John Millett

• Tegner, C.; Guo, P.; Chatterjee, S.; Lambart, S.; Jones, Morgan Thomas & Planke, Sverre [Show all 27 contributors for this article] (2026). A whole rock geochemical dataset for magmatic rocks drilled on the mid-Norwegian margin. Scientific Data. 13. doi: 10.1038/s41597-026-07073-x. Full text in Research Archive Show summary

  The mid-Norwegian margin is one of the best studied volcanic rifted margins on Earth. Geophysical investigations have demonstrated the presence of well-developed inner and outer Seaward Dipping Reflectors (SDRs), landward flows, lava deltas, marginal highs, volcanic centers, ash layers, and sill complexes. These features have been proven to consist of magmatic rocks through the international Deep Sea Drilling Program (DSDP Leg 38, 1974), Ocean Drilling Program (ODP Leg 104, 1985), International Ocean Discovery Program (IODP Expedition 396, 2021), and commercial drilling. A total of fifteen drill cores penetrated magmatic rocks that formed between 57 and 50 million years ago (Ma). Here we provide (i) new ( n =  224) major and trace element compositions obtained by X-ray fluorescence (XRF), inductively-coupled plasma mass spectrometry (ICP-MS), and inductively-coupled optical emission spectrometry (ICP–OES) on whole rock powders of magmatic rocks for IODP Exp. 396 ( n  = 119), ODP Exp. 104 ( n =  79), DSDP Exp. 38 ( n  = 24); and (ii) a compilation of all new and published data for magmatic rocks in the fifteen drill cores ( n  = 563). Portable X-ray fluorescence (pXRF) data ( n  = 381) for the IODP Exp. 396 cores are also reported. These datasets provide a resource for examining the origin of magmatism associated with continental breakup and rifted margin formation, particularly the formation of excess magmatism compared to normal mid-oceanic spreading ridges, mantle-crust interaction, and the linkage of magmatism to global hyperthermal events on Earth’s surface.

• Morris, Richard Ashley; Lambart, Sarah; Zarikian, Carlos A. Alvarez; Millett, John; Jones, Morgan Thomas & Planke, Sverre [Show all 16 contributors for this article] (2026). Recommendations for using core X-ray fluorescence data on basaltic rock as a tool to assess compositional variability. Scientific Drilling. ISSN 1816-8957. 35, p. 21–37. doi: 10.5194/sd-35-21-2026. Full text in Research Archive Show summary

  Portable and core-scanning X-ray fluorescence (XRF) instruments have become increasingly utilized in making rapid, non-destructive chemical characterizations with high spatial resolution on a range of materials. Since basaltic cores are often highly fractured and uneven, portable XRF (pXRF) is preferred to conduct discrete chemical analyses. However, in this case, the user must select the location for each analysis, which can lead to biased datasets. Alternatively, XRF core-scanning (XRF-cs) instruments take a series of measurements along a section of core, increasing the number of analyses and, therefore, eliminating some of the bias introduced by discrete analyses conducted with a pXRF. The XRF-cs does, however, still require a flat sampling surface along the core that does not include void spaces, making rigid, vesicular, and often cracked basalts suboptimal targets. We collected 797 XRF-cs measurements on three basaltic cores collected during the International Ocean Discovery Program Expedition 396 to evaluate how effectively an XRF core scanner can build large, chemically representative datasets. We developed a method for filtering XRF-cs measurements and calibrated the data using discrete calibrated pXRF analyses and compared the XRF-cs data to pXRF and conventional bulk-rock data using various immobile (e.g., Al, Ti, Zr, Ni, Mn, Zn) and mobile (e.g., K, Ca, Sr) elements. The comparison between datasets shows that (1) the XRF-cs data reproduce trends observed by pXRF and conventional bulk-rock data at both the regional scale and the core scale, and (2) in some cases, the higher spatial resolution of the XRF-cs data reveals geochemical variations that are otherwise obscured using discrete analyses. The workflow outlined by this study can be used to select samples for future studies by efficiently providing reliable geochemical data for characterizing new and legacy hard-rock cores.

