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The formation and preservation of compositional heterogeneities inside the Earth affect mantle convection patterns globally and control the long-term evolution of geochemical reservoirs. However, the distribution, nature, and size of reservoirs in the Earth’s mantle are poorly constrained. Here, we invert measurements of travel times and amplitudes of seismic waves interacting with mineralogical phase transitions at 400–700-km depth to obtain global probabilistic maps of temperature and bulk composition. We find large basalt-rich pools (up to 60% basalt fraction) surrounding the Pacific Ocean, which we relate to the segregation of oceanic crust from slabs that have been subducted since the Mesozoic. Segregation of oceanic crust from initially cold and stiff slabs may be facilitated by the presence of a weak hydrated layer in the slab or by weakening upon mineralogical transition due to grain-size reduction.

We estimate the mantle source compositions for mantle plumes and, by implication, Earth's lower mantle by: (1) measuring trace (e.g, Sc, V, Cu) and minor (e.g., Ca, Mn, Ni) element concentrations of high-forsterite olivine grains from several plume localities, (2) estimating the parent liquid compositions from which they crystallized, (3) calculating mantle potential temperatures and degrees of partial melting, and (4) estimating trace element compositions of depleted and enriched mantle sources. Our sample set includes two continental flood basalt provinces (Emeishan and Deccan), a flood basalt that erupted in a continental rift setting (Baffin Island), our type example of a thermal mantle plume (Hawaii), and lavas from the Siqueiros Transform at the East Pacific Rise, which represent the mid-ocean ridge system. We also present olivine (Ol) compositions for peridotite xenoliths from Kilbourne Hole, New Mexico, U.S.A., which are commonly used as primary and secondary analytical standards. We find that trace elements in lava-hosted olivine grains are too far removed from their mantle source to provide anything but greatly hindered views of such. Olivine compositions reflect not only evolving liquid compositions (including partial melting conditions and later fractionation), but also evolving Ol+liq partition coefficients, which mostly increase with decreasing T during crystallization. Mantle compositions, delimited by maximum forsterite contents and estimates of parental magmas (and experimentally determined partition coefficients) indicate that our selected plumes reflect some combination of (1) a depleted mantle source that is quite similar to that obtained by other methods and (2) a variably enriched plume source that is more enriched than current estimates of pyrolite. The enriched plume mantle sources can be explained remarkably well as a mixture of subducted mid-ocean ridge basalt (MORB; Gale et al. 2013) and depleted MORB mantle (DM; Salters and Stracke 2004), with MORB:DMM ratios of 1:5 to 1:4. These ratios are most sensitive to estimates of melt fraction where plume parental magmas are last equilibrated with their mantle source, but are nonetheless consistent across a wide range of chemically very different elements, and estimates of MORB and DM obtained by very different means. Baffin Island is of particular interest. Like prior studies, we verify a high mantle potential temperature (Tp) of 1630 °C (compared to Tp = 1320-1420 °C for MORB from Cottrell and Kelley 2011 for Ol of Fo89.3-91.4). The Baffin source is also within error the same as DM with respect to trace elements, although still isotopically distinct; Baffin appears to be sourced in something that is akin to DMM that lies at the base of the mantle, where plumes acquire their excess heat. Thus while part of our analysis supports the concept of a \"slab graveyard\" at the bottom of the lower mantle (e.g., Wyession 1996), that cemetery is by no means ubiquitous at the CMB: subducted slabs are either unevenly interred, or efficiently excavated by later upwellings.

