chain are subducted at the Kuril and Aleutian trenches. Still regarded as the iconic hotspot-generated seamount chain it has been sampled, mapped, and studied to give insights into numerous oceanic phenomena, including seamount and volcano formation and associated intraplate magma budgets, the past absolute motions of the Pacific plate, the drift of the Hawaiian plume, and the thermal and mechanical properties of oceanic lithosphere. Previous work (Wessel et al., EGU 2023 abstract) used a high-resolution free-air gravity anomaly and high-resolution bathymetry data set, together with fully 3-dimensional flexural models with variable volcano load and infill densities, to estimate the optimal effective elastic thickness, Te, and load and infill densities along the Emperor Seamount chain. Here, we use these parameters to calculate the tectonic tilt of a pre-existing volcano that occurs as each new volcano in a seamount chain is progressively added by flexure to the Pacific oceanic plate. We found tilts in the range 0.1-2.1 degrees which are modest compared to other cases of progressive flexure, for example, at seaward dipping reflector sequences in volcanic rifted margins (~5-15 degrees) but may be significant enough to modify the morphology of volcano summits and the stratigraphy of the sequences that accumulate in their flanking moats. They may also modify the physical properties of the edifice such as their magnetisation vectors.

Wessel, P., A. B. Watts, B. Boston, C. Xu, R. Dunn, and D. J. Shillington “Variation in Elastic Thickness along the Emperor Seamount Chain”, EGU 2023 Abstract

How to cite: Xu, C., Wessel, P., Watts, A., Boston, B., Dunn, R., and Shillington, D.: Plate flexure and tectonic tilt along the Emperor Seamount Chain , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-18822, https://doi.org/10.5194/egusphere-egu24-18822, 2024.

Posters on site: Fri, 19 Apr, 10:45–12:30 | Hall X2

Display time: Fri, 19 Apr 08:30–Fri, 19 Apr 12:30
Chairperson: Martha Papadopoulou
X2.55
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EGU24-1021
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ECS
Anna Marie Rose Sartell, Christoph Beier, Ulf Söderlund, Kim Senger, Grace E. Shephard, Hans Jørgen-Kjøll, and Olivier Galland

Large Igneous Provinces are defined as magmatic provinces with large magma volumes (> 100,000 km3) emplaced and/or erupted in an intraplate tectonic setting over a vast area within a few Myr, thus having the potential for significant impact on the global climate. The High Arctic Large Igneous Province (HALIP) was emplaced during the Cretaceous. The available ages, ranging between ~140 and 80 Ma, suggests that the magmatism was apparently long-lived and multi-phase. Extrusive and intrusive remnants of the HALIP can be found across the circum-Arctic, specifically in Arctic Canada, Russia, Svalbard, Northern Greenland, and the Arctic Ocean. On Svalbard, the HALIP magmatism is regionally called the Diabasodden Suite. Here, the dolerites have mainly been emplaced as sills at shallow depths and occur all over the archipelago. Despite the relative accessibility of outcrops, the HALIP on Svalbard has been mostly unexplored. As such, available U-Pb geochronology of the Diabasodden Suite is limited, but indicates a shorter time span of 125 – 122 Ma.

Yearly field campaigns since 2020 have resulted in over 150 collected samples from Spitsbergen and Nordaustlandet. This has been accomplished through a collaborative effort, and by strategically targeting outcrops to build a good representative dataset of the Diabasodden Suite. Additionally, a large number of samples have also been taken for a detailed case-study in central Spitsbergen. The dolerite samples are used for whole-rock major and trace element geochemical analysis, U-Pb baddeleyite geochronology and petrological studies. Furthermore, during all field campaigns, high-resolution drone images have also been acquired. These data form the basis for digital outcrop models (DOMs), which are used for thickness measurements of the sills and to put the geochemical data into a 3D perspective. The resulting DOMs are made openly available through the geoscientific database of Svalbard, SvalBox.

Here we present a review of the available geochronology of the HALIP in the circum-Arctic, as well as new data from Svalbard. Specifically, new U-Pb baddeleyite ages of one mafic sill in northern Isfjorden, and an extensive dataset of whole-rock geochemical data from the HALIP on Svalbard to better understand the magmatic history of the HALIP as a whole.

