Despite their importance, the tempo, magnitude, and physical controls of melt generation, transport, and emplacement in LIPs and hotspot systems remain incompletely constrained. This session seeks contributions that investigate the mechanisms driving temporal patterns in magmatism--from mantle melting dynamics and plume pulsations to melt migration, storage, and eruption--and how these processes propagate from depth to surface expressions such as lava piles, seaward-dipping reflectors, volcanic rifted margins, and hotspot island chains. We particularly encourage interdisciplinary studies combining high-resolution geochronology, stratigraphy, petrology, trace-element and isotopic geochemistry, geophysical imaging, numerical or analogue modelling, and environmental proxy records.
We also welcome contributions exploring the broader consequences of pulsed magmatism, including links to climate change, volatile and nutrient fluxes, ecosystem disruption or creation, island and seamount corridor dynamics, and biogeographic and macroevolutionary patterns. The goal of this session is to build a mechanistic, multiscale framework for the generation and temporality of hotspot and LIP magmatism, and to quantify its cascading effects on plate tectonics, Earth-surface systems, and life through geological time.
Throughout Earth's history, episodic Large Igneous Province emplacements coincide with remarkable environmental perturbations including mass extinction, global warming, and oceanic anoxia events. The causal mechanism for this association remains unclear. An exemplar is the temporal coincidence between the North Atlantic Igneous Province (NAIP) and the Paleocene-Eocene Thermal Maximum (PETM) global warming event. The NAIP was emplaced over a period of c. 10 million years, whereas the PETM onset spanned c. 10 thousand years. This discrepancy in pacing has motivated the hypothesis that NAIP-derived carbon-based greenhouse gas emissions slowly changed the background climate until a threshold was reached, triggering positive feedbacks that rapidly released additional non-volcanic carbon emissions that drove the PETM. Here, we address an alternative hypothesis: that thermal mantle plume pulsing caused a pulse of NAIP magma generation and consequently a pulse of greenhouse gas emissions on the timeframe of the PETM. To test this hypothesis, the PORO-CLIM experiment has generated an approximately 400 km long wide-angle seismic model of oceanic crust south of the Rockall Plateau, within the outer NAIP. Crustal thickness and composition along this profile can be interpreted as a tape-recording of asthenospheric mantle temperature throughout NAIP emplacement. Mantle temperature was cool during late Cretaceous continental break-up, increased through the Paleocene coincident with early NAIP activity, peaked near the Paleocene/Eocene boundary coincident with the most voluminous NAIP activity, and decreased through the early Eocene as NAIP activity waned. This temperature cycle supports a plume initiation model for the NAIP. Multiple thermal pulses are superimposed on the long-term temperature cycle. The crustal morphology of these pulses resembles the V-Shaped Ridges currently forming in oceanic crust south of Iceland, which are thought to reflect thermal pulsing of the modern Icelandic Mantle Plume. The biggest hot mantle pulse observed on the PORO-CLIM profile is associated with the PETM. The difference between the age of this pulse recorded here within the outer NAIP and its age recorded within the inner NAIP by kilometre-scale uplift of sedimentary basins shows that the pulse travelled rapidly within the asthenosphere from the centre to the edge of the NAIP. This pulse of hot, solid mantle travelled sufficiently rapidly to generate a pulse of NAIP magma by decompressional melting on the 10–100 thousand year timeframe of the PETM. Thus the PORO-CLIM experiment supports a model in which the NAIP supplied a substantial proportion of volcanic greenhouse gases that triggered the PETM. More generally, we propose that thermal plume pulsing is a key physical process that explains how relatively slow Large Igneous Province emplacements coincide with relatively rapid environmental perturbations.
How to cite: Knight, H., Jones, S. M., Hopper, J. R., Funck, T., and O'Reilly, B. M.: The PORO-CLIM experiment: Did the North Atlantic Igneous Province drive the Paleocene-Eocene Thermal Maximum?, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-11540, https://doi.org/10.5194/egusphere-egu26-11540, 2026.
Thermal pulsing is thought to be a characteristic process of major mantle convection cells. Seafloor features near Iceland, known as the "V-Shaped Ridges" (VSRs), may comprise the best record of thermal plume pulsing. However, a satisfactory test of this thermal plume pulsing model has been compromised by the lack of suitable geophysical and geochemical datasets from the VSRs. Here, we present the first full crustal seismic image of multiple complete VSR cycles. In 2024, the IMPULSE experiment acquired an approximately 400 km long profile that straddles the Reykjanes Ridge spreading axis and several V-Shaped Ridge/Trough cycles spanning over 18 million years. Traveltime picks for crustal and upper mantle refractions and PmP wide-angle Moho reflections were inverted using the TOMO2D software package to obtain crustal thickness as well as crustal and upper mantle seismic velocity. The results show crustal thickness variations that correlate with VSR geometry. They also reveal seismic velocity variations which indicate fluctuations in mineralogy of the lower crustal cumulates that correlate with the VSRs. Mid-ocean ridge basalts sampled by International Ocean Drilling Program Expedition 395 at five sites along the seismic profile show trace element variations that correlate with the VSRs. Significantly, we have imaged both conjugate flanks of the spreading axis along a plate spreading flowline. Comparison of conjugate crustal thickness and structure permits us to disentangle primary melt supply processes from asymmetric crustal accretion processes. The combined geophysical and geochemical dataset supports a model in which the VSRs form when thermal plume pulsing causes fluctuations in the volume and composition of magma supplied to the mid-oceanic ridge, and crustal accretion processes related to oblique spreading at variable rate then modify VSR morphology in different locations.
