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The lithium supply issue mainly lies in the inability of current mining methods to access lithium sources of dilute concentrations and complex chemistry. Electrochemical intercalation has emerged as a highly selective method for lithium extraction; however, limited source compositions have been studied, which is insufficient to predict its applicability to the wide range of unconventional water sources (UWS). This work addresses the feasibility and identifies the challenges of Li extraction by electrochemical intercalation from UWS, by answering three questions: 1) Is there enough Li in UWS? 2) How would the solution compositions affect the competition of Li⁺ to major ions (Na⁺/Mg2+/K⁺/Ca2+)? 3) Does the complex solution composition affect the electrode stability? Using one-dimensional olivine FePO₄ as the model electrode, we show the complicated roles of major ions. Na⁺ acts as the competitor ion for host storage sites. The competition from Na⁺ grants Mg2+ and Ca2+ being only the spectator ions. However, Mg2+ and Ca2+ can significantly affect the charge transfer of Li⁺ and Na⁺, therefore affecting the Li selectivity. We point to improving the selectivity of Li⁺ to Na⁺ as the key challenge for broadening the minable UWS using the olivine host.

Earth’s water cycle enables the incorporation of water (hydration) in mantle minerals that can influence the physical properties of the mantle. Lattice thermal conductivity of mantle minerals is critical for controlling the temperature profile and dynamics of the mantle and subducting slabs. However, the effect of hydration on lattice thermal conductivity remains poorly understood and has often been assumed to be negligible. Here we have precisely measured the lattice thermal conductivity of hydrous San Carlos olivine (Mg0.9Fe0.1)₂SiO₄ (Fo90) up to 15 gigapascals using an ultrafast optical pump–probe technique. The thermal conductivity of hydrous Fo90 with ∼7,000 wt ppm water is significantly suppressed at pressures above ∼5 gigapascals, and is approximately 2 times smaller than the nominally anhydrous Fo90 at mantle transition zone pressures, demonstrating the critical influence of hydration on the lattice thermal conductivity of olivine in this region. Modeling the thermal structure of a subducting slab with our results shows that the hydration-reduced thermal conductivity in hydrated oceanic crust further decreases the temperature at the cold, dry center of the subducting slab. Therefore, the olivine–wadsleyite transformation rate in the slab with hydrated oceanic crust is much slower than that with dry oceanic crust after the slab sinks into the transition zone, extending the metastable olivine to a greater depth. The hydration-reduced thermal conductivity could enable hydrous minerals to survive in deeper mantle and enhance water transportation to the transition zone.

Mare volcanics on the Moon are the key record of thermo-chemical evolution throughout most of lunar history 1 – 3 . Young mare basalts—mainly distributed in a region rich in potassium, rare-earth elements and phosphorus (KREEP) in Oceanus Procellarum, called the Procellarum KREEP Terrane (PKT) 4 —were thought to be formed from KREEP-rich sources at depth 5 – 7 . However, this hypothesis has not been tested with young basalts from the PKT. Here we present a petrological and geochemical study of the basalt clasts from the PKT returned by the Chang’e-5 mission 8 . These two-billion-year-old basalts are the youngest lunar samples reported so far 9 . Bulk rock compositions have moderate titanium and high iron contents  with KREEP-like rare-earth-element and high thorium concentrations. However, strontium–neodymium isotopes indicate that these basalts were derived from a non-KREEP mantle source. To produce the high abundances of rare-earth elements and thorium, low-degree partial melting and extensive fractional crystallization are required. Our results indicate that the KREEP association may not be a prerequisite for young mare volcanism. Absolving the need to invoke heat-producing elements in their source implies a more sustained cooling history of the lunar interior to generate the Moon’s youngest melts. Isotopic analysis of basalt clasts returned from the Moon by the Chang’e-5 mission indicates that the rocks were derived from a mantle source that lacked potassium, rare-earth elements and phosphorus.

The mantle near Earth's subduction zones endures intense deformation that generates anisotropic rock textures. These textures can be observed seismically and modeled geodynamically, but the complexity of this deformation makes analyses of these textures difficult. In this study, we apply time‐series clustering analysis to tracers within subduction models, allowing for the identification of regions in the subduction zone with common deformation histories and olivine crystallographic‐preferred orientation development. We compare olivine texture evolution predicted using different methods in both retreating and stationary‐trench settings. Our results reveal distinct variations in olivine texture, indicating that both seismic and viscous anisotropy can exhibit substantial heterogeneity within the mantle wedge, sub‐slab, and subducting plate regions. For retreating trenches, olivine textures are strongest in the mid‐depth mantle wedge region about 200 km away from the trench between 100 and 300 km depth. Our study shows that trench‐normal olivine a‐axis orientations dominate in the center of subduction zones. Toroidal flow around slab edges generates a mix of trench‐normal, trench‐parallel, and oblique fast seismic directions. Textures and anisotropy are stronger for the retreating trench model than for the stationary trench model since more deformation has been accumulated due to trench motion. These findings provide insights for interpreting seismic anisotropy in subduction zones and highlight the importance of considering texture heterogeneity, as characterized by clustering algorithms, when analyzing both geodynamic models and seismic observations of subduction zones.

