Center Of Plume Research Articles

Devonian–Mississippian magmatism related to extensional collapse in Svalbard: implications for radiating dyke swarms

Background Despite extensive studies of the Mesozoic–Cenozoic magmatic history of Svalbard, little has been done on the Paleozoic magmatism due to fewer available outcrops. Methods 2D seismic reflection data were used to study magmatic intrusions in the subsurface of eastern Svalbard. Results This work presents seismic evidence for west-dipping, Middle Devonian–Mississippian sills in eastern Spitsbergen, Svalbard. The sills crosscut a late Neoproterozoic Timanian thrust system, which was reworked during Caledonian contraction. The sills are unconformably overlain by relatively undeformed Pennsylvanian–Mesozoic sedimentary rocks and crosscut by Cretaceous dykes of the High Arctic Large Igneous Province. The sills probably intruded along extensional fractures during post-Caledonian reactivation–overprinting of the late Neoproterozoic thrust system. Kimberlitic accessory minerals in exposed contemporaneous intrusions and the chemical composition of chromium spinel grains in Upper Triassic sedimentary rocks in Svalbard suggest that the Middle Devonian–Mississippian intrusions in eastern Spitsbergen show affinities with diamond-rich kimberlites in northwestern Russia. Overall, the sills were emplaced during a regional episode of extension-related Devonian–Carboniferous magmatism in the Northern Hemisphere including the Kola–Dnieper and Yakutsk–Vilyui large igneous provinces. Conclusions This work presents the first evidence for extensive Middle Devonian–Mississippian magmatism in Svalbard. These intrusions may be part of the Kola–Dnieper Large Igneous Province and intruded parallel to preexisting, Proterozoic–early Paleozoic orogenic structures. Their strike is inconsistent with a source from a potential mantle plume center in the eastern Barents Sea. Thus, the radiating emplacement pattern of the magmatic intrusions of the Kola–Dnieper Large Igneous Province are not the product of plume-related uplift but of structural inheritance. A similar line of reasoning is successfully applied to intrusions of the Yakutsk–Vilyui and High Arctic large igneous provinces.

Enhancing Uncrewed Aerial Vehicle Techniques for Monitoring Greenhouse Gas Plumes at Point Sources

The urgency of the global climate crisis necessitates advanced monitoring of greenhouse gases, with an emphasis on capturing their spatial and temporal variability. This study explores techniques to enhance plume detection and concentration measurements using uncrewed aerial vehicles (UAVs) for monitoring at point sources, specifically at an incineration stack. Through preliminary site investigations, our approach employed strategically designed flight paths and an autopilot system to optimize flight operations within the constraints of limited flight time due to battery capacity. We combined a UAV-mounted anemometer with a plume rise model to localize the plume center at a distance of 30 m from the stack center and evaluated its performance by comparing the model-based estimations at different altitudes and angular directions with the observation results. The comparison demonstrated that the results obtained by localizing the plume center using a plume rise model and a UAV-mounted anemometer aligned well with observations based on CO2 concentration analysis. The comparative analysis showed a RMSE of 8.44 m and a MAE of 7.26 m for altitude, and a RMSE of 32.31∘ and a MAE of 25.78∘ for angular direction. Furthermore, we assessed the effectiveness of hovering UAV flights, in which a UAV remains stationary at a fixed point in the air, compared to non-hovering flights in capturing pollutant concentration. While both methods performed similarly in detecting the plume center, non-hovering flights underestimated the CO2 concentration due to insufficient time for measurement despite a sensor response time of less than three seconds. Overall, our proposed hybrid monitoring strategy integrates non-hovering and hovering flights, enhancing both plume detection efficiency and concentration measurement accuracy at point sources.