How to cite: Jones, S. M., Dhabaria, N., Henstock, T., and White, N.: The IMPULSE experiment: New oceanic crustal record of thermal plume pulsing of Earth’s strongest mantle plume, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-14092, https://doi.org/10.5194/egusphere-egu26-14092, 2026.
The magma plumbing system of large igneous provinces may include emplacement of voluminous sill complexes in sedimentary basins. Key examples include the North Atlantic Igneous Province (NAIP; c. 56 Ma), the Karoo-Ferrar province (c. 183 Ma), and the Siberian Traps province (c. 251 Ma). In these basins, thousands of kilometer-sized hydrothermal vent complexes are associated with the sill complexes. We have interpreted new and legacy 2D and 3D seismic data in the Vøring and Møre basins offshore Norway to characterize the sill and hydrothermal vent complexes in a 100,000 km2 large region. The upper part of one of the hydrothermal vent complexes, the Modgunn Vent, was cored by five boreholes during IODP Expedition 396 in 2021. Saucer-shaped sills and overlying domes at the Top Paleocene level characterize the Jolnir, Tulipan and Infinity sill complexes in the Møre Basin. In contrast, sill complexes in the Vøring Basin display more variable morphologies, including ponding thick sheets and transgressive sheets reflecting the variations in deep basin structure and type of host rocks. The extensive Vivel Sill in the Vigrid Syncline is locally more than 200 m thick in the deeper parts of the basin, with some domal-shaped geometries that crosscut the deep basin stratigraphy and layer-parallel planar geometries at shallow stratigraphic levels. The hydrothermal vent complexes are mainly present as pipe-like disruptive seismic anomalies above transgressive sill segments connecting the contact aureoles with crater- or eye-shaped upper parts of the vent complexes near the Top Paleocene reflection. Scientific and industry drilling samples document that the vent craters were infilled during earliest Eocene times, most likely related to sill emplacement during the Paleocene-Eocene Thermal Maximum (PETM). In conclusion, the current geometries of voluminous igneous sheet intrusions both reflect the pre-emplacement deep basin structure and post-emplacement structural deformation, whereas the contact metamorphic processes triggers pipe-like deformation and focused fluid flow during formation of hydrothermal vent complexes.
How to cite: Planke, S., Zastrozhnov, D., Lebedeva-Ivanova, N., Millett, J. M., Svensen, H. H., Abdelmalak, M. M., Faleide, J. I., Berndt, C., Bünz, S., Binde, C., Bischoff, A., Trulsvik, M., and Myklebust, R.: The structure, distribution and environmental implications of voluminous sill and hydrothermal vent complexes in the Vøring and Møre basins, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-23102, https://doi.org/10.5194/egusphere-egu26-23102, 2026.
Hydrothermal vent complexes are degassing structures that form in response to rapid volatile generation and release associated with igneous sill intrusions in sedimentary basins. They are discovered in numerous basins worldwide, originating from sills and contact aureoles and terminating at the paleosurface where they form up to 10 km wide craters. Field studies and numerical models have suggested that the venting processes were explosive, releasing aureole-derived gases, sedimentary pore fluids, and fragmented sedimentary rocks to the seafloor or land surface. However, ejecta deposits originating from hydrothermal vent complexes are poorly studied and hard to identify, hampering detailed reconstructions of vent formation and evolution. Here we report the characteristics of a possible ejecta deposit from Vøring Basin Hole U1570D drilled as part of IODP Expedition 396 in 2021. During core logging, an unusual layer was identified immediately overlaying the top Paleocene strata. This layer is about 2m thick, contains Apectodinium augustum dinocysts restricted to the Paleocene Eocene Thermal Maximum (PETM), and also yields abundant reworked Paleocene and Cretaceous microfossils. Moreover, the layer is characterized by rounded fragments of claystone, angular chert and quartz fragments, dolerite fragments, fresh and devitrified volcanic tephra, and a mixed groundmass of smectite-illite with diatoms and early diagenetic pyrite. Electron microprobe analyses document a bimodal tephra geochemistry, with both basaltic and rhyolitic compositions and morphologies indicating no or minor reworking. In the presentation we will discuss two possible formation scenarios for the layer, including 1) erosion from nearby marginal highs, and 2) ejecta deposit sourced from an explosive submarine eruption from a hydrothermal vent complex, mobilizing Cretaceous and Paleocene strata from the conduit zone. In any case, the bimodal tephra composition stresses the presence of an evolved igneous system in the Vøring Basin during the PETM, with a potential genetic link to a recently discovered Paleocene granite.
How to cite: Svensen, H. H., Tegner, C., Jolley, D. W., Brinkhuis, H., Nygaard, M. S., Jones, M. T., and Planke, S.: Petrographic and geochemical characteristics of a possible vent-related ejecta deposit at the Paleocene-Eocene boundary in the Vøring Basin, offshore Norway, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-16847, https://doi.org/10.5194/egusphere-egu26-16847, 2026.