• Zastrozhnov, Dmitrii; Zastrozhnov, Dmitry; Millett, John; Millett, John M.; Planke, Sverre & Polteau, Stéphane [Show all 18 contributors for this article] (2026). Polymetallic nodules offshore NE Greenland: links to Fram Strait opening and local hydrothermal activity. Sedimentary Geology. ISSN 0037-0738. 495, p. 107033–107033. doi: 10.1016/j.sedgeo.2026.107033. Full text in Research Archive Show summary

  This study presents the first documentation and analysis of polymetallic Fe–Mn seafloor nodules from offshore Northeast Greenland. Samples were collected from three sites by dredging and gravity coring along the slopes of both the outer and transform margin highs. The morphology, petrography, and whole-rock geochemistry of twenty-four nodules were determined. 10Be/9Be and (U–Th)/He dating were undertaken for representative samples to constrain the time of formation. Two nodule groups were identified in all studied sampling sites. Group 1 (n = 19) are light banded, primarily hydrogenetic nodules with notable enrichments in Mn and Fe, as well as several trace elements including rare earth elements (REE), V, Co, and Y. They have geochemical and textural similarities to Fe–Mn deposits from the Arctic Basin. 10Be/9Be age estimates suggest that growth initiated around 13,5 Ma, shortly after the opening of the Fram Strait, which influence deep-water circulation and inflow of nutrient-rich Arctic waters onto the NE Greenland shelf. Group 2 nodules (n = 5) are dense with high Fe (up to 64 wt% Fe2O3), low Mn content and little to no enrichment in trace elements and REEs. They are interpreted as hydrothermal in origin, with preliminary (U–Th)/He ages suggesting Quaternary formation under weak, diffuse fluid circulation in near-bottom environments of uncertain source. This study expands our understanding of seafloor mineralization in the Arctic–North Atlantic gateway, revealing that on the NE Greenland shelf this process reflects a long-term interplay between tectonic evolution, ocean circulation, and fluid-driven alteration.

• Cunningham, Emily H.; Lambart, Sarah; Guo, Pengyuan; Chatterjee, Sayantani; Tegner, Christian Maughan & Hartley, Autumn [Show all 25 contributors for this article] (2026). Evolution of the Source Mineralogy and Lithospheric Controls on Magmatism During the Northeast Atlantic Continental Breakup. Geochemistry Geophysics Geosystems. 27(2). doi: 10.1029/2025gc012556. Full text in Research Archive Show summary

  The mid‐Norwegian Margin, part of the North Atlantic Igneous Province (NAIP), is a well‐studied volcanic rifted margin formed during the breakup between Greenland and Eurasia ∼56 Ma, with the largest accumulation of magmatic material hosted by the Vøring Margin section. Despite extensive study in the area, the main controls on magmatic productivity during continental breakup remain debated. To constrain the drivers of breakup magmatism, we developed an inverse Monte Carlo statistical melting model that infers source mineralogy from basalt chemistry. When applied to basalts recently recovered on the Vøring Margin, our results reveal a clear shift in source mineralogy during rifting, with peak magmatism coinciding with clinopyroxene enrichment, despite mantle potential temperatures likely being capped below 1500°C. We also establish that, while the proto‐Iceland mantle plume played a role during the emplacement of the NAIP, the main driver for the continental breakup magmatism is lithospheric thinning as a consequence of continent breakup. This study provides new insights into the magmatic and geodynamic evolution of the mid‐Norwegian Margin, emphasizing the role of lithospheric refertilization in driving breakup magmatism.

• Polteau, Stéphane; Smalley, P. Craig; Devegowda, Vani N.; Johansen, Ingar; Millett, John & Rosenqvist, Marija Plahter [Show all 8 contributors for this article] (2026). Well-connected basalt sequences as potential reservoirs for large-scale carbon sequestration revealed by strontium isotopes. Communications Earth & Environment. 7(1). doi: 10.1038/s43247-025-03020-7. Full text in Research Archive Show summary

  Abstract Permanent storage of gigatons of carbon in basalt requires thick, uncompartmentalized sequences that allow lateral dissipation of CO 2 away from injection sites. Here we assess the presence of flow barriers by evaluating the variations in 87 Sr/ 86 Sr patterns in pore water, a method used extensively in sedimentary successions. Present-day pore water 87 Sr/ 86 Sr was measured from residual salts in core samples, while past water compositions were reconstructed from carbonate cements of different ages. We reveal smooth and uninterrupted trends in strontium isotopes through a 100 m thick basalt section indicating a common fluid reservoir unaffected by low-permeability massive lava flow interiors. The data further indicate that unconsolidated overburden sediments act as a good seal preventing seawater to mix with in situ pore water, and buoyant supercritical CO 2 to leak. Finally, basaltic sequences form viable targets for CO 2 storage and suggests that fractures may bypass low-permeability units to create a well-connected reservoir system.