Laser-induced breakdown spectroscopy for helium detection in beryllium coatings

Laser Induced Breakdown Spectroscopy (LIBS) method is considered to be a promising tool for analyzing the retention of hydrogen isotopes (D and T) and helium (He) on the first walls and divertor regions of future fusion reactors. Helium will be produced in DT reactions but could also be used in the initial non-nuclear phases of DEMO concepts. The present study investigates the He detection by LIBS method in the Be coatings simulating the deposits on the divertor plasma-facing components of JET while the results are also relevant for He detection in the deposits of other wall materials. The study was carried out in a vacuum vessel filled with 2–40 mbar argon background gas. It was shown that 2.8 at. % of He was confidently detectable by LIBS at optimized measurement conditions and the estimated limit of detection at used experimental conditions is approximately 0.7 at. %. The intensity of the He emission line at 587.56 nm was the strongest at the center of the laser-induced plasma plume. The He line intensity increased with the pressure of Ar gas but the broadening of the He line and the increase of the background emission and noise set an upper limit to the Ar background pressure usable for He detection. The application of the calibration-free LIBS procedure resulted in the overestimation of the He/Be ratio by several orders of magnitude. The overestimation can be explained by the deviation of LIBS plasma from the local thermodynamic equilibrium, which is caused by the very high excitation energy of He atoms.

Shortwave infrared polarization characteristics simulation of solid rocket plume with self-emission and external incident radiation

Polarization optical detection has been widely used in the detection and identification of particle containing media such as clouds, aerosols, fire plumes, and volcanic smoke. Solid rocket plume is a typical high-temperature gas–solid two-phase medium. Polarization optical detection of solid rocket plume has attracted much attention in recent years. The polarized radiation transfer mechanism of solid rocket plume is complex, especially in the infrared band, with both the scattering radiation transfer from external incident light and the scattering radiation transfer from the high-temperature region inside the jet flame to the outside. The research on the polarization scattering characteristics of solid jet flame still needs to be further developed. Therefore, this study focuses on modeling the infrared polarization scattering mechanism and the simulation of polarization transfer characteristics of a solid rocket gas–solid two-phase plume, which can guide the usability analysis of solid rocket plume polarization detection. A novel model based on Semi-analytic Monte Carlo Method is proposed to simulate polarized radiation transfer of solid rocket plume. The wavelength and angle dependence of the self-radiation polarization characteristic of a solid rocket plume is simulated based on the proposed model. Note that the overall polarization degree of the plume shows wavelength selectivity and angle sensitivity at different wavelengths. The spatial distribution of polarization degree at 1.55 μm, 2.2 μm, and 2.75 μm shows that the plume edge's polarization degree is higher than the plume center. The findings suggest that the ratios of the relative contribution of self-radiation, direct solar radiation, and background polarization radiation components to the total polarization characteristics are 0.47 %, 70.50 %, 29.03 % at 1.55 μm and 20.43 %, 79.55 %, 0.02 % at 2.75 μm.

Experimental study for visualizing CO2-dissolved water plume migration under hydraulic gradient conditions and implication for field monitoring data

Investigating the possible direction of a CO2-dissolved water plume migration near the potential CO2 leakage area is a significant task because it helps estimate the spatial and temporal monitoring scale to detect the signal of released CO2 from the storage. Accordingly, the Korea CO2 Storage Environmental Management (K-COSEM) research center tried to develop an intensive monitoring system and applied it to the artificial CO2 release test in the actual field. Monitoring data from the field tests depicted the horizontal movement of the CO2-dissolved water plume along the direction of the groundwater flow. However, it remains unclear how the CO2-dissolved water plume migrates vertically and how gas accumulation occurs near the capillary zone. The present study simulated the CO2 release test with a visual expression method utilizing a Hele-Shaw cell with hydraulic gradient conditions (i = 0, 0.1, and 0.01) and tried to estimate the significant influences on a diffusive-advective transport of the dissolved gas plume with the shallow aquifer condition. The visualization experiment results were intuitively verified to determine whether the theoretical principles of action related to plume flow applied in this context. The results suggest that a CO2-dissolved water plume is distributed by hydraulic gradients and density-driven CO2 convective flow. The plume shape, center, and area were analyzed using an image analyzer program; the results demonstrated that the plume characteristic evolved depending on the significant effects on the plume. When the plume was mainly affected by the hydraulic gradient, it rapidly moved from the injection point to the last boundary; in contrast, when it was influenced primarily by density-driven CO2 convective flow, it flowed diagonally downward in the shape of varied branches. The numerical model calculated the migration of the CO2-dissolved water plume affected by both factors. The laboratory experiment and numerical simulation results suggest that the migration of a CO2-dissolved water plume may be affected by the hydraulic gradient and density-driven CO2 convective transport. As such, these factors should be considered when designing and analyzing CO2 monitoring signals to detect CO2 leaks from shallow aquifer systems.