Hotspot chains and Cretaceous large igneous provinces (LIPs) in the southern Pacific are spatially associated with the South Pacific Superswell and have been linked to the possible presence of a “superplume” in the deep South Pacific mantle, potentially rooted near the Pacific LLSVP at the core–mantle boundary. Compared with the long-lived, age-progressive Hawaiian-type chain, many South Pacific intraplate volcanic chains appear short-lived and/or discontinuous, which is inconsistent with key assumptions of the classical Wilson–Morgan hotspot hypothesis. Nevertheless, geophysical observations remain sparse, limiting our understanding of plate thermal evolution and the underlying mantle dynamics. To decipher the impact of Cretaceous magmatism and to further improve our understanding of the thermal evolution of oceanic plates, we constrained the lithospheric seismic structure using data recorded by ocean-bottom seismometer arrays. As part of the Pacific Array, an ongoing transnational collaboration, the Oldest-2 deployment was jointly carried out by research teams from Taiwan and Japan. We integrated Oldest-1 data to expand the spatial coverage across the oldest Pacific seafloor, sampling the Magellan Seamount and two adjacent Large Igneous Provinces, the East Mariana Basin and the Pigafetta Basin. We applied the ambient noise tomography method to constrain the three-dimensional isotropic and anisotropic shear-wave velocity structure of the oldest Pacific lithosphere. The resulting radial anisotropy exhibits distinct characteristics between the Magellan Seamount and the two adjacent LIPs. The seamount shows strong radial anisotropy from the crust down to ~30 km depth, indicating well-developed, horizontally oriented crystallized sills. In contrast, the LIPs exhibit negative radial anisotropy within the crust and uppermost mantle. We interpret this anisotropic signature as reflecting former magma conduits, where large volumes of magma were transported vertically from deeper sources to the surface over a relatively short timescale. These findings suggest that, although the seamounts and LIPs beneath the southern Pacific seafloor were likely formed by secondary magmatic sources, the oceanic plate has remained affected by these magmatic processes and continues to preserve clear seismic signatures of such activity, providing valuable observational constraints on the oceanic lithosphere–asthenosphere system.
How to cite: Chen, K.-X., Isse, T., Kawakatsu, H., Shiobara, H., Takeuchi, N., Sugioka, H., Utada, H., Kuo, B.-Y., Lin, P. P.-Y., Hung, S.-H., Chang, P.-Y., Yang, Y., Chi, W.-C., Kim, Y., Lee, S.-M., and Gung, Y.: Imprints of Cretaceous magmatism on the oldest Pacific lithosphere: evidence from seismic anisotropy, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-17771, https://doi.org/10.5194/egusphere-egu26-17771, 2026.
Basalts from the Western Ghats lava sequences of the ca. 66 Ma Deccan Large Igneous Province (LIP) display substantial geochemical variability from enriched, crust-like signatures in the Late Cretaceous Kalsubai and Lonavala Subgroup basalts (e.g., 87Sr/86Sri mainly 0.705-0.715) to more depleted, mantle-like signatures in the Early Paleogene Wai Subgroup basalts (generally, 87Sr/86Sri ca. 0.703-0.706). By contrast, Os isotopic compositions are relatively uniform throughout the Western Ghats stratigraphy (187Os/188Osi = 0.12 to 0.21). The lowest Os isotopic ratios are found in the Ambenali Formation of the Wai Subgroup (0.120) and may reflect a modest contribution from the subcontinental lithospheric mantle. Overall, the combined isotopic and trace-element data—particularly the Os isotopic signatures—indicate that assimilation of Proterozoic to Archean Indian crust was generally minimal (<3 wt.% of the parental magma) and did not exceed 8 wt.% in any of the analyzed samples. Comparable findings have been reported for other areas of the Deccan (Peters and Day, 2017) and other Phanerozoic LIPs. We therefore propose that the emplacement of LIPs as short-lived eruptive pulses, separated by relatively long hiatuses, limited sustained heating of the crust above its solidus and thus inhibited significant crustal contamination (Marzoli et al., 2026).
Marzoli, A., Reisberg, L., Capriolo, M., Callegaro, S., Renne, P. R., Chiaradia, M., Meyzen, C. M., Self, S., Vanderkluysen, L., Boscaini, A. (2026). Limited crustal contamination in large igneous province basalts: Sr-Nd-Pb-Os isotope evidence from the Western Ghats, Deccan Traps. Earth Planet. Sci. Lett. 678, 119847. doi: https://doi.org/10.1016/j.epsl.2026.119847.
How to cite: Callegaro, S., Marzoli, A., Reisberg, L., Capriolo, M., Renne, P. R., Chiaradia, M., Meyzen, C. M., Self, S., Vanderkluysen, L., and Boscaini, A.: Are Deccan basalts contaminated by the continental crust? , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-10981, https://doi.org/10.5194/egusphere-egu26-10981, 2026.
The emplacement of Large Igneous Provinces (LIPs) and subsequent volatile release are associated with catastrophic changes to the earth system and mass extinctions. LIP volatiles can be directly released through igneous degassing and/or indirectly released through metamorphic processes as carbon and sulfur bearing sediments are heated by intrusions and lava flows. Sediment derived carbon emission has been given consideration for its impact on warming (Heimdal et al., 2018; Svensen et al., 2018). Svensen et al (2018) found through modeling that Siberian Trap sill emplacement was predicted to have released 2.3 × 1016 moles of sedimentary C in just 0.7–1.2% of the Tunguska Basin, and modeling by Heimdal et al (2018) proposed that Central Atlantic Magmatic Province (CAMP) sills could cause 2.0 × 1018 moles C to be degassed from sediment through contact metamorphism in just two CAMP basins. While the metamorphic carbon production during LIP emplacement has been given attention metasedimentary sulfur emission has been largely ignored. One study, Yallup et al (2013), looks at both metamorphic carbon and metamorphic sulfur emission during LIP emplacement finding evidence of decarbonation and desulfurization substantially increasing the sulfur yield to the surface.