• Fornero, S. A.; Millett, John; Jesus, C. M. de; Lima, E. F. de; Marins, G. M. & Pereira, N. F. [Show all 7 contributors for this article] (2025). Application of borehole images in the characterization of volcanic paleoenvironments with implications for the exploration of hydrocarbons in Brazilian basins. Shiyou kantan yu kaifa. ISSN 1000-0747. 52(3), p. 692–714. doi: 10.11698/PED.20240658. Full text in Research Archive
• Betlem, Peter; Rosenqvist, Marija Plahter; Millett, John; Griffiths, Luke; Filina, Irina & Park, Joonsang [Show all 9 contributors for this article] (2025). Fluid flow behaviour in vesicular basalt samples from the Skoll High, Vøring Margin. Geomechanics and Geophysics for Geo-Energy and Geo-Resources. ISSN 2363-8419. 12(1). doi: 10.1007/s40948-025-01080-9. Full text in Research Archive Show summary

  Abstract This study presents the fluid flow testing results of 32 lava flow samples recovered from IODP Sites U1571/U1572 (145–315 mbsf) on the Skoll High, Vøring Margin. Few past studies have investigated the mid-Norwegian margin’s basalt reservoir and flow properties. Even fewer implement subsurface-like conditions to explore in-situ fluid flow and the possible response to changing pore fluids during injection. These aspects are critical for large-scale carbon sequestration. In this study, hydraulic properties including porosity and permeability were measured at ambient conditions for all samples along with multi-stress, multi-fluid core flooding experiments on a representative sample enclosed in an X-ray µCT scanner. Petrographic observations reveal varying degrees of alteration with secondary clays, including smectite, commonly lining pores and vesicles. He-porosities (4.2–45.6%) fall mostly below the theoretical percolation threshold of ~ 30% for randomly distributed spherical pores. Klinkenberg-corrected nitrogen-gas permeability (0.0038–361.9 mD) shows weak correlation to porosity and no apparent depth dependence. Further, brine permeability is four orders of magnitude lower than gas permeability, with no notable flow reduction during injection of CO 2 . Rather than being stress-dependent, we argue that brine-induced swelling significantly reduced the accessibility of microstructural elements to fluids. The findings urge caution when using literature-reported, ambient gas measurements for basalts with similar levels of alteration as they may not accurately reflect in-situ fluid flow properties. Low matrix permeability of the moderately to highly altered vesicular basalts and prevalence of swelling clays may, without major contributions from fractures, limit the injectivity potential into the basaltic lava flows on the Skoll High, Vøring Margin.

• Nygaard, Madeleine Skov; Planke, Sverre; Zastrozhnov, Dmitry; Midtkandal, Ivar; Huismans, Ritske Sipke & Faleide, Jan Inge [Show all 13 contributors for this article] (2025). A tectonostratigraphic interpretation of the Mimir High through seismic-borehole tie: New insights into the Paleogene evolution of the Vøring Transform Margin. SEG technical program expanded abstracts. doi: 10.1190/image2025-4307795.1. Full text in Research Archive Show summary

  The Mimir High is a structural high along the Vøring Transform Margin (VTM), offshore Mid-Norway, having excellent coverage of high-resolution seismic 2D and 3D data and borehole data from five wells drilled during the International Ocean Discovery Program (IODP) Expedition 396. The Mimir High developed through rift tectonics and thermal uplift that resulted in a transition through different paleoenvironments from shallow marine to coastal or subaerial and finally marine again.

View all works in NVA

• Polteau, Stephane; Smalley, P. Craig; Devegowda, Vani; Millett, John; Rosenqvist, Marija Plahter & Abdelmalak, Mohamed Mansour [Show all 8 contributors for this article] (2026). Well-connected basalt sequences as potential reservoirs for large-scale carbon sequestration revealed by strontium isotopes. doi: https:/www.egu26.eu/. Full text in Research Archive Show summary