How to cite: Sartell, A. M. R., Beier, C., Söderlund, U., Senger, K., Shephard, G. E., Jørgen-Kjøll, H., and Galland, O.: Geochemistry and geochronology of the High Arctic Large Igneous Province on Svalbard, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-1021, https://doi.org/10.5194/egusphere-egu24-1021, 2024.

X2.56
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EGU24-1799
Alexander Peace and Gillian Foulger

The origin of intraplate magmatism is debated, with two main hypotheses having been proposed. These are deep-seated high-temperature sources (plumes), and  intraplate extension driven ultimately by plate tectonics. A test region in this debate is the 'Jurassic Corridor,' a geological feature proposed to span North America, which contains igneous rocks including kimberlites that are attributed to the Great Meteor Hotspot (GMH). Despite longstanding assumption of this model, close inspection using modern, much-expanded geological information sets shows that the existence of a Jurassic Corridor and GMH lacks support. In this paper we reassess the distribution of kimberlites in North America and on neighboring landmasses. We demonstrate the lack of a clear Jurassic Corridor and show instead that the kimberlites and related rocks are more likely linked to the breakup of the Pangaean Supercontinent and controlled by lithospheric structures. Furthermore, by comparing these findings with global plate models for the last 300 Myr we identify three prominent age peaks in North American kimberlite occurrence that broadly align with periods of heightened plate velocity with respect to Africa. Additionally, the analysis reveals in Africa two peaks in kimberlite abundance and two velocity peaks with respect to North America. Here, however, the velocity peaks occurred approximately 20-30 Myr before the kimberlite abundance peaks. These observations underscore the significance of plate kinematics in controlling kimberlite magmatism and add to a growing body of work linking periods of tectonic upheaval to kimberlite production. The implications of this extend to our broader understanding of intraplate magmatism and warrant a global revaluation of similar phenomena.

How to cite: Peace, A. and Foulger, G.: Beyond the Jurassic Corridor: Exploring North American Kimberlites and their relationship to plate tectonics, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-1799, https://doi.org/10.5194/egusphere-egu24-1799, 2024.

X2.57
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EGU24-6451
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ECS
Megumi Fujimoto, Robert Dunn, and Chong Xu

Volcanic seamount chains are widespread throughout ocean basins, but their formation and structure are not well understood. Active-source refraction seismology can provide images of the interiors of these volcanoes via P wave travel time tomography, but that requires proper identification of seismic phases that are generated by and propagate across complex volcanic structures. Unfortunately, the current limitation on the number of seismic phases that can be included in tomographic analyses leads to less detailed images and a limited geological understanding of the structures being imaged. The primary objective of this study is to compare recorded seismic wavefields from recent surveys across the Hawaiian-Emperor Seamount Chain with synthetic wavefields generated through waveform modeling. We use simplified yet realistic models of volcanic edifices, the underlying oceanic crust, and the mantle to better understand observed seismic phases and their origins. In previous studies (Dunn et al., 2019; Watts et al., 2021; Xu et al., 2022; MacGregor et al., 2023), several seismic phases were identified in recorded sections along the Hawaiian-Emperor Chain. However, interpreting the origins of some of these phases remains challenging. In this study, we developed an idealized seamount model based on the seismic structure of Jimmu Guyot in the Emperor Ridge (Xu et al., 2022). We calculated the seismic P-SV wavefield for various source and receiver positions using a finite difference wavefield modeling code (Levander, 1988; Lata and Dunn, 2020). Our goal is to model the observed seismograms and identify additional phases, including P-to-S converted waves. Additionally, we aim to verify recent tomographic images of the Hawaiian-Emperor Seamount Chain created by P wave travel time inversion via wavefield comparison. By resolving ambiguities and pinpointing new seismic phases, our aim is to improve seismic images of the Hawaiian-Emperor Chain. This contribution will enhance our understanding of specific structures, such as volcanic cores (a high-density and high-wave-speed interior core of the seamount), the hypothesized magmatic underplating of the oceanic crust by mantle melts rising beneath the volcanic chain, and the nature of the Moho and upper oceanic crust beneath these volcanic edifices.

How to cite: Fujimoto, M., Dunn, R., and Xu, C.: Modeling seismic wave propagation across complex volcanic structures of the Hawaii-Emperor Ridge, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6451, https://doi.org/10.5194/egusphere-egu24-6451, 2024.