Aside from Yallup et al., (2013) metamorphic sulfur degassing is largely disregarded partly due to the broad assumption that sulfur must reach the stratosphere to drive sustained cooling. However, if the input of sulfur into the troposphere itself is sustained, this can extend the climatic cooling. Metamorphic sulfur degassing during LIP emplacement offers a mechanism for this type of prolonged cooling. We will begin by presenting thermodynamic modeling of sediment metamorphism in tangent with a simple carbon cycle and planetary energy balance model. Together these models show carbon and sulfur emissions from contact metamorphism could be sustained long enough to cause centennial scale sulfate aerosol cooling spikes of several kelvin superimposed on millennial scale warming from carbon dioxide emission. This suggests that metamorphic sulfur should be considered as a plausible driver of sustained cooling.
Further, we present sulfur and carbon geochemical data from a field test of metamorphic volatile emissions to verify modeled mechanisms using an observational approach. We use samples from the Sugar Grove dike, an Eocene basalt intruded into the Devonian Millboro black shale in West Virginia, as a well-exposed and accessible proxy for basaltic LIP intrusion. We find evidence of decreasing pyrite and increasing pyrrhotite concentrations in the shale approaching the dike as a potential indicator of sulfur release. We will also present isotopic data for pyrite and pyrrhotite sulfur, organic carbon, carbonate carbon, and carbonate oxygen. Together these results will constrain the magnitude of metamorphic sulfur release and test its viability as a mechanism for cooling before warming during LIP emplacement.
How to cite: Allman, L., Stewart, E., and Diamond, M.: Contact metamorphism and sulfur release during Large Igneous Provence emplacement, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-12753, https://doi.org/10.5194/egusphere-egu26-12753, 2026.
Volcanic basins play a central role in the exchange of volatiles between the lithosphere, hydrosphere, atmosphere and biosphere. The intrusion of magmas into sedimentary basins induces complex interactions between magma, sediments and fluids, profoundly modifying the biogeochemical cycles of carbon and sulphur. These phenomena are known to have contributed to major climatic and biological crises throughout Earth's history, but the mechanisms by which volatiles are partially trapped are still poorly understood.
This study (Cheviet et al. 2023; 2025) focuses on magma-sediment-fluid interaction processes and their consequences for the mobilisation and sequestration of carbon and sulphur in the Guaymas Basin (Gulf of California), a young system where basaltic sills were emplaced in unconsolidated sediments rich in organic matter and pore water. Three levels of interaction have been identified: (1) contact metamorphism, (2) magmatic contamination (3) late hydrothermal circulation. Taken together, these processes allow several hundred thousand tonnes of sulphur and large quantities of carbon to be stored locally. On a basin-wide scale, these interactions transform sills and their direct surroundings in volatile traps, modifying the global balance of greenhouse gases emitted during magmatic intrusions. This study shows that, contrary to the classic paradigm of complete degassing into the atmosphere, a significant proportion of volatiles can be sequestered in magmatic and metamorphic rocks over the long term. These magma-sediment-fluid processes will be studied at basin scale within the framework of the DEGAS project (ERC-2024-CoG).
Cheviet, A., Buatier, M., Choulet, F., Galerne, C., Riboulleau, A., Aiello, I., Marsaglia, K. M., and Höfig, T. W.: Contact metamorphic reactions and fluid–rock interactions related to magmatic sill intrusion in the Guaymas Basin, Eur. J. Mineral., 35, 987–1007, https://doi.org/10.5194/ejm-35-987-2023, 2023.
Cheviet A., Goncalves P., , Choulet F., Bach W., Riboulleau A., Vennemann T., Buatier M.: Carbon trapping during contact metamorphism in magmatic basins. Contributions to Mineralogy and Petrology https://doi.org/10.1007/s00410-025-02262-0, 2025.
ERC-2024-CoG “Deconvolving sources and sinks of carbon and sulfur in magmas to reconstruct DEGASsing from Large Igneous Provinces” https://doi.org/10.3030/101170872
How to cite: Cheviet, A., Buatier, M., Choulet, F., Galerne, C., Bach, W., and Callegaro, S.: Impact of magmatic activity and magma-sediment-fluid interactionson the transfer and sequestration of volatiles in the Guaymas Basin, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-12527, https://doi.org/10.5194/egusphere-egu26-12527, 2026.
Intrusive networks in continental rifts provide key constraints on the depth, lifespan, and organisation of magmatic plumbing systems. In the Oslo Rift, maenaite (microsyenite) and camptonite sills have long been interpreted as the earliest magmatic products and linked to specific early stress regimes, largely on the basis of Rb–Sr whole-rock and mineral ages of ~304–294 Ma (e.g. Sundvoll et al., 1992). Within this framework, the coexistence of felsic maenaite and phenocryst-rich camptonites has been used to infer tectonically controlled emplacement during a transition from compressional to extensional conditions at the onset of rifting (Larsen et al., 2008). However, U–Pb geochronology indicates prolonged intrusive magmatism in the Oslo Rift.
Here we present new high-precision U–Pb zircon CA-ID-TIMS ages from maenaite sills across the Oslo Rift. Maenaite sills at Jevnaker, central Oslo, and Slemmestad yield ages of 280–278 Ma. A younger maenaite sill at Byrud Emerald Mines yields ~271 Ma, and a trachyte sill in Alnabru yields ~265 Ma. These data define two principal sill-emplacement pulses at 282–278 Ma and ~273–270 Ma, followed by a later phase of intrusions at ~265 Ma, documenting a pulsed magma emplacement throughout most of the lifespan of the magmatic province.