  Basalt complexes can cover hundreds to thousands of km2 and be several km thick; with an estimated global capacity of 40 Tt for carbon storage, they represent a solution for the large-scale injection of CO2 to reach the 2050 emission targets. However, the hydraulic conductivity of basalt sequences is difficult to predict because it has never been the focus in basalt research. In this contribution, we evaluate for the first time the vertical fluid connectivity of a basalt sequence using the Sr isotope composition of pore waters, sampled using the strontium residual salt analysis (SrRSA) method. Thirty seven samples were collected in the U1571A borehole (IODP Expedition 396 on the Skoll High, offshore Mid-Norway). Sampling of the well targeted the most representative lithologies in the core, and hence included vesicular and tight basalt. The SrRSA method measures the 87Sr/86Sr ratio in the salt residue that precipitated in the pores of core samples after the pore water evaporated, and the value measured in the laboratory should accurately reflect that of the in situ pore water. However, since the well was drilled using seawater with barite and sepiolite additives, each sample was washed in de-ionized water to reduce potential contamination. The samples were subsequently dried, crushed, the salts were leached, the leachate filtered, and the strontium analyzed using a MC-ICPS. The results show that the Sr concentrations are very low: 1-35 ppb in vesicular basalt samples and up to 2 ppb in tight basalt samples. The 87Sr/86Sr ratio of the vesicular basalt varies little away from the average value of 0.7085, while the values of tight basalts show more variability with an average of 0.7093. The SrRSA pattern vs. depth for the vesicular basalt samples is smooth, indicating limited contamination from drilling fluids, and further suggesting a good vertical connectivity. On the other hand, the pattern of the tight basalts is shifted towards heavier values similar to modern seawater, suggesting the SrRSA for these samples to be contaminated by the drilling fluids. In addition to the residual salts, we are currently analyzing the 87Sr/86Sr in carbonate vesicles and in basalt, which together represent the three main reservoirs of strontium in the samples. These additional results should help us constrain the source of the strontium in the pore system (i.e.: external, flowing or diffusing through the sequence). These results further show that the fluid connectivity of basalt sequences can be characterized using the SrRSA method by focusing the analyses on vesicular basalt samples. Finaly, this study will provide additional constrains to follow-up numerical models simulating the injectivity and capacity of intra- and inter-basalt reservoir units.

• Polteau, Stephane; Smalley, P. Craig; Devegowda, Vani; Johansen, Ingar; Millett, John & Rosenqvist, Marija Plahter [Show all 8 contributors for this article] (2026). Fluid connectivity and evolution of pore water in breakup basalt offshore mid-Norway with implications for CO2 storage. doi: https:/ngwm2026.fi/. Full text in Research Archive Show summary

  Basalt complexes can cover thousands of square kilometres and be several kilometres thick. With an estimated global carbon storage capacity of 40 Tt they represent a possible solution to reach the 2050 emission targets. However, the injection of gigatons of CO2 into basaltic formations requires a thick reservoir system lacking barriers to lateral fluid flow for the CO2 to dissipate away from injection points. In this contribution, we evaluate for the first time the vertical fluid connectivity of a basalt sequence using the Sr isotope composition of pore waters, sampled using the strontium residual salt analysis (SrRSA) method. Thirty-seven samples were collected in the U1571A borehole (IODP Expedition 396 on the Skoll High, offshore mid-Norway). Sampling of the well targeted the most representative lithologies and hence included vesicular basalt and massive flow interiors. The SrRSA method measures the 87Sr/86Sr ratio in the salt residue that precipitated in the pores of core samples after the pore water evaporated, and the value measured in the laboratory should accurately reflect that of the in-situ pore water. In addition to present-day pore water from the residual salts, the 87Sr/86Sr of past water compositions were reconstructed from carbonate cements of different ages. We reveal smooth and uninterrupted trends in strontium isotopes through a 100 m thick basalt section indicating a common fluid reservoir unaffected by the low-permeability massive lava flow interiors. The data further indicate that the unconsolidated overburden sediments act as a good seal preventing seawater to mix with in situ porewater and may prevent CO2 leakage to the surface for buoyant supercritical CO2 injection scenarios. This study supports the premise that basaltic sequences form viable targets for CO2 storage and suggests that fractures may bypass low-permeability units to create a well-connected reservoir system. Finally, the 87Sr/86Sr method is demonstrably useful in basalts, and warrants being included routinely in evaluating thick basalt sequences for large-scale CO2 storage.