X2.58
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EGU24-7314
Feiyu Lin, Liang Qi, Nan Zhang, and Zhen Guo

Unique intraplate volcano eruptions and westward volcano migration since the Oligocene are observed in NE China, an overriding continental zone tectonically controlled by the subduction of the northwestern Pacific plate and the opening of Japan Sea. Interestingly, these intraplate magmatic events occur around a subsiding basin (the Songliao Basin), but no volcanic activities have been observed within the Songliao Basin. The geodynamic mechanism responsible for these volcanoes remains unclear. To address the geodynamic process beneath NE China, numerical experiments are conducted constrained by datasets from regional reconstruction, seismic and volcanic studies. Vertical velocity field of mantle convection and lithospheric partial melting structures yielded from our numerical model show mantle upwelling and melting center migrates from the east to the west of NE China with the westward propagation of the stagnant slab, leading to the volcano migration. Also, with the subduction retreat of NW Pacific plate and the opening of the Japan Sea, significant lithospheric thickness differences between Changbaishan-Mudanjiang Region and the Songliao Basin develop, leading to lithospheric unstable dripping. This dripping structure prevents the partial melting of the lithosphere but facilitates the subsidence of the Songliao Basin in central NE China. Moreover,  the lithospheric dripping model successfully predicts upper mantle structures consistent with the proposed tomography model, the observed Moho depth, and surface topography variations. Thus, the lithospheric dripping induced by lithospheric thickness difference and the subduction of the Pacific slab provides a robust mechanism for the unique geodynamic process in NE China.

How to cite: Lin, F., Qi, L., Zhang, N., and Guo, Z.: An ongoing lithospheric dripping process beneath Northeast China and its impact on intraplate volcanism, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7314, https://doi.org/10.5194/egusphere-egu24-7314, 2024.

X2.59
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EGU24-11775
Nino Sadradze, Shota Adamia, Sierd Cloetingh, Alexander Koptev, and Guga Sadradze

Transcaucasus - the westernmost part of the southern Caucasus, represents an area where the Tethys Ocean was closed in the Late Cenozoic because of Eurasian and Africa-Arabian plate convergence. The lithosphere of the region represents a collage of Tethyan, Eurasian, and Gondwanan terranes. During the Late Proterozoic–Early Cenozoic a system of island arc and back-arc basins existed within the convergence zone. Geological and palaeogeographical data supported by paleomagnetic studies indicate the presence of several tectonic units in the regions that have distinctive geological histories.

The region comprises a 30-55 km thick continental crust with significant lateral variations in thickness of the overlying sediments (0-25 km). The travel times velocity anomalies of the P- and S-waves are interpreted as high-velocity bodies down to about 100 km depth, where the mantle lithosphere is thin or even missing.

The Mesozoic-Cenozoic magmatic assemblages reflect a diversity of paleogeographic -paleotectonic environments. They are indicative of a west Pacific-type oceanic basin setting under which the mature continental North Transcaucasian arc developed with zones of rifting and alkaline basaltic volcanism on the active margins of the oceanic domain.

Within-plate magmatic activity in the North Transcaucasus is represented by volcanic and plutonic complexes, including Late Triassic to Early Jurassic subaerial alkali basalts and alkali gabbro; the Late Bathonian-Late Jurassic high titanium alkali basalts and minor trachytes with coal-bearing shales and evaporites intercalations; Albian alkali basalts alternating with redeposited volcaniclastics and shallow marine carbonates.

The Late Cretaceous volcanics are associated with intraplate-type titanium rich alkali basalts and basanites with minor trachytes and phonolites, while the Eocene volcanics are associated with highly potassic to ultrapotassic basalts and basanites. The Late Miocene-Pleistocene volcanism is represented by alkaline basalt-trachytes as well.

The Great Caucasus, a NW–SE-directed mountain range, extends westwards along the pre-Caucasian strip of the Eastern Black Sea and is bounded to the south by the Transcaucasian Massif. The shoreline of the Eastern Black Sea Basin cuts off the Colchis intermontane trough formed over the rigid Georgian Block, the Achara–Trialeti trough and the Artvin–Bolnisi rigid block.

Onshore and offshore data confirm that the subaerial structures have immediate submarine prolongations. Deep drilling conducted within the onshore zone of the Transcaucasus, in the immediate vicinity of the shoreline, revealed that the volcanic formations below the modern sea level extend further into the Eastern Black Sea basin.

Recent data on structure and evolution of the Transcaucasus and adjacent area provide new constraints on the geological history of the lithosphere of the region, particularly on the Eastern Black Sea basin located in the collision zone between Eurasian and Africa-Arabian lithosphere plates, proximal to ancient sutures.