The ~280 Ma pulse coincides with late plateau to early caldera-stage magmatism, including rhomb porphyry no. 11 (RP11), the Skrim Plutonic Complex, the B2 basalt, and the Ramnes Caldera (Corfu et al., 2024). The younger ~273–270 Ma pulse overlaps central volcano–caldera systems such as Drammen and Nittedal, broadly consistent with the stage-based evolution of the Oslo Rift outlined by Larsen et al. (2008). The revised chronology therefore removes the temporal basis for interpreting the maenaite sills as purely a product of an early, distinct tectonic regime. Instead, linking sill emplacement to more mature stages of rift evolution in an extensional to transtensional setting, when magma transport was apparently organised by mature plumbing systems also feeding central volcanoes.
Petrological observations support this interpretation. Although only maenaites are dated here, they occur together with camptonites, sometimes observed in the same sill, indicating a close relationship. The camptonites commonly contain very high proportions of amphibole and clinopyroxene phenocrysts and display cumulate textures, consistent with repeated recharge of deeper magma reservoirs. Preliminary thermobarometric calculations show amphibole and clinopyroxene crystallization in magma chambers at 20-30 km depth, in line with a model suggesting the presence of mafic cumulates remaining in the deeper crust, as indicated in geophysical data (Neumann et al., 1992).
Together, these results show that Oslo Rift sill emplacement records deep-rooted, long-lived magmatic systems pulsing throughout much of the lifespan of the volcanic province, providing new insight into how mantle and deep crustal processes govern magmatism in intracontinental rifts.
How to cite: Nipen, H., Callegaro, S., Svensen, H., Syversen, L. K., and Augland, L. E.: Sill intrusions in the Oslo Rift were pulsed: New evidence from CA-ID-TIMS U-Pb geochronology., EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-18922, https://doi.org/10.5194/egusphere-egu26-18922, 2026.
The interaction between mid-ocean ridges and mantle plumes (~1000 km scale) is a fundamental geodynamic process, generating complex spatio-temporal patterns of volcanism exemplified by the Galápagos platform and the prominent, en-echelon Wolf-Darwin lineaments. Unlike axial volcanism driven by pure extension, these off-axis features form in a regime where plate motion and deep plume flow create a dominant shear component. While such lineaments are characteristic of plume-ridge interaction (PRI) settings, the physical mechanisms governing their distinct spacing, orientation, and longevity remain enigmatic. Understanding these mechanisms is critical, as the resulting topographic heterogeneity governs seamount formation, which in turn profoundly influences ocean circulation and the distribution of deep-sea benthic habitats.
Here, we test the hypothesis that these lineaments result from melt localization instabilities driven by asthenospheric shear. We employ numerical models of viscous two-phase flow1 to simulate the deformation of pre-existing melt heterogeneities embedded in a porous background, treating the system as a localized shear box. We systematically vary the background porosity (φback= 0.01 - 0.05) and the melt pocket porosity (φmp = 0.04 - 0.08) to determine the conditions under which melt patches remain distinct—forming separate features like the Wolf-Darwin lineaments—versus coalescing into background flow channels.
Our results identify a hierarchy of length scales controlling melt structure evolution. Consistent with linear stability analysis and laboratory experiments, we observe an intrinsic background instability scale of λinst ≈ 0.1· δc (where δc is the compaction length). We find that the survival of pre-existing melt pockets follows a gradient dependent on the porosity contrast (φmp/φback): generally, pockets must exceed λinst by a factor of 2–4 to survive shear as intact features. Furthermore, we constrain the critical separation distance for maintaining distinct lineaments. Simulation results demonstrate that a minimum edge-to-edge separation of ≈ 1· δc is required to prevent hydraulic connectivity; below this threshold, pressure gradients drive adjacent patches to connect via background melt channels and coalesce.
To validate these scaling laws against natural systems, we apply a quantitative 2D continuous wavelet analysis2 to both simulation porosity fields and high-resolution bathymetry of the Galápagos Archipelago. This comparative spectral approach allows us to objectively quantify the dominant wavelengths and anisotropy of the observed lineaments without bias. By mapping the modeled stability regimes to the observed lineament spacing, we place constraints on the effective mantle viscosity and permeability structure required to preserve the Wolf-Darwin lineaments. These findings provide a mechanical framework for interpreting off-axis volcanism and define specific targets for future seafloor magnetotelluric and seismic anisotropy campaigns aimed at resolving lateral melt transport in PRI system.
1Zhongtian Zhang, & Jacob S. Jordan. (2021). Zenodo. https://doi.org/10.5281/zenodo.4460676
2Ungermann, J. (2025). JuWavelet (v01.03.00). Zenodo. https://doi.org/10.5281/zenodo.16962346
How to cite: Turino, V. and Mittal, T.: Stability of Melt Lineaments in Plume-Ridge Interaction Settings: Insights from Two-Phase Flow Models and Wavelet Analysis of the Galápagos Platform, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-13028, https://doi.org/10.5194/egusphere-egu26-13028, 2026.
Large igneous provinces (LIPs) are massive areas of predominantly mafic magmatism, often 105 -107 km2 in area with volumes greater than 105 km3, emplaced over a short period (1-5 m.y.). Field studies examining heat transfer processes acting within LIP sill complexes are relatively rare, despite the potential for contribution towards understanding LIP emplacement dynamics and overall interconnectivity of intrusive magmatic systems. This study uses paleomagnetic techniques (alternating field (AF) and thermal demagnetisation) to assess the magnitude of heat transfer associated with the Ferrar LIP sill complex, emplaced 183 Ma across the Transantarctic Mountains and through Tasmania and South Australia. Sampling was carried out through 3000 m of stratigraphy across four sites within the McMurdo Dry Valleys, South Victoria Land, Antarctica, in which 200 m thick Ferrar dolerite sills intrude the Beacon Supergroup sedimentary sequence. Our results quantify the vertical extent of magmatic heating from the Ferrar LIP sill complex, revealing an asymmetry in contact aureoles surrounding sills, which suggests contribution of differing heat transfer mechanisms above and below intrusions. Estimated contact aureole volumes also indicate increased heat flux with depth in the stratigraphy, suggesting more long-lived magma flux through deeper intrusions compared to those further up the sequence. This study has implications for understanding magma and heat fluxes during sill complex emplacement and the potential for these systems to liberate extinction-level volumes of carbon through crustal heating.