• Polteau, Stephane; Smalley, P. Craig; Devegowda, Vani N.; Johansen, Ingar; Millett, John & Rosenqvist, Marija Plahter [Show all 8 contributors for this article] (2026). Fluid connectivity and evolution of pore water in breakup basalt offshore mid-Norway with implications for CO2 storage. doi: https:/ngwm2026.fi/conference-programme. Full text in Research Archive
• Tugend, Julie; Mohn, Geoffroy; Kusznir, Nick; Planke, Sverre; Berndt, Christian & Manton, Ben [Show all 8 contributors for this article] (2025). Palaeobathymetry of the Mid-Norwegian volcanic margin during continental breakup and paleoclimate implications. doi: 10.5194/egusphere-egu24-11873. Full text in Research Archive Show summary

  The Mid-Norwegian volcanic rifted margin and its NE-Greenland conjugate formed in relation to continental breakup in the latest Palaeocene to earliest Eocene during the emplacement of the North Atlantic Igneous Province (NAIP). The development of the NAIP and opening of the North Atlantic occurred contemporaneous to the Paleocene Eocene Thermal Maximum (PETM) which corresponded to a rapid 5-6 °C global warming episode.The cause of this rapid global warming, explored as part of IODP Expedition 396, is thought to relate to the thermogenic gases released to the atmosphere via thousands of hydrothermal vents. The thermogenic gases were produced by contact metamorphism of carbon-rich sediments during widespread sill emplacement from the NAIP. The potential of hydrothermally-released greenhouse gases to influence climate depends strongly on the water depth at which they get released. Unless it is released in a shallow marine environment most methane will be oxidized before it reaches the atmosphere.Early results from IODP Expedition 396 have documented that at least one of the Mid-Norwegian hydrothermal vents was emplaced in shallow marine to potentially sub-aerial conditions. The aim of this contribution is to constrain further the paleo-water depth at which hydrothermal vents formed along the other parts of the mid-Norwegian volcanic rifted margin. This study focuses on an integrated workflow of quantitative geophysical and geodynamic analyses calibrated by new IODP drilling results and structural and stratigraphic observations. We use a 3D flexural-backstripping, decompaction and reverse thermal subsidence modelling to predict the palaeobathymetry and palaeostructure at keys stages of the syn- to post-breakup evolution that can be compared with palaeo-water depths estimated from biostratigraphic data. Results provide new constraints on the paleobathymetry of hydrothermal vent complexes required to confirm whether the global warming recorded by the PETM was triggered by the magma-rich continental breakup leading to the opening of the northeast Atlantic Ocean. 

• Millett, John; Planke, Sverre; Jolley, David; Berndt, Christian; Betlem, Peter & Rosenqvist, Marija Plahter [Show all 9 contributors for this article] (2025). Characterizing lava flows in offshore North Atlantic boreholes: a review with implications for basalt carbon storage. doi: 10.5194/egusphere-egu24-12383. Full text in Research Archive Show summary

  Widespread and large-scale volcanism associated with the North Atlantic Igneous Province (NAIP) erupted during the Paleocene and Early Eocene and covers vast regions of the conjugate North Atlantic rifted margins. The majority of the preserved volume occurs in the offshore sequences of the continental shelves of Greenland, the Faroe Islands, UK, and Norway. These vast mafic igneous rock volumes in the offshore NAIP have been proposed as a potential area for permanent CO2 storage. However, a wide range of factors influence the suitability of mafic rock masses to act as fluid reservoirs including perhaps most importantly the volcanic facies (and associated pore structure, permeability, and distribution), along with alteration state, fracturing, and reactivity. In this contribution we focus on assessing the nature, distribution, and reservoir potential of sub-aerial lava flows from available borehole data across the NAIP. Lava flows are chosen for focus as they represent the most favorable reservoir target identified to date whilst also often constituting the dominant facies within much of the accessible NAIP offshore sequences.Over 50 offshore boreholes have penetrated the lava sequences of the NAIP including both industry and scientific boreholes drilled from the 1970’s onwards. Boreholes have encountered anything from a single lava flow through to several 10’s of lava flows in volcanic sequences reaching over 2 km in cumulative thickness in the deepest industry wells such as Brugdan (6104/21-1) and Lagavulin (217/15-1z) in the Faroese and UK sectors respectively.A summary of the lava flow nature (simple, compound, thickness, core-crust ratios) and physical property ranges (P-wave velocity, density, resistivity) of the penetrated lava flow sequences is presented utilizing available core, sidewall core, wireline and drill cuttings data to support the facies appraisal.Borehole data and the level of possible interpretation vary significantly depending on the age, purpose, and importantly the drilling operations of the individual boreholes. Some of the most robust and complete datasets are represented by modern hydrocarbon industry boreholes, for example those from the Rosebank Field in the UK sector, and cored boreholes from recent IODP Expedition 396 drilling Mid-Norway. Results from Expedition 396 are presented to highlight formation evaluation approaches for NAIP lava flow sequences including assessing the effects of different lava flow facies on Net to Gross calculations and the impact of alteration and secondary alteration on wireline log responses.This study presents important new constraints on the nature, variability, and distribution of NAIP lava flows from extensive available borehole ground truth data forming a foundational study for the development of reservoir appraisal techniques in the province going forward.