How to cite: Sadradze, N., Adamia, S., Cloetingh, S., Koptev, A., and Sadradze, G.: TRANSCAUCASUS: Record of 200 My plume activity, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11775, https://doi.org/10.5194/egusphere-egu24-11775, 2024.

X2.60
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EGU24-12916
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ECS
Kyriaki Daskalopoulou, Samuel Niedermann, Franziska D.H. Wilke, Martin Martin, and Heiko Woith

The western Eger Rift (Czech Republic) is a non-volcanic rift setting of intraplate seismicity that is characterized by abundant degassing of mantle-derived fluids. Since 2019, gases obtained from the free gas phase and volcanic rock samples of Quaternary age have been collected in order to determine the origin and evolution of volatiles in the system and define the magma chamber p-T conditions. Results of the CO2-dominated gas discharges of the Bublák and Hartoušov mofette fields yield an ~93 % mantle input (considering a subcontinental lithospheric mantle) for He. Ne isotopic ratios range from 9.8 to 11.0 for 20Ne/22Ne and from 0.0282 to 0.0480 for 21Ne/22Ne. Notwithstanding the samples enriched in 20Ne likely due to mass fractionation, many samples show a mixed atmospheric-mantle type source for Ne. However, an additional crustal input cannot be excluded. 40Ar/36Ar ratios also cover a wide spectrum of values (between 300 and 4680). Overall, gas samples typically present a higher-than-atmospheric value with 40Ar likely deriving from the mixing of an atmospheric and deep source. The 4He/40Ar* ratio is moderately constant and falls within the MORB range, suggesting an unfractionated magma that originates from mantle sources.. Results obtained from mineral quantitative analyses and by using thermobarometry of orthopyroxene and clinopyroxene rim pairs of matrix grains yield predominantly temperature and pressure conditions of 700 ±100 °C and 1.1 ±0.5 GPa, respectively, indicating a lithospheric depth that ranges between 40 - 45 km for 1.5 GPa and 20-25km for 0.5 GPa. In addition, pairing cores of mm-sized pyroxenes point to a temperature of 1100 ±100 °C and a pressure of 2.5 ±0.5 GPa that correspond to a lithospheric depth of ~75 km. Those minerals that indicate greater depths are likely the oldest ones as they were able to grow for longer times during their ascent. On the other hand, secondary overgrowths or smaller matrix grains represent younger grains that have grown during magma evolution. Therefore, their diverse chemistry and the wide range of p-T conditions reveal rising (and cooling) of magma.

This research is a part of the “MoRe-Mofette Research” and MoCa - “Monitoring Carbon” projects, which were funded by the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) – 419880416, 461419881.

How to cite: Daskalopoulou, K., Niedermann, S., Wilke, F. D. H., Martin, M., and Woith, H.: First insights into the geochemical and petrological features of the Eger Rift’s plumbing system (Czech Republic), EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12916, https://doi.org/10.5194/egusphere-egu24-12916, 2024.

X2.61
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EGU24-13901
Robert Dunn, Megumi Fujimoto, Chong Xu, Anthony Watts, Brian Boston, and Donna Shillington

Some prior active-source seismic studies beneath oceanic seamount chains indicate a sub-crustal layer of what is considered to be underplated magmatic material. The classic example is the Hawaiian Ridge, where a seismic study in the early 1980s first proposed the existence of such a layer. Since then, Hawaii has been considered one end-member in a range of possible scenarios, extending from underplating to no underplating, but with possible magmatic intrusion into the lower oceanic crust. Magmatic underplating affects mass flux and lithospheric loading calculations. All else being equal, underplating would be expected to lower the amplitude of the gravity anomaly over the crest of the edifice and provide a positive buoyancy force that makes the plate appear more rigid than it actually is. One hypothesis put forward to explain variations in the style of magmatic emplacement at intraplate volcanoes hinges on the age of the lithosphere at the time of volcano formation. In this model, shallow intrusion into the oceanic crust and overlying edifice is favored for seamounts growing on younger lithosphere, while magmatic underplating is favored for seamounts growing on older lithosphere such as Hawaii. However, recent seismic, gravity, and plate flexure studies conducted along the Hawaiian-Emperor Seamount Chain collectively provide clear evidence for shallow magmatic emplacement and contradict the notion of significant magmatic underplating for ages at the time of loading of ~57 Ma (Emperor Seamounts) and ~90 Ma (Hawaiian Ridge). Additionally, reprocessed legacy seismic data has not revealed evidence for underplating beneath the Hawaiian Ridge. In this presentation, results from these recent studies will be shown, compared, and the evidence for a simple mantle structure without underplating will be presented along with seismic synthetic tests that explore the degree of underplating that may be 'hidden' in the data.