How to cite: Gilchrist, K., Muirhead, J., Nelson, F., Rowe, M., Rodrigues, S., Armstrong, Z., Patel, V., and Dempsey, D.: Ancient Antarctic Magmatism: Heat Flux within the Ferrar Large Igneous Province Sill Complex, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-1511, https://doi.org/10.5194/egusphere-egu26-1511, 2026.
The mechanical properties and rheology of the host rock in magmatic systems have a major control on the development of the plumbing system by affecting how magma propagates through the crust, via a range of brittle and non-brittle processes. In continental Large Igneous Provinces (LIPs), interaction between magma and carbon-rich layers (e.g. coal) is a fundamental process that has been shown to release large volumes of volatiles in the atmosphere, affecting global climate and sometimes triggering mass extinctions. While coal-magma interaction in continental LIPs has been well studied in the context of climate change and mass extinctions, few studies consider how this volatile release affects magma propagation and plumbing system development at the LIP scale. To infer how magma was emplaced in the crust, we analysed the morphologies of dikes associated with the 183 Ma Ferrar LIP emplaced in Beacon Supergroup sedimentary rocks using a range of structural measurements and field observations across three sites in the McMurdo Dry Valleys, Antarctica. A majority of dikes emplaced at ≥ 2 km paleodepth exhibit straight parallel margins, tapered tips, and stepped segments, indicative of brittle emplacement via tensile opening. However, we observe a noticeable transition to non-brittle behaviour at ≤ 1 km paleodepth, coinciding with dikes intersecting the late Permian Weller Coal Measures. Here, folding, faulting, and fluidisation of the host rock is commonly observed adjacent to dikes and is accompanied by a sudden shift in dike morphology and geometry. We hypothesise that local- and regional-scale heating of coal and carbonaceous shale resulted in large-scale volatile release, triggering host rock fluidisation, and ultimately promoting non-brittle modes of magma propagation at shallow paleodepths. Our findings support an evolving host rock rheology for LIPs intruding through volatile-rich sedimentary basins, which affects intrusion geometries, magma propagation processes, and the spatial and temporal development of LIP plumbing systems.
How to cite: Armstrong, Z., Muirhead, J., Gilchrist, K., Rodrigues, S., and Rowe, M.: Coal-magma interaction in the Ferrar Large Igneous Province, Antarctica: implications for magma propagation and plumbing system development, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-3184, https://doi.org/10.5194/egusphere-egu26-3184, 2026.
The Ontong Java Plateau (OJP) is thought to have formed through large-scale Cretaceous volcanism, however the process of the massive volcanism remains largely unknown. Shito et al. [2025] explored the ascent process of the thermochemical plume and its impact on the physicochemical properties of the preexisting lithosphere. Based on the high-frequency seismic wave analysis revealed that the internal structure of the lithosphere beneath the OJP is a hybrid structure comprising dike swarms that are superimposed on the laminar structure. Moreover, the lithosphere exhibits lower seismic wave velocities than normal oceanic lithosphere, suggesting that the lithospheric mantle was physicochemically altered by the intrusion of dike swarms filled with magma from a large-scale thermochemical plume.
This study employed two-dimensional tomography analysis to estimate lateral variations in dike density. The model parameter is relative energy reduction of So wave to Po wave and the data is Po and So wave envelope. As the first step, the two-dimensional tomography was performed under the assumption that the observed Po/So energy ratio is a simple integral value along the great circle path. The results revealed the presence of an area in the central part of the OJP where the reduction in So wave energy is significantly greater compared to Po waves. This suggests it corresponds to an area with high dike density and, also suggests the possibility that this location is the center of a massive eruption.
Future research aims to examine quantitative relationship between dike density and energy reduction of Po and So wave and the validity of the linearity, and to estimate the two-dimensional distribution of dike density using more appropriate methods.
How to cite: Shito, A. and Suetsugu, D.: Lateral variation in dike density within the lithosphere beneath the Ontong Java Plateau, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-3636, https://doi.org/10.5194/egusphere-egu26-3636, 2026.
Large igneous provinces (LIPs) are associated with the non-linear dynamics of deep mantle plume - lithosphere interactions, partial melting, volcanic emplacement and volatile emission on variable spatial and temporal scales. CO₂ emissions during such events are a major driver of mass extinction, the severity of which depends not only on the characteristics of the mantle plume, but also on the overlying lithosphere in which it is emplaced. The complex, multiscale processes connecting mantle-plume dynamics with surface volcanism, CO₂ outgassing, and the possible consequences for biological factors still needs further understanding.
To address this question, we use the thermomechanical numerical model I3ELVIS. This model incorporates mantle dynamic processes, such as partial melting and melt extraction. CO₂ is emitted in a simplified manner under the assumption of melt equilibrium and can be monitored over time and space. Our aim is to link deep Earth geodynamics with surface environmental and climatic consequences in order to provide a better, more comprehensive framework for understanding LIP events and quantifying their impact on mass extinctions.