Geological history of the Atira Mons large shield volcano, Beta Regio, Venus.

Atira Mons is a large (∼300,000 km2) low-relief (1.8 km) shield volcano, with individual flows extending up to ∼700 km from the central caldera. It is located about 3000 km NW from the major plume center Beta Regio. Detailed mapping of the flows (at 1:500,000 scale, 10x more detailed than previous mapping) has identified fifty-three flow units which are grouped into eleven packages. Flow units are distinguished based on radar brightness, topography, morphology, continuity, structural modification, and sources, while flow packages group flows with clear stratigraphic relationship affinity.Cross-cutting relationships indicate a complex and multi-episodic eruption history with provisional identification of six mapped stages. The most voluminous flows are concentrated in the early stages, while the younger pulses, with a few exceptions, are shorter and less voluminous. A central caldera hosts the youngest volcanism with flows breaching its eastern side. Multiple stages of caldera collapse are indicated.The volume of the volcano is estimated using various methods and yields values range from ∼47,000 to ∼270,000 km3. The larger estimates are consistent with that of the magma volume of Large Igneous Provinces (LIP) on Earth. An appropriate terrestrial analogue is the Benham Rise Oceanic LIP in the western margin of the Philippine Sea, and particularly the Apolaki Caldera, which is the world's largest known basaltic caldera with a diameter of ∼150 km.

Mass spectrometric analysis of unprecedented high levels of carbonaceous aerosol particles long-range transported from wildfires in the Siberian Arctic

Abstract. Wildfires in Siberia generate large amounts of aerosols, which may be transported over long distances and pose a threat to the sensitive ecosystem of the Arctic. Particulate matter (PM) of aged wildfire plumes originating from Yakutia in August 2021 was collected in Nadym and on Bely Island (both in northwestern Siberia). An advanced analysis of the chemical composition of aerosol particles was conducted through a multi-wavelength thermal–optical carbon analyzer (TOCA) coupled to resonance-enhanced multiphoton ionization time-of-flight mass spectrometry (REMPI-TOFMS) as well as through ultra-high-resolution Fourier-transform ion cyclotron resonance mass spectrometry (FT-ICR MS). In Nadym, concentrations of organic carbon (OC) and elemental carbon (EC) peaked at 100 and 40 µg m−3, respectively, associated with Angström absorption exponents for 405 and 808 nm (AAE405/808) between 1.5 and 3.3. The weekly average on Bely Island peaked at 8.9 µg m−3 of OC and 0.3 µg m−3 of EC and AAE405/808 close to unity. In particular, ambient aerosol in Nadym had a distinct biomass burning profile with pyrolysis products from carbohydrates, such as cellulose and hemicellulose, as well as lignin and resinoic acids. However, temporarily higher concentrations of five- and six-ring polycyclic aromatic hydrocarbons (PAHs), different from the PAH signature of biomass burning, suggest a contribution of regional gas flaring. FT-ICR MS with electrospray ionization (ESI) revealed a complex mixture of highly functionalized compounds, containing up to 20 oxygen atoms, as well as nitrogen- and sulfur-containing moieties. Concentrations of biomass burning markers on Bely Island were substantially lower than in Nadym, flanked by the appearance of unique compounds with higher oxygen content, higher molecular weight, and lower aromaticity. Back-trajectory analysis and satellite-derived aerosol optical depth suggested long-range transport of aerosol from the center of a Yakutian wildfire plume to Nadym and from the plume periphery to Bely Island. Owing to lower aerosol concentrations in the plume periphery than in its center, it is demonstrated how dilution affects the chemical plume composition during atmospheric aging.