How to cite: Dunn, R., Fujimoto, M., Xu, C., Watts, A., Boston, B., and Shillington, D.: Seismic Silence Speaks Loud: No extensive magmatic underplating found in recent seismic studies of the Hawaiian Ridge, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13901, https://doi.org/10.5194/egusphere-egu24-13901, 2024.

X2.62
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EGU24-15020
Yingying Li, Bernhard Steinberger, Sascha Brune, and Eline Le Breton

The Eifel volcanic area in western Germany has been active for tens of million years. Geodetic observations, geochemical analysis and seismological studies all indicate that the source of these long-term volcanic activities is a mantle plume. However, it still remains controversial whether the Eifel plume has a deep origin. This is because the tomography images do not consistently show a continuous plume conduit between the surface and the core-mantle boundary. The Eifel plume is also not associated with any flood basalt province or a clearly age-progressive hotspot track, which is regarded as a key surface feature indicating a deep plume origin. In addition, it has been proposed that the Alpine subduction zone, south-east of the volcanic area, has created a stagnant slab in the mantle transition zone, which might be interacting with the Eifel plume.

Based on the previous studies and observations, our two contrasting hypotheses are as follows: (1) The Eifel plume is not rooted in the lower mantle. In this case, subduction beneath the Alps might trigger a return asthenospheric flow and the ascent of an upper-mantle plume, leading to the formation of intraplate volcanism beneath the European plate. (2) The Eifel plume is assisted from an upwelling in the lower mantle. In this case, the subducting plate might tilt the plume conduit and influence the position where volcanism takes place.

In this study, we apply the Finite-Element-Method geodynamic modeling code ASPECT to model the ascent of the Eifel plume and its interaction with the subducting slab. We design both slab advancing and slab retreating model set-ups, with and without a plume from the lower mantle beneath the subducting plate. We check whether and under what conditions the Eifel plume will be triggered behind the slab due to slab overturn. Preliminary results show that the return flow induced by subduction can help generate an upper-mantle plume and lead to the formation of volcanism. A series of models are also performed to investigate the effects of mantle viscosity and plume temperature on the plume-slab interaction.

How to cite: Li, Y., Steinberger, B., Brune, S., and Le Breton, E.: Intra-plate volcanism generated by slab-plume interaction: Insights from geodynamic modeling of the Eifel plume and its interaction with the European subducting lithosphere beneath the Alpine subduction zone, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15020, https://doi.org/10.5194/egusphere-egu24-15020, 2024.

X2.63
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EGU24-15229
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ECS
Thomas Duvernay and D. Rhodri Davies

Compared to oceanic hotspot tracks, volcanic provinces within Earth's continents generally exhibit more intricate surface characteristics, such as spatio-temporal distribution and geochemical signatures of erupted lavas. These complex surface patterns relate to dynamic interactions in the uppermost convective layer of the mantle, where decompression melting occurs. The Cosgrove Track of Eastern Australia constitutes a compelling example of such continental volcanic activity. Recent studies support a mantle plume having sustained the volcanism and discuss several notable features, such as lithosphere-modulated volcanic activity, plume waning, separate volcanic tracks, and plate-motion change.

Here, we simulate the proposed interaction between the Cosgrove plume and eastern Australia during the past 35 Myr. We design a 3-D analogue of the Australian continent using available lithospheric architecture determined through seismic tomography and impose the inferred plate motion associated with this region. Our models incorporate updated peridotite melting and melt chemistry parameterisations that provide quantitative estimates of generated melt volume and composition. We find that plume-driven and shallow edge-driven melting processes, modulated by the lithospheric thickness of the Australian continent, combine to explain the observed volcanic record. Our preliminary results agree well with surface observations and provide further insight into the geodynamics of eastern Australia.

How to cite: Duvernay, T. and Davies, D. R.: 3-D Modelling of Plume-Lithosphere Interaction: The Cosgrove Track, Eastern Australia, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15229, https://doi.org/10.5194/egusphere-egu24-15229, 2024.