The North Atlantic region is a complex geodynamic setting that comprises multiple continental blocks, sedimentary basins, mid‐ocean ridge systems and prominent hotspots. Recent geophysical surveys of the near‐surface have enhanced our understanding of crustal elements and the shallow lithosphere. However, our knowledge of the deep lithospheric structure and the physical state and dynamics of the upper mantle is still limited. Here, we exploit the combined sensitivity of surface‐wave data, geoid anomalies, absolute topography and surface heat flow to obtain full thermochemical models of the region from the surface down to 350 km. We jointly invert these data sets using a simulation‐based, multi‐observable probabilistic framework. We validate our results with independent thermobarometric and chemical information from mantle xenoliths and test the effects of using different seismic models on the inversion results. Our model reveals an intricate sublithospheric flow system, driven by the interaction of deep upwellings with the highly irregular lithospheric structure. We corroborate that the main thermal anomaly in the sublithospheric mantle shows a tilted geometry, moving toward Greenland with depth. We reveal that this large‐scale anomaly transition into a more complex pattern once it reaches depths of ∼${\\sim} $ 150 km beneath the North Atlantic. Small‐scale downwellings originate from the margins of continental domains, resulting in a complex circulation pattern that limits the radial spread of the deep upwellings and preferentially focuses them within regions of thin lithosphere along a N–S direction. Distinct compositional anomalies in the Greenland lithosphere delineate the North Atlantic Craton, the Nagssugtoqidian mobile belt, and the covered remnants of the Disko Craton. In continental Europe, the East European Craton shows clear indications of depletion in incompatible elements, with the Kola‐Karelian cratonic region showing the highest levels of depletion. Our model serves as a base to make interpretations on the enigmatic paleotectonic history of the North‐Atlantic region. Plain Language Summary The North Atlantic region and its surrounding continental areas are geologically fascinating, encompassing significant tectonic features that are important for both scientific research and societal benefits. While recent studies have illuminated surface and shallow layers, much remains unknown about the deeper structure and dynamics‐critical for constraining ice‐sheet models, post‐glacial rebound, and guiding mineral exploration. To explore these hidden depths, we combined data from seismic surface waves, gravitational anomalies, topography, and heat flow. This integration allowed us to create detailed models extending down to 350 km beneath the Earth's surface. Our research revealed a complex and dynamic flow system beneath the North Atlantic, where deep upwellings interact with the irregular lithosphere, creating intricate circulation patterns. This interaction triggers smaller downwellings at the continental edges and deflects upwellings along thinner lithosphere, primarily along a north–south axis. We also identified unique compositional features in Greenland's lithosphere, such as the North Atlantic Craton and Nagssugtoqidian mobile belt. These findings enhance our understanding of the Earth's interior in this region and provide valuable insights into future exploration of critical minerals, geothermal energy, and the region's ancient tectonic history. Key Points A data‐driven model of the thermochemical and dynamic state of the lithosphere‐asthenosphere system beneath the North Atlantic region and surroundings Complex sublithospheric flow driven by the interaction of deep upwellings with a highly irregular lithospheric structure Compositional anomalies delineate known and unknown boundaries between tectonic blocks and are supported by independent xenolith data

Halogens are important tracers of various planetary formation and evolution processes, and an accurate understanding of their abundances in the Earth’s silicate reservoirs can help us reconstruct the history of interactions among mantle, atmosphere, and oceans. The previous studies of halogen abundances in the bulk silicate Earth (BSE) are based on the assumption of constant ratios of element abundances, which is shown to result in a gross underestimation of the BSE halogen budget. Here we present a more robust approach using a log-log linear model. Using this method, we provide an internally consistent estimate of halogen abundances in the depleted mid-ocean ridge basalts (MORB)-source mantle, the enriched ocean island basalts (OIB)-source mantle, the depleted mantle, and BSE. Unlike previous studies, our results suggest that halogens in BSE are not more depleted compared to elements with similar volatility, thereby indicating sufficient halogen retention during planetary accretion. According to halogen abundances in the depleted mantle and BSE, we estimate that ∼87% of all stable halogens reside in the present-day mantle. Given our understanding of the history of mantle degassing and the evolution of crustal recycling, the revised halogen budget suggests that deep halogen cycle is characterized by efficient degassing in the early Earth and subsequent net regassing in the rest of Earth history. Such an evolution of deep halogen cycle presents a major step toward a more comprehensive understanding of ancient ocean alkalinity, which affects carbon partitioning within the hydrosphere, the stability of crustal and authigenic minerals, and the development of early life.

The geochemical study of the Earth＇s mantle provides important constraints on our understanding of the formation and evolution of Earth, its internal structure, and the mantle dynamics. The bulk Earth composition is inferred by comparing terrestrial mantle rocks with chondrites, which leads to the chondritic Earth model. That is, Earth has the same relative proportions of refractory elements as that in chondrites, but it is depleted in volatiles. Ocean island basalts （OIB） may be produced by mantle plumes with possible deep origins; consequently, they provide unique opportunity to study the deep Earth. Isotopic variations within OIB can be described using a limited number of mantle endmembers, such as EM1, EM2 and HIMU, and they have been used to decipher important mantle processes. Introduction of crustal material into the deep mantle via subduction and delamination is important in generating mantle heterogeneity; however, there is active debate on how they were sampled by mantle melting, i.e., the role of olivine-poor lithologies in the OIB petrogenesis. The origin and location of high 3He/4He mantle remain controversial, ranging from unprocessed （or less processed） primitive material in the lower mantle to highly processed materials with shallow origins, including ancient melting residues, mafic cumulates under arcs, and recycled hydrous minerals. Possible core-mantle interaction was hypothesized to introduce distinctive geochemical signatures such as radiogenic 186Os and Fe and Ni enrichment in the OIB. Small but important variations in some short-lived nuclides, including 142Nd, 182W and several Xe isotopes, have been reported in ancient and modern terrestrial rocks, implying that the Earth＇s mantle must have been differentiated within the first 100 Myr of its formation, and the mantle is not efficiently homogenized by mantle convection.