Our preliminary results indicate that the intensity and temporal evolution of CO₂ outgassing depends on the geological setting and are not always synchronous with volcanic activity. Large igneous plume activity under oceanic crust results in single-peak rather than multi-peak outgassing, as observed in normal crustal and cratonic geological settings. Preliminary implications for climate and vegetation evolution are discussed.
How to cite: Ritter, S., Balázs, A., Rogger, J., Stemmler, D., and Gerya, T.: Numerical Simulation of CO₂ Emissions in Large Igneous Provinces and their Implication on Climate Evolution, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-3969, https://doi.org/10.5194/egusphere-egu26-3969, 2026.
Linking small-scale fracture processes to lithosphere-scale magma transport remains a core challenge in understanding the development of magmatic plumbing systems in Large Igneous Provinces (LIPs). In this study, we employ a two-dimensional Discrete Element Method (DEM) to investigate the coupled thermo-hydro-mechanical evolution of plumbing systems in the continental lithosphere. Using the MatDEM framework, we simulate fracture propagation, magma migration, and heat transfer from a magma chamber located at the lithosphere-asthenosphere boundary to the upper crust. Magma transport is modeled through a pore density flow approach, allowing dynamic coupling between pore pressure, temperature, and mechanical deformation of the host rocks. Scaling principles are applied to ensure mechanical and thermal similarity between numerical models and natural systems. The initial model shows that magma overpressure and thermal expansion generate radial fractures around the magma chamber, which progressively evolve into vertically connected magma pathways (i.e., dikes). We systematically examine the influence of layering structure, pre-existing faults, lower crustal strength, crustal thickness variations, magma viscosity, and magma overpressure on plumbing system development. The existence of horizontal weak zones or mechanical boundaries, such as the Moho and intra-crustal compositional boundaries will promote sill emplacement along these horizontal boundaries prior to renewed upward magma propagation. Steeply dipping faults further localize magma ascent and control geometry and number of sub-vertical conduits. A mechanically strong lower crust acts as a barrier to vertical magma ascent, favoring magma underplating and prolonged magma storage near the Moho. Crustal thickness gradients will drive magma migration toward the thinner crust. Increasing magma viscosity reduces magma flowability and limits the extent of fracture-controlled magma networks, whereas higher magma overpressure enhances fracture opening and results in a plumbing system with wider conduit width and larger spatial distribution. Our results fit well with geological and geophysical observations of LIPs. This DEM-based approach provides a bridge between small-scale fracture processes and the large-scale magma transport and emplacement in LIPs.
How to cite: Zhang, J., Wang, Q., Liu, C., and Liu, H.: Discrete Element Method (DEM) Simulation of Coupled Thermal, Mechanical and Melt Dynamics during Formation of Plumbing Systems of Large Igneous Provinces, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-6064, https://doi.org/10.5194/egusphere-egu26-6064, 2026.
Many hotspots worldwide display evidence of fluctuating magmatic activities that may be linked to time-dependent variations in melt production within mantle plumes. These periodicities are observed globally on Earth, ranging from 1 Myr to 20 Myr [Morrow and Mittelstaedt, 2021 ; Sokolov et al., 2025]. Remarkably, the Réunion hotspot exhibits short magmatic pulsations with a periodicity of ~400 kyr [Famin et al., in rev.]. Given the ~230 km separation between La Réunion and Mauritius, the synchronous short-period pulsations observed at the Réunion hotspot imply that they originate from deeper plume dynamics.
Understanding the physical controls behind these pulsations could establish links between mantle convection, plume dynamics, and surface volcanism. Previous studies suggest that plume behavior is sensitive to mantle rheology. Plume pulsations with periods of ~1-10 Myr have indeed been reported in numerical experiments and can stem from thermochemical instabilities due to the interaction of plumes with small-scale convection in the asthenosphere [Ballmer et al., 2009], thermal instabilities in sufficiently vigorous convection (Rayleigh number > 5×10⁶), buoyancy changes due to mineralogical phase transitions [Trubitsyn and Evseev, 2018], horizontal shearing caused by plate motions over an asthenosphere dominated by dislocation creep, leading to unstable tilted plume conduits [Neuharth and Mittelstaedt, 2023].
Here, we seek to investigate how mantle rheology can favour short-period pulses of plume activity and aim to identify the core physical mechanisms that control plume dynamics. We thus run 3D regional convection models in spherical cap geometry with plate-like behavior (viscoplastic rheology) at the surface using the StagYY code [Tackley, 2000]. We developed an automated algorithm to detect and track plumes in space and time, by defining plumes as the highest percentiles of the upwards vertical advective heat transport . The morphology and dynamics of plumes are then quantified using various parameters such as the buoyancy flux, heat flux, angle of inclination, along with their associated uncertainties. Our study explores the effects of surface yield stress (ranging 10-100 MPa), radiogenic heat production (3-15 pW/kg), a 30 to 100 fold viscosity jump at the transition zone, and of compressibility and phase transitions (especially the post-spinel transition at ~660 km depth that works as an accelerator of upwellings plumes and thus favors dynamic instabilities [Faccenda and Dal ZIlio 2016]) on plume dynamics as well as on plate tectonics. We aim to understand how these parameters control the generation of periodic activity and short-period term plume pulses and ultimately to estimate melt production variations at the surface in order to compare it with geological observations of magmatic products at the Réunion hotspot. Preliminary results indicate that surface yield stress and radiogenic heat production primarily affect plate tectonics, whereas a viscosity jump across the transition zone promotes periodic (~2 Myr) plume behavior.