2,4,6-TCP migrates and transforms in different cultivated soil in China: Kinetic analysis and mechanistic modeling

Organochlorine pesticides are widely used in agriculture, wood preservation, pulp bleaching and other fields, which increased the pollution risk of cultivated land. In this study, a typical organochlorine pesticides-2,4,6-TCP was conducted as the target pollutants to investigated the migration and transformation characteristics in different cultivated soils in China. The results indicated that the adsorption of 2,4,6-TCP in soil samples was in order: black soil＞laterite＞fluvo-aquic soil, and the maximum adsorption was 71.0870, 27.0575 and 6.1292 mg/kg, respectively. The dispersion coefficient of black soil, laterite and fluvo-aquic soil was 0.0329, 0.0501 and 0.0149, and the hysteretic factor R was 5.381, 1.455 and 2.238, respectively, indicating that the migration ability of 2,4,6-TCP in different cultivated soils samples was in order: black soil＞laterite＞fluvo-aquic soil. The fitting results of one-dimensional migration model indicated that the model well reflected the migration and transformation of 2,4,6-TCP in different cultivated soil samples. Meanwhile, the Two-dimensional migration model fitting results indicated that the maximum concentration of 2,4,6-TCP of different cultivated soil samples were found along the longitudinal flow direction, reaching 40% of the initial pollution concentration at 15 m, corresponding to the center of the pollutant plume.

KENGEDE MAFIC DYKE SWARM AND EXPANSION OF THE 1.50 Ga KUONAMKA LARGE IGNEOUS PROVINCE OF NORTHERN SIBERIA

Within the Anabar shield in the northern part of the Siberia, Late Precambrian mafic igneous units are widespread, which form dyke swarms of different ages of different trends. This paper presents new data on the composition, structure and U-Pb dating of the E-W trending Kengede dyke swarm. Three new U-Pb ID-TIMS baddeleyite ages (1496±7, 1494±3 and 1494±5 Ma) were obtained from three dykes, indicating that the Kengede swarm is part of the 1500 Ma Kuonamka large igneous province (LIP). The previously recognized Kuonamka Large Igneous Province (LIP) extends for 700 km from the Anabar shield to the Olenek uplift in the northern part of the Siberia and is potentially linked to coeval dykes and sills of the São Francisco craton and the Congo craton. The newly dated Kengede swarm is parallel to but offset by 50 km from the previously dated 1501±3 Ma Kuonamka swarm, and the identification of these two subparallel dyke subswarms of the Kuonamka LIP supports the earlier interpretation that mantle plume centre was located along the extrapolated trend of the dykes near the eastern or western margin of the Siberia. The paper examines features of sulfide Cu-Ni mineralization in dolerites of the Kengede and East Anabar dyke swarms and discusses potential Cu-Ni-sulfide mineralization linked to the Precambrian mafic dyke swarms of different ages in the north-east of the Siberia.

Dyke swarms record the plume stage evolution of the Atla Regio superplume on Venus

Atla Regio, Venus, is interpreted as a young major mantle plume centre, and we address whether it is at plume head or plume tail stage. Our approach uses graben-fissure lineaments, interpreted as the surface expression of dykes. Mapping > 40,000 such lineaments reveals giant radiating dyke swarms associated with major volcanic centres of Maat (>1500 km dyke swarm radius), Ozza (>2000 km), Ongwuti (>1100 km) and Unnamed montes (>1100 km), indicating that each is due to plume head magmatism rather than plume tail magmatism (maximum swarm length ~ 100 km). The size of an underlying flattened plume head is estimated by the radius where the swarm transitions from a radiating to linear pattern. All four centres and their plume heads group within the 1200 km radius of the Ozza Mons plume head, consistent with a single event. Atla Regio is at the plume head stage with coeval triple-junction rifting, which on Earth would typically precede attempted continental breakup.