X2.64
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EGU24-17719
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ECS
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María García-Rodríguez, Cristina de Ignacio, David Orejana, Carlos Villaseca, João Mata, and Rita Caldeira

Sal is the oldest island of the Cape Verde archipelago, with magmatic activity starting around 25 Ma (Torres et al., 2010). Located to the northeast of the archipelago, it forms part of a north-south islands alignment and features intrusive bodies potentially representing the subvolcanic roots of exposed volcanic rocks. These intrusions, dated from ≈ 14 to 17 Ma (Torres et al., 2010) are intrusive into the Old Eruptive Complex, located in the central-western part of the island and mostly comprised by gabbro bodies, dyke swarms and several circular gabbro to monzonite complexes.

There are no previous detailed studies concerning mineral chemistry and crystallization conditions of these intrusions, which are a first step, together with precise geochronology, to correlate them with any of the different volcanic series occurring in Sal. In this work we present preliminary mineral chemistry, whole-rock geochemistry and radiogenic (Sr, Nd, Pb) isotope data of the circular complexes aiming to characterize their main features, magmatic evolution and mantle source composition.

The studied rocks range from gabbros to monzonites, sometimes displaying cumulate textures. The main mafic minerals present variable compositions: olivine chemistry ranges from Fo61-81 in gabbros to Fo39-49 in monzogabbros; clinopyroxene is classified as augite-diopside in all samples; amphibole is mainly kaersutite-pargasite-Mg-hastingsite and biotite-phlogopite Mg# is in the range 0.4-0.7. Plagioclase is bytownite-andesine (An30-86) in gabbros, whereas it is more sodic in monzogabbros and monzonites (An16-66), while nepheline (Ne70-86) turns more potassic from gabbros to monzonites. Alkali feldspar (Or20-98) only appears in monzogabros and monzonites. The main accessory phases are ilmenite/Ti-magnetite, chromite, ulvospinel, titanite and apatite.

Major and trace element chemistry points to a progressive evolution from mafic to intermediate types characterized by a linear decrease of MgO, TiO2, FeOT, CaO, Ni and Cr, and a gradual increase of SiO2, Al2O3, K2O, Na2O, Rb, Ba, Zr and Nb. These patterns suggest initial crystallization of mafic phases (olivine, clinopyroxene, ilmenite-magnetite) and calcic plagioclase. The intra-complexes positive correlation between strongly incompatible element pairs: U-Th, La-Ce and Nb-Ta, suggests the predominance of fractional crystallization within each circular complex.

The studied rocks display 87Sr/86Sr and 143Nd/144Nd initial ratios typical of some OIB having more Sr-radiogenic and Nd-unradiogenic compositions than the N-MORB. These signatures and the Pb isotope ratios are close to the FOZO composition, in an intermediate position between the HIMU and N-MORB mantle components. Small εNd and 206Pb/204Pb differences between the several circular complexes define two compositional groups, which implies slight heterogeneities in the mantle sources. These isotopic results support the association of Sal intrusive with the Cape Verde northern islands as no low Nd isotopic ratios have been found that could imply EM-1 enriched components, as those described by Torres et al. (2010) for some lavas.

Torres, P., Silva, L.C., Munhá, J., Caldeira, R., Mata, J., Tassinari, C. (2010): Petrology and geochemistry of lavas from Sal Island: Implications for the variability of the Cape Verde magmatism. Comunicaçoes Geológicas, 97: 35-62.

How to cite: García-Rodríguez, M., de Ignacio, C., Orejana, D., Villaseca, C., Mata, J., and Caldeira, R.: Petrology and geochemistry of alkaline Circular Complexes from Sal Island, Cape Verde archipelago., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17719, https://doi.org/10.5194/egusphere-egu24-17719, 2024.

X2.65
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EGU24-18227
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ECS
Alexander Rutson, Tiffany Barry, Stewart Fishwick, and Victoria Lane

Central East Asia has experienced intraplate volcanism over the past ~110 Myrs. The mechanism for this volcanism is enigmatic, with several potential causes put forward for the origin, including a mantle plume, edge convection, and lithospheric delamination. One of the big questions for the region is the role played by the long-term subducting systems of the Pacific/Izanagi and the Tethys Ocean(s). And secondarily, how much the volcanism is influenced by the lithospheric conditions and its changing thicknesses across the region.  