The elasticity of minerals at high temperature and pressure （PT） is critical for constraining the composition and temperature of the Earth＇s interior and understand better the deep water cycle and the dynamic Earth. First-principles calcula- tions without introducing any adjustable parameters, whose results can be comparable to experimental data, play a more and more important role in investigating the elasticity of minerals at high PT mainly because of （1） the quick increasing of computational powers and （2） advances in method. For example, the new method reduces the computation loads to one-tenth of the traditional method with the comparable precise as the traditional method. This is extraordinarily helpful because first-principles calculations of the elasticity of minerals at high PT are extremely time-consuming. So far the elasticity of most of lower mantle minerals has been investigated in detail. We have good idea on the effect of temperature, pressure, and iron concentration on elasticity of main minerals of the lower mantle and the unusual softening in bulk modulus by the spin crosso- ver of iron in ferropericlase. With these elastic data the lower mantle has been constrained to have 10-15 wt% ferropericlase, which is sufficient to generate some visible effects of spin crossover in seismic tomography. For example, the spin crossover causes that the temperature sensitivity of P wave at the depth of -1700 km is only a fraction of that at the depth of -2300 kin. The disruptions of global P wave structure and of P wave image below hotspots such as Hawaii and Iceland at similar depth are in consistence with the spin crossover effect of iron in ferropericlase. The spin crossover, which causes anomalous ther- modynamic properties of ferropericlase, has also been found to play a control role for the two features of the large low shear velocity provinces （LLSVPs）： the sharp edge and high elevation up to 1000 km above core-mantle boundary. All these results clearly suggest the spin crossover of iron in the lower mantle. The theoretical investigations for the elasticity of minerals at the upper mantle and water effect on elasticity of minerals at the mantle transition zone and subducting slab have also been con- ducted extensively. These researches are critical for understanding better the composition of the upper mantle and water dis- tribution and transport in the Earth＇s mantle. Most of these were static calculations, which did not include the vibrational （temperature） effect on elasticity, although temperature effect on elasticity is basic because of high temperature at the Earth＇s interior and huge temperature difference between the ambient mantle and the subducting slab. Including temperature effect on elasticity of minerals should be important future work. New method developed is helpful for these directions. The elasticity of iron and iron-alloy with various light elements has also been calculated extensively. However, more work is necessary in order to meet the demand for constraining the types and amount of light elements at the Earth＇s core. Keywords Mantle temperature, Mantle composition, Composition of Earth＇s core, Ab initio method

Recent advances in computational petrological modeling provide accurate methods for computing seismic velocities and density within the lithospheric and sub‐lithospheric mantle, given the bulk composition, temperature, and pressure within them. Here, we test an integrated geophysical‐petrological inversion of Rayleigh‐ and Love‐wave phase‐velocity curves for fine‐scale lithospheric structure. The main parameters of the grid‐search inversion are the lithospheric and crustal thicknesses, mantle composition, and bulk density and seismic velocities within the crust. Conductive lithospheric geotherms are computed using P‐T‐dependent thermal conductivity. Radial anisotropy and seismic attenuation have a substantial effect on the results and are modeled explicitly. Surface topography provides information on the integrated density of the crust, poorly constrained by surface waves alone. Investigating parameter inter‐dependencies, we show that accurate surface‐wave data and topography can constrain robust lithospheric models. We apply the inversion to central Mongolia, south of the Baikal Rift Zone, a key area of deformation in Asia with debated lithosphere‐asthenosphere structure and rifting mechanism, and detect an 80–90 km thick lithosphere with a dense, mafic lower crust and a relatively fertile mantle composition (Mg# < 90.2). Published measurements on crustal and mantle Miocene and Pleistocene xenoliths are consistent with both the geotherms and the crustal and lithospheric mantle composition derived from our inversion. Topography can be fully accounted for by local isostasy, with no dynamic support required. The mantle structure constrained by the inversion indicates no major thermal anomalies in the shallow sub‐lithospheric mantle, consistent with passive rifting in the Baikal Rift Zone. Key Points Petro‐physical inversion reduces non‐uniqueness of seismic surface‐wave inversion No evidence for thermal anomaly in the uppermost mantle in central Mongolia Topography is consistent with local isostasy with no dynamic component required