How to cite: Koessler, A., Arnould, M., Perrillat, J.-P., and Famin, V.: Influence of Mantle Rheology on Plume Dynamics and Periodicities, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-19698, https://doi.org/10.5194/egusphere-egu26-19698, 2026.
How to cite: Lisica, K., Mark, D., and Barfod, D.: Quantifying mantle carbon fluxes during NAIP emplacement using trace element proxies and high-precision Ar–Ar geochronology , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-7939, https://doi.org/10.5194/egusphere-egu26-7939, 2026.
Intra-plate volcanism is commonly attributed to mantle plumes originating from deep-seated therm0-chemical anomalies that rise buoyantly through the mantle and puncture the overlying lithosphere. These long-lived magmatic systems can persist for tens of millions of years, producing age-progressive volcanic chains and, in some cases, interacting with mid-ocean ridges to generate off-axis volcanism. The Rodrigues Ridge, and more generally the Mascarene Islands in the Indian Ocean have traditionally been interpreted within this framework as the result of interaction between the Central Indian Ridge and the Réunion hotspot. Here, we present a new geochemical and geochronological investigation of volcanic rocks from Rodrigues Island, the subaerial expression of the Rodrigues Ridge, which challenges this classical model. Compared with published data from the Mascarene islands, our major, trace element and Sr-Nd-Pb isotopic analyses reveal systematic deviations from compositions expected for simple mixing between depleted mid-ocean ridge mantle and Réunion plume-derived melts. Instead, Rodrigues subaerial lavas, along with the intermediate and younger volcanic series of Mauritius Island; record the contribution of a third, geochemically distinct mantle source whose signature lies in the focus zone (FOZO) of Ocean Island Basalts isotopic compositions. This additional component requires the involvement of material derived from another deep mantle source. The most suitable candidate providing this plume-related material is the Mascarene Basin asthenospheric reservoir (MBAR), a low shear velocity zone in the asthenosphere beneath the Mascarene Basin identified by seismic tomographies described in Barruol et al. (2019). Moreover, on-axis volcanism in the Central Indian Ridge —and thus recent— have already been linked to the influence of the MBAR (Vincent et al., 2024). K-Ar geochronology combined with geochemistry allows us to constrain the timing of its contribution to the magmatism of the western Indian Ocean to the last ~4 million years. These results highlight the complexity of mantle plume–ridge interactions and suggest that the Indian Ocean upper mantle is fed by multiple plume sources whose contributions may overlap in space and time. Our study emphasizes the need to reconsider the upper mantle architecture beneath off-axis volcanic ridges and sheds light on the dynamics of plume dispersal within the asthenosphere.
How to cite: Seghi, J., Nauret, F., Famin, V., Quidelleur, X., Gourbet, L., Révillon, S., and Arnould, M.: A New mantle source contributing to volcanism in the Indian Ocean, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-14098, https://doi.org/10.5194/egusphere-egu26-14098, 2026.
Large Igneous Provinces (LIP) emplacement is commonly associated with severe environmental change. A primary way LIPs affect the environment is via the emission of climatically active gases, such as carbon (CO2, CH4) and sulfur (SO2, SO4 aerosol). The flux and tempo of these gas emissions control the effect they have on the environment, with different feedback effects dominating depending on emission tempos. Hence, estimates of LIP gas emissions at high temporal resolution are required to constrain the potential environmental impacts of a specific LIP. However, complex LIP chronostratigraphy and non-eruptive degassing make these estimates challenging.
Volcanic gas emissions are the main natural source of mercury to the environment. Increases in mercury concentration in sedimentary archives have thus been commonly used as a qualitative indicator of LIP activity. Our recent work has expanded this tool to quantitative reconstruction of volcanic gas fluxes. This technique requires understanding the size and rate of mercury emissions that correspond to an observed change in sedimentary records. However, a critical issue is that mercury records sometimes exhibit different patterns within the same time interval, complicating interpretation.
We use our understanding of the mercury cycle as represented by environmental mercury box models to evaluate several questions: A) What size/duration of eruptions are resolvable in sedimentary mercury records? Modern large explosive eruptions are rarely observed, whereas LIPs are. What are the limits? B) How do mercury records vary between different environments (e.g., terrestrial, coastal marine, deep marine settings)? C) Can we understand spatial and temporal changes in mercury deposition as a function of environmental conditions (e.g., regional riverine flux and long-term trends in volcanic activity)?
To answer these questions, we have developed several new tools. First, we adapt an existing environmental mercury box model to paleoenvironmental conditions, using parameters from continental hydrological models and background mid-ocean ridge and subduction zone volcanic activity. This model is used to simulate mercury deposition in different environmental settings for a variety of eruption (Hg emission event) rates and durations.
Then, we use a novel Bayesian inversion framework to analyze these results with published Hg records across multiple time periods and depositional environments, to test whether different coeval records are consistent with the same underlying forcing. We find that our model results, accounting for sediment accumulation rate and sampling resolution, effectively predict enrichment patterns across environmental settings, supporting the use of mercury records as a quantitative proxy. Additionally, the geologically short lifetime of mercury in the surface environment makes results highly sensitive to sediment accumulation rate and to volcanic pulse duration - e.g., short (<~100 year) pulses are not likely to be distinguishable from background variability in many sedimentary environments.
How to cite: Fendley, I. and Neilson, O.: Quantitative Reconstructions of Large Igneous Province Gas Emissions Using Mercury Chemostratigraphy , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-15423, https://doi.org/10.5194/egusphere-egu26-15423, 2026.