To recreate the conditions of mantle circulation and flow beneath Central East Asia, a mantle circulation model has been created using the fluid dynamics code ASPECT; the mantle circulation model is coupled with the plate reconstruction of Muller et al. (2019) for the surface conditions of the past 200 Myrs. To better understand the patterns of mantle flow, particles are emplaced into the model to track flow beneath the region, particularly around the subducted slabs. The mantle flow is compared to localities of intraplate volcanism across Central East Asia to assess whether any upwelling regions correlate with the spatial and temporal origins of the volcanism. Initial results show colder downwelling mantle from the surface boundary beneath Central East Asia at ~120-110 Ma, with warmer mantle upwelling into the region to replace it. The timing of this upwelling mantle coincides with the initiation of intraplate volcanism in the region; however, whether this results in the onset of intraplate volcanism in the region and the following 110 Myrs of intraplate volcanism is still being investigated. The mantle flow from the global models will then be used to inform the boundary conditions of a localised box model for Central East Asia. This model will be used to examine any potential effect of delamination beneath Central East Asia, and whether this model can explain any of the timings of intraplate volcanism formation. 

How to cite: Rutson, A., Barry, T., Fishwick, S., and Lane, V.: A geodynamic perspective on the formation of intraplate volcanism in Central East Asia, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-18227, https://doi.org/10.5194/egusphere-egu24-18227, 2024.

X2.66
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EGU24-12578
Lara M Kalnins, Amelia K Douglas, Benjamin E Cohen, J Godfrey Fitton, and Darren F Mark

Eastern Australia and the neighbouring Tasman and Coral Seas are home to extensive age-progressive volcanism spanning from ~55 Ma in the north to ~6 Ma in the south. This volcanism forms two offshore seamount trails, the Lord Howe and the Tasmantid Chains, as well as the onshore central volcanoes and leucitites of the East Australian Chain. The three volcanic chains are an average of just 500 km apart, erupted contemporaneously from 35-6 Ma, and share a common age-distance relationship, strongly suggesting a common source, most likely a deep-origin plume. However, they have erupted through lithosphere ranging from oceanic with well-developed seafloor spreading to drowned continental fragments to mainland Australia. How do these diverse settings influence the chemical and physical properties of the resulting mafic volcanism? The East Australian Chain has more fractionated mafic samples, reflecting more complex magmatic plumbing and longer magma residence times in the thick continental lithosphere. However, the most striking result is that the trace element and isotopic ratios remain remarkably similar across the three suites, showing little evidence of crustal or lithospheric assimilation affecting the mafic magmas. 

How to cite: Kalnins, L. M., Douglas, A. K., Cohen, B. E., Fitton, J. G., and Mark, D. F.: The influence of the lithosphere on deep-origin volcanism, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12578, https://doi.org/10.5194/egusphere-egu24-12578, 2024.

X2.67
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EGU24-19827
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Christian Mohn, Vibe Schourup-Kristensen, Janus Larsen, Franziska Schwarzkopf, Arne Biastoch, Inês Tojera, Miguel Souto, Manfred Kaufmann, Anna-Selma van der Kaaden, Karline Soetaert, and Dick van Oevelen

Seamounts and carbonate mounds are ubiquitous features of the global deep seascape. They often provide habitat for unique benthic species communities and support increased production and aggregation of phytoplankton, zooplankton, micronekton, and fish. Seamounts and carbonate mounds interact with the surrounding currents generating flow phenomena over a wide range of spatial and temporal scales including stable Taylor caps, energetic internal waves and turbulent mixing, all with the potential to enhance productivity, biomass, and biodiversity in an often food-limited deep-sea environment. We present hydrodynamic and ecological framework conditions at two contrasting topographic features in the North Atlantic, Great Meteor Seamount and Haas Mound. Great Meteor Seamount is of volcanic origin and one of the largest seamounts in the subtropical North Atlantic rising from 4200 m depth at the seafloor to a summit depth of 270 m. Great Meteor Seamount shows remarkable endemism in meiofaunal groups of copepods and nematodes. Haas Mound is one of the largest biogenic carbonate mounds of the Logachev mound province along the Southeast Rockall Bank in the Northeast Atlantic with a species rich benthic fauna dominated by the cold-water coral Desmophyllum pertusum (Lophelia pertusa). We used results from hydrodynamic models to identify the physical processes, which potentially support seamount and carbonate mound biodiversity. The models employ high-resolution local bathymetry, basin-scale lateral forcing and tidal forcing. Our model simulations provide a detailed three-dimensional picture of the fine-scale motions and physical processes, which potentially drive bio-physical connections such as particle retention and continuous or episodic food supply to benthic communities. 