Identification of the ca. 720 Ma Irkutsk LIP and its plume centre in southern Siberia: The initiation of Laurentia-Siberia separation

Widespread 720 Ma magmatism has been linked with the break-up of Rodinia and the onset of the Sturtian ‘Snowball Earth’ event. We report a new U-Pb baddeleyite age from the Baikal dyke subswarm in southern Siberia which increases the known extent of the 720 Ma Irkutsk LIP and confirms a previous hypothesis that the Baikal and Sayan subswarms converge at the southern tip of the Irkutsk promontory. Together they define a mantle plume centre with direct links to the 720 Ma Franklin plume centre of northern Laurentia, thus constraining the paleo-reconstruction of southern Siberia and northern Laurentia. It is inferred that this combined 720 Franklin – Irktusk LIP event is associated with the breakup of southern Siberia from northern Laurentia during fragmentation of the Rodinia supercontinent. Expansion of 720 Ma magmatism into Siberia greatly increases the scale of the Franklin-Irktusk LIP.

Spectral turbulence kinetic energy budget and scale-based velocity decomposition for turbulence in bubble plumes

We conducted a spectral analysis of the turbulence kinetic energy (TKE) budget in a bubble plume using particle image velocimetry with fluorescent particles. Our findings confirmed the hypothesis of an inverse energy cascade in the bubble plume, where TKE is transferred from small to large eddies. This is attributed to direct injection of TKE by bubble passages across a wide range of scales, in contrast to canonical shear production of TKE in large scales. Turbulence dissipation was identified as the primary sink of the bubble-produced TKE and occurred at all scales. The decomposition of velocities using the critical length scale of inter-scale energy transfer allowed us to distinguish between large- and small-scale motions in the bubble plume. The large-scale turbulent fluctuations exhibited a skewed distribution and were likely associated with the return flow after bubble passage and the velocities induced by the bubble wake. The small-scale turbulent fluctuations followed a Gaussian distribution relatively well. The large-scale motions contributed to over half of the Reynolds stresses, while there were significant small-scale contributions to the normal stresses near the plume center but not to the shear stress. The large-scale motions in the vorticity field induced a street of vertically elongated vortex pairs, while the small-scale vortices exhibited similar sizes in both horizontal and vertical directions.

A newly developed Lagrangian chemical transport scheme: Part 1. Simulation of a boreal forest fire plume

Forest fire research over the last several decades has improved the understanding of fire emissions and impacts. Nevertheless, the evolution of forest fire plumes remains poorly quantified and understood. Here, a Lagrangian chemical transport model, the Forward Atmospheric Stochastic Transport model coupled with the Master Chemical Mechanism (FAST-MCM), has been developed to simulate the transport and chemical transformations of plumes from a boreal forest fire over several hours since their emission. The model results for NOx (NO and NO2), O3, HONO, HNO3, pNO3 and 70 VOC species are compared with airborne in-situ measurements within plume centers and their surrounding portions during the transport. Comparisons between simulation results and measurements show that the FAST-MCM model can properly reproduce the physical and chemical evolution of forest fire plumes. The results indicate that the model can be an important tool used to aid the understanding of the downwind impacts of forest fire plumes.