• Tugend, Julie; Mohn, Geoffroy; Kusznir, Nick, J.; Planke, Sverre; Berndt, Christian & Zastrozhnov, Dmitrii [Show all 7 contributors for this article] (2025). Paleo-depth of hydrothermal venting along the Mid-Norwegian volcanic margin during Paleogene continental breakup. doi: 10.5194/egusphere-egu25-10746. Full text in Research Archive Show summary

  Volcanic rifted margins commonly form in association with the emplacement of Large Igneous Provinces. The intense associated volcanic activity coincides with shifts in the global carbon cycle and rapid climate change during several key geological periods and crises. The Mid-Norwegian and NE-Greenland conjugate rifted margins formed after late Paleocene to early Eocene continental breakup in association with the emplacement of the North Atlantic Igneous Province (NAIP). The NAIP and early opening of the North Atlantic occurred contemporaneous to a rapid 5-6 °C global warming episode known as the Paleocene Eocene Thermal Maximum (PETM). The rapid global warming documented during the PETM is hypothesized to result from the release of thermogenic gases into the atmosphere through thousands of hydrothermal vents. The gases were generated by contact metamorphism of carbon-rich sediments during the extensive sill emplacement from the NAIP. The potential climatic impact of these hydrothermally released greenhouse gases is dependent on the water depth at which they were released. Unless it is released in a shallow marine environment most methane, known for its significantly greater global warming potential compared to carbon dioxide, will be oxidized and dissolved in the ocean before it reaches the atmosphere.First results of IODP Expedition 396 conducted on the Mid-Norwegian volcanic margin have documented the shallow marine to potentially sub-aerial setting of at least one of the hydrothermal vents (i.e. Modgunn vent). However, a comprehensive regional assessment of the water depth at which hydrothermal venting occurred remains necessary to validate the overall impact on paleoclimate and the PETM. To do so, we apply 3D flexural-backstripping and decompaction to remove the loading effects of sedimentary sequences and determine the sediment-corrected bathymetry down to the top Palaeocene surface at which most of the vents are mapped. Reverse subsidence cannot be directly modelled without knowing the detailed distribution of syn- and post-rift thermal subsidence from Cretaceous and Paleocene rifting as well as any mantle plume dynamic uplift during NAIP emplacement. Because these tectonic and geodynamic components of subsidence cannot be deterministically predicted at the required accuracy, we use local palaeobathymetric constraints from seismic observations and drilled biostratigraphic data, combined with our flexural backstripping and decompaction results to calibrate palaeobathymetric variations of the Paleocene venting surface at the time of the PETM.Our results predict that hydrothermal venting occurred within a range of palaeo-water depths showing the complex palaeo-structure of the top Paleocene surface. Key post-Paleocene tectonic influences such as a well-documented Miocene doming episode influence the margin history, and hence, at this location, our palaeobathymetric results represent shallowest estimates and must be interpreted with caution. However, most of the vents (>80%) restore to bathymetries shallower than 500 meters, i.e., in sub-aerial to shallow marine conditions. Our work aims to confirm and extend initial results of IODP Expedition 396 from the Modgunn vent. Shallow water-depth hydrothermal venting most likely occurred during magma-rich continental breakup and NAIP emplacement; a large part of the released hydrogenic gas could have directly contributed to the global warming recorded by the PETM. 

• Galerne, Christophe; Sinha, Aniruddha; Bach, Wolfgang; Kahl, Wolf-Achim; Millett, John & Planke, Sverre (2025). Pore-fluid pressure assisted columnar joint initiation: a natural carbon trapping process revealed from IODP Expedition 396 basalt samples. doi: 10.5194/egusphere-egu25-20273. Full text in Research Archive Show summary

