Deep electrical imaging of the ultraslow-spreading Mohns Ridge

Johansen, Ståle Emil; Panzner, Martin; Mittet, Rune; Amundsen, H. E. F.; Lim, Anna; Vik, Eirik; Landrø, Martin; Arntsen, Børge

doi:10.1038/s41586-019-1010-0

Cited by 71 publications

(58 citation statements)

References 38 publications

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“…Topography is rough and has a pronounced difference between the ridge flanks, reflecting the complexity of the spreading history of the Norwegian‐Greenland basins. The asymmetry is expressed at multiple levels and is attributed to the oblique and asymmetric motion of the European and North American plates rather than asymmetric sediment loading, which barely follows the basement topography (Johansen et al, ; Talwani & Eldholm, ; P Vogt et al, ). Both flanks of the rift valley and the valley floor are covered by sediments from the Bear Island Fan with thickness reaching up to ~800 m with larger volumes deposited on the eastern side (Bruvoll et al, ).…”

Section: Geological Settingmentioning

confidence: 99%

“…The life cycle of an AVR alternates between magmatic and tectonic phases, following the intermittent magmatic and tectonic focusing and defocusing along the axis due to restricted magma supply (Parson et al, ). The area is seismically active—earthquake epicenters located within the ridge valley closely correlates with the major faults and volcanoes at the graben floor, suggesting a tight link between melt placement and faulting processes (Hopper et al, ; International Seismological Centre, ; Johansen et al, ). The interplay between these processes is of major importance for hydrothermal circulation along the ridges (McCaig et al, ).…”

Section: Geological Settingmentioning

confidence: 99%

“…The Mohns ultra‐slow‐spreading ridge hosts five vent sites (Figure a), two of these sites are discussed in this paper. Loki's Castle is an active basalt‐hosted vent field investigated by several research cruises (Baumberger et al, ; Johansen et al, ; Ludvigsen et al, ; Pedersen, Thorseth , et al, ). High‐resolution magnetic data, however, are presented in this paper for the first time.…”

Section: Introductionmentioning

confidence: 99%

“…Regional, publicly available bathymetry (Norwegian Mapping Authority, ), electromagnetic and magnetotelluric data (Johansen et al, ), reflection seismic data (Bruvoll et al, ) proved to be highly instrumental in understanding and describing large‐scale processes driving hydrothermal circulation. However, the localization of the associated deposits within the permissive tracts, favorable for exploration, is still not well understood and mainly based on probabilistic assessment rather than on geological and physical characteristics (Juliani & Ellefmo, ).…”

Section: Introductionmentioning

confidence: 99%

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Hydrothermal Activity at the Ultraslow‐Spreading Mohns Ridge: New Insights From Near‐Seafloor Magnetics

Lim

Brönner

Johansen

et al. 2019

Geochem Geophys Geosyst

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Hydrothermal circulation is a process fundamental to all types of mid-ocean ridges that largely impacts the chemical and physical balance of the World Ocean. However, diversity of geological settings hosting hydrothermal fields complicates the exploration and requires thorough investigation of each individual case study before effective criteria can be established. Analysis of high-resolution bathymetric and magnetic data, coupled with video and rock samples material, furthers our knowledge about mid-ocean-ridge-hosted venting sites and aid in the interpretation of the interplay between magmatic and tectonic processes along the axial volcanic ridges. The rock-magnetic data provide constraints on the interpretation of the observed contrasts in crustal magnetization. We map the areal extent of the previously discovered active basalt-hosted Loki's Castle and inactive sediment-hosted Mohn's Treasure massive sulfide deposits and infer their subsurface extent. Remarkably, extinct hydrothermal sites have enhanced magnetizations and display clear magnetic signatures allowing their confident identification and delineation. Identified magnetic signatures exert two new fossil hydrothermal deposits, MT-2 and MT-3. The Loki's Castle site coincides with negative magnetic anomaly observed in the 2-D magnetic profile data crossing the deposit. First geophysical investigations in this area reveal the complexity of the geological setting and the variation of the physical properties in the subsurface.