Variations in Volcanism and Tectonics Along the Hotspot‐Influenced Reykjanes Ridge

AbstractMapping and sampling four sections of the slow‐spreading Reykjanes Ridge provide insight into how tectonic and volcanic activity varies with distance from the Iceland plume. The studied areas are characterized by significant variations in water depth, lava chemistry, crustal thickness, thermal structure, and ridge morphology. For each study area, fault pattern and dimension, tectonic strain, seamount morphology, and density are inferred from 15 m‐resolution bathymetry. These observations are combined with geochemical analysis from glass samples and sediment thickness estimations along Remotely Operated Vehicle‐dive videos. They reveal that (a) tectonic and volcanic activity along the Reykjanes Ridge, do not systematically vary with distance from the plume center. (b) The tectonic geometry appears directly related to the deepening of the brittle/ductile transition and the maximum change in tectonic strain related to the rapid change in crustal thickness and the transition between axial‐high and axial valley (∼59.5°N). (c) Across‐axis variations in the fault density and sediment thickness provide similar widths for the neo‐volcanic zone except in regions of increased seamount emplacement. (d) The variations in seamount density (especially strong for flat‐topped seamounts) are not related to the distance from the plume but appear to be correlated with the interaction between the V‐shape ridges (VSR) flanking the ridge and the ridge axis. These observations are more compatible with the buoyant upwelling melting instability hypothesis for VSR formation and suggest that buoyant melting instabilities create many small magma batches which by‐pass the normal subaxial magmatic plumbing system, erupting over a wider‐than‐normal area.

Linear Stochastic Analysis of the Partial Reversibility of Ensemble and Effective Dispersion in Heterogeneous Porous Media

AbstractMacrodispersion in heterogeneous formations is caused by spatial variability of the velocity field, making different parts of a plume experience different advective displacements. Differential advection interacts with diffusion, which hardly affects longitudinal ensemble dispersion (i.e., the spread of the ensemble‐averaged concentration) but determines effective dispersion, that is, the expected spread of individual plumes for point injections. The latter has been suggested as metric of solute mixing. Pure advection is fully reversible, whereas diffusion is completely irreversible. We quantify the partial reversibility of macrodispersion by analyzing the second central ensemble and effective spatial moments for advective‐diffusive transport in heterogeneous domains with flow reversal, applying linear stochastic theory to approximate the corresponding moments and comparing them to particle‐tracking random‐walk simulations in periodic media. Diffusion causes solute particles to deviate from their forward trajectories when flow is reversed. As long as advective memory dominates, both types of second central moments decrease during backward motion, then reach a minimum, and increase again. The reversibility is considerably bigger for ensemble than effective dispersion but the latter also shows partial reversibility, challenging its use as metric of mixing. The stronger diffusion is in comparison to advection, the less reversible dispersion becomes. After equally long times of forward and backward motion, the two types of second central moments differ, but to a much smaller extent than in pure forward motion. In realistic settings, the advective memory affects dispersion so strongly that the asymptotic regime is not reached before the plume center has returned to its origin.

Geochemistry and petrogenesis of Late Permian basalts from the Sichuan Basin, SW China: Implications for the geodynamics of the Emeishan mantle plume