  Extensive flood basalt sequences of the North Atlantic Igneous Province (NAIP) offshore Norway comprise promising sequestration reservoirs for permanent CO2 on the doorstep of Europe. However, a key question remains open: How much of the pore space is available at present for Carbon Capture and Sequestration (CCS) endeavours?We investigated carbonate vein and void mineral fills in drill core samples from IODP Expedition 396 which recovered over 350 m of basaltic stratigraphy, to untangle the formation conditions of the carbonates and the origin of the carbon. We examined two main scenarios: carbonates originating from 1) dissolved carbon in seawater, or from 2) thermogenic gas ascending from greater depths within the basin. Several driving mechanisms for this second scenario are explored: natural migration of light petroleum derived from burial and/or contact metamorphism associated with later sill emplacement at depth.We present results of carbon and oxygen isotope analyses of carbonate found distributed down section of the landward-flow volcanic sequence (Site U1566) and the outer seaward-dipping reflector (SDR) sequence of flows (Site U1573). Oxygen isotope thermometry suggests a range of formation temperatures between 50 and 160°C. However, results from micro-CT textural analyses and petro-chemical analyses suggests that some carbonate originated from thermogenic gas at much higher temperature. We interpret these signatures as relating to the early nucleation of contractional cooling joints (columnar joint fractures) in the basaltic lava at the time of emplacement. Newly obtained carbon and oxygen isotopes from this type of carbonate will be presented and discussed.Our result suggests an alternative third scenario in which carbonate originating from below the flood basalts seals the porosity and reduces permeability in the lower section of the SDR sequence. Textural analysis indicates that thermogenic gases mobilized during lava flow emplacement assist in initiating and sealing columnar joint fractures. If confirmed, this process implies that the SDR lava flow sequence above the first lava flow may be relatively carbonate-free, as it is sealed off from post-emplacement thermogenic gas fluxes ascending from depth.

• Planke, Sverre; Berndt, Christian; Huismans, Ritske Sipke; Faleide, Jan Inge; Bünz, Stefan & Millett, John [Show all 8 contributors for this article] (2025). Understanding Volcanic Rifted Margins and Paleoclimate Implications from Scientific Drilling in the NE Atlantic. doi: https:/ui.adsabs.harvard.edu/abs/2024AGUFMPP44A..02P/abstract. Full text in Research Archive
• Lebedeva-Ivanova, Nina N.; Bünz, Stefan; Berndt, Christian; Millett, John; Betlem, Peter & Zastrozhnov, Dmitry [Show all 9 contributors for this article] (2025). High-resolution 2D and 3D seismic imaging and core-log-seismic integration of seaward dipping reflectors on the Vøring volcanic rifted margin. doi: 10.5194/egusphere-egu25-12935. Full text in Research Archive Show summary

  Offshore basalt flow sequences represent potential permanent CO2 sequestration sites along volcanic rifted margins. The International Ocean Discovery Program (IODP) Expedition 396 drilled six basement sites on the Vøring volcanic margin in 2021, recovering more than 350 m of basaltic basement cores and 15 m of granite cores. The cores have been extensively analyzed following the IODP shipboard procedures (e.g., velocity, density, porosity, and magnetic susceptibility measurements). In addition, shore-based petrographic, geochemical, CT scanning, and multi-fluid permeability and flow measurements (nitrogen, brine, liquid and gaseous CO2) have been performed to assess reservoir properties. A standard suite of conventional wireline logs along with borehole image (acoustic and resistivity) logs were acquired in four holes. High-resolution 2D and locally 3D seismic reflection data have been acquired across all sites during three surveys (2020, 2022, and 2024) using R/V Helmer Hansen. In total, four HR3D P-Cable cubes with a total areal extent of 62 km2 and c. 2700 km of HR2D data have been collected. The seismic data are interpreted using the concepts of seismic volcanostratigraphy and igneous seismic geomorphology combined with conventional horizon interpretation and core-log-seismic integration. On the Skoll High, the igneous seismic geomorphology of the Top Basalt horizon reveals two distinct domains: a pitted surface in the west, and a faulted surface in the east. Cross-cutting faults and fracture systems are well imaged in borehole data and the 3D seismic data. Borehole data show that the Inner Seaward Dipping Reflectors (SDR) were emplaced in subaerial and coastal environments, including vesicular flow tops and deposition of inter-basalt volcaniclastic sedimentary horizons. Vesicles are observed to be both open or filled with carbonates and clay minerals within different layers, however, laboratory measured matrix permeability of mini-core plugs is typically low and in the milli to micro-darcy range; brine permeability measurements are indicating even lower. Multiple scales of fracturing are identified within the cores and image logs, and Strontium residual salt analysis revealed that they have an important impact on permeability by enhancing fluid communication between flows. In conclusion, the integrated interpretation suggests that the Vøring Margin basalt sequences may have reservoir potential in fractured intervals and flow tops, but reservoir-scale injection testing linked to fracture network parameterization is required for large-scale assessment.