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Section: Geological Settingmentioning

confidence: 99%

Section: Geological Settingmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Hydrothermal Activity at the Ultraslow‐Spreading Mohns Ridge: New Insights From Near‐Seafloor Magnetics

Lim

Brönner

Johansen

et al. 2019

Geochem Geophys Geosyst

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“…These data sets contain complementary information about the model (their compatible regions do not overlap completely), so the region of parameter space compatible with the joint data set should be smaller than either of them (the shaded, overlapping region). (Mitrovica & Forte 2004); and, most recently, marine MT and CSEM data collected at a slow spreading mid-ocean ridge (Johansen et al 2019). Most joint inversion studies can be classified according to whether all data sets inform the same underlying model parameters (e.g.…”

Section: Introductionmentioning

confidence: 99%

Bayesian joint inversion of controlled source electromagnetic and magnetotelluric data to image freshwater aquifer offshore New Jersey

Blatter

Key

Ray

et al. 2019

Geophysical Journal International

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SUMMARY Joint inversion of multiple electromagnetic data sets, such as controlled source electromagnetic and magnetotelluric data, has the potential to significantly reduce uncertainty in the inverted electrical resistivity when the two data sets contain complementary information about the subsurface. However, evaluating quantitatively the model uncertainty reduction is made difficult by the fact that conventional inversion methods—using gradients and model regularization—typically produce just one model, with no associated estimate of model parameter uncertainty. Bayesian inverse methods can provide quantitative estimates of inverted model parameter uncertainty by generating an ensemble of models, sampled proportional to data fit. The resulting posterior distribution represents a combination of a priori assumptions about the model parameters and information contained in field data. Bayesian inversion is therefore able to quantify the impact of jointly inverting multiple data sets by using the statistical information contained in the posterior distribution. We illustrate, for synthetic data generated from a simple 1-D model, the shape of parameter space compatible with controlled source electromagnetic and magnetotelluric data, separately and jointly. We also demonstrate that when data sets contain complementary information about the model, the region of parameter space compatible with the joint data set is less than or equal to the intersection of the regions compatible with the individual data sets. We adapt a trans-dimensional Markov chain Monte Carlo algorithm for jointly inverting multiple electromagnetic data sets for 1-D earth models and apply it to surface-towed controlled source electromagnetic and magnetotelluric data collected offshore New Jersey, USA, to evaluate the extent of a low salinity aquifer within the continental shelf. Our inversion results identify a region of high resistivity of varying depth and thickness in the upper 500 m of the continental shelf, corroborating results from a previous study that used regularized, gradient-based inversion methods. We evaluate the joint model parameter uncertainty in comparison to the uncertainty obtained from the individual data sets and demonstrate quantitatively that joint inversion offers reduced uncertainty. In addition, we show how the Bayesian model ensemble can subsequently be used to derive uncertainty estimates of pore water salinity within the low salinity aquifer.

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One-Sided Joint Inversion of Shear Velocity and Resistivity from the PI-LAB Experiment at the Equatorial Mid-Atlantic Ridge

Harmon¹,

Wang²,

Rychert³

et al. 2021

Preprint

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Deep electrical imaging of the ultraslow-spreading Mohns Ridge

Cited by 71 publications

References 38 publications

Hydrothermal Activity at the Ultraslow‐Spreading Mohns Ridge: New Insights From Near‐Seafloor Magnetics

Hydrothermal Activity at the Ultraslow‐Spreading Mohns Ridge: New Insights From Near‐Seafloor Magnetics

Bayesian joint inversion of controlled source electromagnetic and magnetotelluric data to image freshwater aquifer offshore New Jersey

One-Sided Joint Inversion of Shear Velocity and Resistivity from the PI-LAB Experiment at the Equatorial Mid-Atlantic Ridge

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