Plume-lithosphere interactions are significant in the formation of Large Igneous Provinces (LIPs). The Permian Emeishan Large Igneous Province (ELIP) is considered to be the result of a mantle plume. The Emeishan flood basalts comprise a major part of the ELIP and they define three zones: the inner, intermediate and outer zones. Both high-Ti and low-Ti basalts are present in the inner zone, whereas only high-Ti basalts are found in the intermediate zone and outer zone. However, there are only sparse outcrops in the outer zone, and so geochemical data on basalts from the outer zone are rare and the role of plume-lithosphere interaction in the petrogenesis of volcanic rocks in the outer zone remains poorly understood. In the Sichuan basin, the Basalt Formation is found between the Permian Maokou Formation limestone and the Longtan Formation marl in some drill cores as well as in outcrops in the basin. This relationship demonstrates that the basaltic layer in the basin is part of the Emeishan flood basalts. These basalts have TiO2 contents of 3.7–4.2 wt% and Ti/Y ratios of 604–720, being high-Ti sub-alkaline basalts. They display chondrite-normalized rare earth elements (REE) patterns enriched in light rare earth elements (LREE) relative to heavy rare earth elements (HREE) and have elevated large ion lithophile elements (LILE) and high field strength elements (HFSE). Lead isotope ratios are high (206Pb/204Pb(t) = 18.102–18.392, 207Pb/204Pb(t) = 15.578–15.606, 208Pb/204Pb(t) = 38.410–38.850), and εNd(t) values are −0.38 ∼ 1.17. Detailed petrology and geochemistry suggest that the high-Ti basalts from the Sichuan Basin did not experience significant contamination of crustal and lithospheric mantle material during the ascent of magma. We infer that these basalts resulted from low-degree melting of the plume mantle source and underwent fractional crystallization of clinopyroxene. The distribution and petrogenesis of the Sichuan Basin basalts in the outer zone are different from those of the basalts in the inner zone and there are clearly different plume-lithosphere interactions in different parts of the ELIP. In the inner zone, the temperature of the lithosphere mantle was markedly elevated due to underplating of the mantle plume, causing a substantial quantity of lithosphere mantle melting and the initial formation of low-Ti basalts. This was followed by melting of the mantle plume and the formation of high-Ti basalts. In the outer zone, lower temperatures further from the plume centre were insufficient to generate extensive melting of the lithospheric mantle. Consequently, only the mantle plume melted in the outer zone, resulting in the formation of high-Ti basalts with minimal lithospheric input.

Plume-induced flood basalts on Hesperian Mars: An investigation of Hesperia Planum

Hesperian Mars was characterized by a unique style of geodynamic activity that left crucial volcano-tectonic records in the form of extensive flood lavas covered by wrinkle ridges. Yet, little is known about the context of their formation. Here, we perform a tectonic and geophysical investigation of Hesperia Planum, a 1700-km-diameter volcanic plain covered by wrinkle ridges. Our tectonic analysis reveals that the planum has the highest density of wrinkle ridges on the planet and a characteristic compressional peak strain of about 3.20 × 10−3, almost 2 times larger than typical Hesperian compressional strains. We invert gravity and topography data and find that simple crustal loading and volcanism cannot explain the tectonic record. An additional source of deformation is thus required. We demonstrate that a loading sequence of plume-induced uplift, volcanism, and subsidence, following an evolutionary path similar to flood basalt provinces on Earth better fits the observations. This plume model is able to explain the peak strain, crustal thinning, and low relief of Hesperia Planum. The inferred plume head size (∼1400 km) and temperature anomaly (∼320 K) are consistent with large terrestrial plumes. Based on a fit to the tectonic record, we determine a plume center location that correlates with a cluster of wrinkle ridges, local crustal thinning, and a circular magnetic low, where the latter could be the result of a thermal demagnetization of the lithosphere in the presence of the ascending plume. Our analysis suggests that scattered mantle plumes could be at the origin of Hesperia Planum and other late Noachian to early Hesperian volcanic provinces within the highlands.

Exploring rift geodynamics in Ethiopia through olivine-spinel Al-exchange thermometry and rare-earth element distributions

Understanding the process of continental break-up requires knowledge of the geodynamics of mature rift systems close to the point of plate rupture. In Ethiopia, late-stage continental rifting occurs in a magma-rich setting where extensional processes correlate closely with magmatic and volcanic activity. Unravelling the role that mantle and lithospheric dynamics play in sustaining rifting in Ethiopia is key to improving models of late-stage continental rift evolution. In this study we provide petrological constraints on the physical characteristics of magma production using volcanic samples from the northern Main Ethiopian Rift (MER) and central Afar. Olivine crystallisation temperatures provide information about the thermal state of mantle-derived magmas generated by the mantle during upwelling and melting. These temperatures, determined by Al-exchange thermometry, are used in conjunction with other geochemical and geophysical constraints in inversion models of melting a multi-lithology mantle to find the best-fitting geodynamic parameters that can reproduce observed magma compositions and melt volumes. Our model results suggest that the potential temperature of the Ethiopian mantle is hotter than ambient mantle by ≥ 150∘C, and is elevated to a similar degree across the MER and Afar. We predict significant variations in lithospheric thickness between the MER (90 km) and Afar (50-70 km), with Afar also likely to have a higher portion of fusible mantle domains. This thinner lithosphere and/or more productive mantle is required to generate the larger volumes of magma inferred to have been intruded into the Afar crust. The geodynamic differences between these two settings can be attributed to the more-evolved state of the Afar rift and its proximity to the centre of the Afar plume.