• Planke, Sverre; Bünz, Stefan; Berndt, Christian; Zarikian, Carlos A. Alvarez; Lebedeva-Ivanova, Nina N. & Stokke, Henrik Henriksen [Show all 18 contributors for this article] (2025). The Ocean-Continent Transition of the Northern Vøring Margin from New High-Resolution 2D Seismic and IODP Expedition 396 Data. Full text in Research Archive
• Bünz, Stefan; Planke, Sverre; Berndt, Christian; Lebedeva-Ivanova, Nina N.; Stokke, Henrik Henriksen & Binde, Cornelia Mentzoni [Show all 14 contributors for this article] (2025). High-resolution 3D seismic imaging of Northeast Atlantic volcanic break‐up processes. doi: https:/www.geologi.no/konferanser/vinterkonferanser/abstracts/file/298-abst-vk25. Full text in Research Archive Show summary

  During the NE Atlantic breakup in the Paleogene, extensive magmatic activity resulted in the formation of approximately 6–10 Mkm3 of extrusive basaltic deposits and intrusion of magma into sedimentary basins. This magmatism, along with the degassing and explosive release of thermo‐ genic gases due to contact metamorphism, has been linked to the onset of the Paleocene‐Eocene Thermal Maximum (PETM; 56 Ma). During IODP Expedition 396, 21 boreholes were drilled at 10 sites across five geological settings on the mid‐ Norwegian Margin. These sites sampled diverse igneous and sedimentary environments, including lava flow fields, hydrothermal vent complexes (HTVCs), and thick Paleogene strata. In addition, UiT The Arctic University of Norway conducted three research expeditions in 2020, 2022 and 2024 to acquire high‐resolution 2D/3D seismic and multibeam data in order to tie IODP borehole sites together and to regional geology. This presentation focusses on the two high‐resolution 3D seismic surveys, one of which that was repeated during the 2024 expedition to study repeatability effects in basalts. A high‐resolution P‐Cable 3D seismic cube (10 by 2.4 km, 6.25x6.25 m bin size) was collected over the Modgunn Arch (Sites U1567 and U1568), where we have identified a shallowly buried HTVC, known as the Modgunn Vent, and associated sill intrusions. Contact metamorphism of sedimentary rocks generates volatile compounds, generating an overpressure that leads to fracturing of the overlying sediments. As the hot fluids and gases escape through the fractures, they reach the sea‐ floor and create HTVCs. These complexes consist of a large crater structure that is subsequently filled in by sediments some of which may result from erupted material. The vent fill may be alter‐ ed by fluid migration and/or tectonic stress leading to folding and doming. Another high‐resolution 3D seismic survey (10.3 x 1.8 km, 6.25x6.25 m bin size) was conducted on the Skoll High at the northern Vøring margin (Sites U1571 and U1572). The 3D seismic data images the top basalt showing the volcanic paleo‐land‐ scape in unprecedented details. A faulted and eroded lava horizon is observed in the southeast‐ ern cube at 150–250 m depth. In contrast, the northwestern cube shows a pitted surface with lobate structures and linear ridges. These features are interpreted as rootless cones, volcanic craters formed by explosive interactions between lava flows and water‐saturated sediments. This study showcases the exceptional level of detail achievable through high‐resolution 3D seis‐ mic data acquisition of hydrothermal vent complexes and buried volcanic landscapes, offering new opportunities for unique insights in the Northeast Atlantic break‐up processes and beyond

• Polteau, Stephane; Smalley, Craig; Millett, John; Planke, Sverre; Rosenqvist, Marija Plahter & Devegowda, Vani [Show all 7 contributors for this article] (2025). Vertical fluid connectivity of basalt sequence assessed using strontium isotopes in pore waters. Full text in Research Archive
• Polteau, Stephane; Craig, Smalley,; Millett, John; Planke, Sverre; Rosenqvist, Marija Plahter & V., Devegowda, [Show all 7 contributors for this article] (2025). The fluid connectivity of continental margin basalt sequences for CO2 storage revealed by strontium isotopes. Full text in Research Archive
• Planke, Sverre; Millett, John; Lebedeva-Ivanova, Nina N.; Bünz, Stefan; Jones, Morgan Thomas & Myklebust, R. (2024). Cretaceous and Paleogene Source Rock Potential on the Norwegian Atlantic Margin. doi: 10.3997/2214-4609.2024101502. Full text in Research Archive

View all works in NVA