This review paper focuses on joint modelling and interpretation of electromagnetic data and other geophysical and petrological observables. In particular, integrated geophysical–petrological modelling approaches, where the electrical conductivity and other physical properties of rocks are required to be linked by the common subsurface thermochemical conditions within a self-consistent thermodynamic framework, are reviewed. The paper gives an overview of the main geophysical electromagnetic techniques/data sets employed in lithospheric and mantle imaging including recent advances using satellite data, and an up-to-date summary of the most relevant laboratory experiments regarding the electrical conductivity of upper mantle minerals for various temperature–pressure–water conditions. The sensitivity of electrical conductivity and other geophysical parameters (density, seismic velocities) of mantle rocks to changes in temperature and composition are presented based on a Monte Carlo method parameter exploration. Finally, a case study in Central Tibet is presented where both seismological (long-period surface wave phase velocities) and electromagnetic (magnetotelluric) data—simultaneously including the constraints offered by topography, surface heat flow and mantle xenoliths—have been integrated. The modelling is based on a self-consistent petrological-geophysical thermodynamic framework where mantle properties are calculated as a function of temperature, pressure, and composition. The Tibetan case study offers an excellent opportunity to illustrate the different and complementary sensitivities of the various data sets used and to show how integrated thermochemical models of the lithosphere can help understand settings with a complex tectonic evolution.

We jointly invert local fundamental‐mode and higher‐order surface‐wave phase‐velocities for radial models of the thermo‐chemical and anisotropic physical structure of the Earth's mantle to ∼1000 km depth beneath the North American continent. Inversion for thermo‐chemical state relies on a self‐consistent thermodynamic method whereby phase equilibria and physical properties (P‐, S‐wave velocity and density) are computed as functions of composition (in the Na2O‐CaO‐FeO‐MgO‐Al2O3‐SiO2 model system), pressure and temperature. We employ a sampling‐based strategy to solve the non‐linear inverse problem relying on a Markov Chain Monte Carlo method to sample the posterior distribution in the model space. A range of models fitting the observations within uncertainties are obtained from which any statistics can be estimated. To further refine sampled models we compute geoid anomalies for a collection of these and compare with observations, exemplifying a posteriori filtering through the use of additional data. Our thermo‐chemical maps reveal the tectonically stable older eastern parts of North America to be chemically depleted (high Mg#) and colder (>200°C) relative to the active younger regions (western margin and oceans). In the transition zone the thermo‐chemical structure decouples from that of the upper mantle, with a relatively hot thermal anomaly appearing beneath the cratonic area that likely extends into the lower mantle. In the lower mantle no consistent large‐scale thermo‐chemical heterogeneities are observed, although our results do suggest distinct upper and lower mantle compositions. Concerning anisotropy structure, we find evidence for a number of distinct anisotropic layers pervading the mantle, including transition zone and upper‐most lower mantle. Key Points Stochastic inversion of surface‐wave phase velocities Thermo‐chemical structure beneath North America Posterior filtering of tomography models using geoid anomalies

The pyrolite model is one of the possible compositions of the Earth's lower mantle. The lower mantle's composition is generally modelled by comparing seismic observations with mineral physics data of possible lower mantle end‐member phases. Here, we report the compression behavior of a natural KLB‐1 peridotite (a representative composition of the pyrolite model) in a quasi‐hydrostatic environment at simultaneous high pressure (P) and temperature (T), covering the entire range of lower mantle P‐T conditions up to 112 GPa. This is the first experimentally determined density profile of pyrolite under the lower mantle conditions. The results allow us to directly compare the measured density of peridotite mantle along the geotherm with the Preliminary Reference Earth Model (PREM) derived from seismic observations, without extrapolation. The comparison shows significant mismatch between the two, which calls for a re‐evaluation of the PREM density model or a non‐pyrolite lower mantle composition.