Recycled Crustal Components of the Iceland Plume Centre: Ultra-Dehydrated Crust and Oxidised Water-Bearing Fertile Mantle

AbstractPrimitive basalts erupted mainly above the proposed centre of the Iceland plume have been analysed geochemically. The data shed light on the distribution of plume heterogeneities and constrain their nature and origin. Low-Ca (down to 1420 ppm) olivine macrocrysts and chromite inclusions in Snæfell rocks of the eastern flank zone indicate that the magmas were hydrous (c. 2 wt% H2O) and relatively oxidised (fO2 = c. ΔQMF+1). Al-in-olivine crystallisation temperatures indicate that magmas from central Iceland magmas are not hotter than from other parts of Iceland. Some Gæsafjöll rocks with high Nb/U = 110–120 from the northern rift zone (NRZ) represent magmas widespread in Iceland that are also characterised by low Ba/La and high La/U, La/Th, Nb/Th and Ce/Pb. They reflect a mantle component with Nb/U ≈ 200 present in many basalts of all rift zones. This mantle apparently consists of peridotite refertilised by ultra-dehydrated recycled oceanic crust (ROC). This component is in clear contrast to the main source of the Snæfell magmas, which is modelled to be peridotite strongly refertilised by enriched ROC more hydrous than Mid-Ocean Ridge Basalt. In contrast to more-depleted rift zone melts, which are extracted from depths just below the thin rifted lithosphere, some rift zone basalts are extracted deeper and produced by intermediate degrees of melting of the two types of refertilised mantle. Snæfell-type melts are common in the NRZ and eastern rift zones (ERZ) and most strongly present at Upptyppingar. Mixing of magmas is indicated at crustal levels. Mantle melting may be modelled for homogeneous sources of peridotite or olivine websterite. Double-spike Pb isotope analyses suggest that the depleted mantle sources of the ERZ basalts together with Snæfell and high-Nb/U sources, both with 206Pb/204Pb = 18.3–18.6, Δ207Pb ≈ 0 and Δ208Pb = 20–30, explain both ERZ and NRZ magmas, except for Theistareykir. They are distinct from magmas of the western rift zone, which is characterised by melt contributions from a differently enriched mantle with more radiogenic lead, negative Δ207Pb, Δ208Pb ≈ 0. This difference in type of enriched mantle suggests that the Iceland mantle plume is laterally zoned.

Numerical Study of the Bubble Behavior of a Ladle with Different Purging Plug Designs

The purging plug determines the downtime and usage efficiency of the ladle‐refining process. Therefore, the optimization of its geometry can improve the ladle performance. Herein, suitable boundary conditions for numerical simulations are derived by combining water model experiments with numerical simulations. Furthermore, the influence of various parameters, such as the distribution shape of the circular slits and spacing between the circles on the bubble size, is investigated. The results show that rectangular distribution facilitates the reduction of bubble size compared to circular distribution because of the larger slit spacing to bubble diameter () of the rectangular distribution. In addition, distributing more circular slits around the edge of the purging plug reduces the pressure gradient generated by the velocity difference from the center of the bubble plume to the sides and increases , which can decrease the probability of coalescence. Therefore, it is beneficial to reduce the overall bubble size in the ladle when the circular slits are more distributed at the edge of the purging plug.