How to cite: Mohn, C., Schourup-Kristensen, V., Larsen, J., Schwarzkopf, F., Biastoch, A., Tojera, I., Souto, M., Kaufmann, M., van der Kaaden, A.-S., Soetaert, K., and van Oevelen, D.: Seamounts and giant carbonate mounds drive bio-physical connections in the deep-sea: Two case studies from the North Atlantic., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-19827, https://doi.org/10.5194/egusphere-egu24-19827, 2024.

X2.68
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EGU24-6163
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ECS
Reconstructing oceanic plateau sequences and kinmatic analysis during the accretion process:insight from the Nuomuhongguole early Paleozoic accretionary complex in East Kunlun orogenic belt
(withdrawn)
Rutao Zang, Yunpeng Dong, Dengfeng He, and Shengsi Sun
X2.69
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EGU24-11882
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ECS
Petrogenesis and Significance of Volcanic Rocks of the Northern Songliao Basin: Constraints of Geochronology, Elements Geochemistry and Sr-Nd-Pb-Hf Isotopes
(withdrawn after no-show)
Yan Wu and Min Wang
X2.70
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EGU24-11610
Anthony Watts and Ingo Grevemeyer

The Great Meteor Seamount is a guyot and the largest seamount in the North Atlantic Ocean with an estimated volume of some 24,000 km3. Located ~1280 km west of Africa and ~720 km south of the Azores, the seamount forms part of a group of seamounts which include Hyeres, Irving, Cruiser, Plato, Atlantis, and Tyro. Previous dredged rock, magnetic anomaly lineation, and predicted hotspot track studies suggest the seamount is ~17 Myr in age, was emplaced on oceanic crust and lithosphere with a thermal age of ~68 Ma and is linked to the New England Seamount Chain. However, bathymetric, free-air gravity anomaly and geochemical data are inconsistent with these ages and such a tectonic setting: bathymetric data suggest a guyot depth of ~400 m which is deeper than expected (~187 m), gravity data suggest an effective elastic thickness, Te, of ~20 km which is lower than expected (~26 km) and geochemical data suggest a link, not to the New England Seamount Chain, but to the Azores Islands instead. To address these inconsistencies, we used legacy Ocean Bottom Hydrophone, free-air gravity anomaly and bathymetry data to reassess the seismic structure, Te, and tectonic evolution of Great Meteor Seamount and its neighbouring seamounts. We show the uppermost crustal structure of Great Meteor Seamount is characterised by a relatively low velocity volcano-clastic sediments (2.0-4.5 km/s) and extrusive lava (5.0-6.0 km/s) drape which overlies a relatively high P-wave velocity intrusive ‘core’ of 6.0-6.5 km/s. The lowermost crust, in contrast, is characterized by a 4-km-thick body of P-wave velocity 7.00-7.75 km/s intermediate in velocity between the crust and mantle, the base of which is at depths at ~16 km. This seismic structure has been verified by gravity modelling assuming a Gardner and Nafe-Drake relationship between P-wave velocity and density, but 3-D flexure modelling reveals that a Moho depth at ~16 km requires a low elastic thickness (Te ~10 km) which is inconsistent with the amplitude and wavelength of the free-air gravity anomaly and the relatively flat depth to the top of the oceanic crust beneath the flexural moats flanking the guyot ‘core’. We found that gravity and seismic data are consistent if the Te of flexed oceanic crust at Great Meteor Seamount is ~20 km and is underlain by a ~4-km-thick magmatic underplated body. In contrast, we found that the Irving, Cruiser, Plato, Atlantis, and Tyro seamounts are characterised by a best fit Te of ~10 km and no evidence of underplating. We discuss these findings here with respect to the guyot depth at Great Meteor, terrace depths at Plato, and the tectonic setting of Great Meteor and its neighbouring seamounts.

How to cite: Watts, A. and Grevemeyer, I.: Legacy seismic refraction and gravity anomaly data in the vicinity of Great Meteor Seamount and its implications for plate flexure , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11610, https://doi.org/10.5194/egusphere-egu24-11610, 2024.