We performed triaxial compressive creep experiments on aggregates of San Carlos olivine to develop a flow law and to examine microstructural development in the dislocation‐accommodated grain boundary sliding regime (GBS). Each experiment included load and temperature steps to determine both the stress exponent and the activation energy. Grain boundary maps, created with electron backscatter diffraction data, were used to quantify grain size distributions for each sample. Inversion of the resulting data produced the following flow law for GBS: GBS = 104.8 ± 0.8 (σ2.9 ± 0.3/d0.7 ± 0.1) exp[(−445 ± 20 kJ mol−1)/RT], with σ, d, and GBS in units of MPa, μm, and s−1, respectively. Although relatively weak, crystallographic‐preferred orientations (CPOs) have [010] maxima parallel to the compression direction along with [100] and [001] girdles perpendicular to the compression direction. CPOs and subgrain boundary misorientation axes suggest that the (010)[100] slip system contributes significantly to deformation. We propose that these experimental results are best modeled by a deformation mechanism in which strain is accomplished primarily through grain boundary sliding accommodated by the motion of dislocations. Extrapolation of our flow laws to mantle conditions suggests that GBS is likely to be the dominant deformation mechanism in both lithospheric shear zones and asthenospheric flow, and therefore strong upper mantle seismic anisotropy can not be attributed solely to the dominance of dislocation creep. Key Points We determined a flow law for the grain boundary sliding (GBS) regime Extrapolations of our flow law imply that GBS is dominant in the upper mantle Observed crystallographic fabrics agree with patterns of seismic anisotropy

The kinetics of the reaction (Mg,Fe)‐olivine + H2O → serpentine + magnetite + brucite + H2 were investigated at 500 bars in the 250–350°C range using natural olivine (San Carlos; Fo91) with grain sizes between 1 and 150 μm and for run durations up to 514 d. The amount of magnetite produced, which directly relates to reaction progress, was accurately monitored using up to 24 time‐resolved magnetic measurements per experiment. Eighty percent of serpentinization was achieved after 60 d for olivine grain sizes of 5–15μm and after 500 d for grain sizes of 50–63 μm. Serpentinization kinetics were found to be inversely proportional to the geometrical surface area of the starting olivine grains. They were one or two orders of magnitude slower than serpentinization kinetics commonly used for modeling serpentinization‐related processes. The nature of the serpentine mineral product depended on the initial olivine grain size (IGS); for IGS in the 5–150μm range lizardite formed, and olivine dissolution was the rate‐limiting process. At IGS below 5μm, chrysotile crystallized instead of lizardite, and the relationship between olivine surface area and reaction kinetics no longer held. We infer that for such small olivine grain sizes dissolution is no longer the rate‐limiting process. Serpentinization in our experiments was associated with the creation of new reactive surface area according to two cooperative processes: etch pits formation associated with dissolution and grain fracturing for IGS above 20μm. Interestingly, fractures and etch pits with similar geometry and sizes were also observed for residual olivine (with a typical grain size of 50 μm) in serpentinized peridotite samples from the Southwest Indian Ridge. This suggests that the processes governing olivine serpentinization kinetics in our experiments are similar to those prevailing in natural systems. We therefore suggest that the new kinetic data set that we present here, which encompasses a range of olivine grain sizes and reaction temperatures, is relevant to the serpentinization of olivine in the oceanic crust insofar as water is available. Key Points Experimental study of the kinetics of olivine serpentinization Influence of temperature and olivine initial grain size (IGS) on the kinetics Reactive surface area increases with etch pits and fractures

The mechanical properties of olivine-rich rocks are key to determining the mechanical coupling between Earth’s lithosphere and asthenosphere. In crystalline materials, the motion of crystal defects is fundamental to plastic flow 1 – 4 . However, because the main constituent of olivine-rich rocks does not have enough slip systems, additional deformation mechanisms are needed to satisfy strain conditions. Experimental studies have suggested a non-Newtonian, grain-size-sensitive mechanism in olivine involving grain-boundary sliding 5 , 6 . However, very few microstructural investigations have been conducted on grain-boundary sliding, and there is no consensus on whether a single or multiple physical mechanisms are at play. Most importantly, there are no theoretical frameworks for incorporating the mechanics of grain boundaries in polycrystalline plasticity models. Here we identify a mechanism for deformation at grain boundaries in olivine-rich rocks. We show that, in forsterite, amorphization takes place at grain boundaries under stress and that the onset of ductility of olivine-rich rocks is due to the activation of grain-boundary mobility in these amorphous layers. This mechanism could trigger plastic processes in the deep Earth, where high-stress conditions are encountered (for example, at the brittle–plastic transition). Our proposed mechanism is especially relevant at the lithosphere–asthenosphere boundary, where olivine reaches the glass transition temperature, triggering a decrease in its viscosity and thus promoting grain-boundary sliding. Amorphization at grain boundaries in olivine-rich rocks under stress and consequent grain-boundary sliding could explain the decrease in viscosity between the lithosphere and the asthenosphere.

Olivine (Fo80-88) from the Shitoukengde deposit exhibits low levels of Ca, Cr, and Al (< 220 ppm) and varying Ni content. The low Ca-Cr-Al contents in olivine and subsolidus temperatures (600–900 °C) indicated by olivine-spinel thermometers align with subsolidus equilibria, emphasizing substantial postcumulus modifications. Therefore, the postcumulus effect must be considered when applying olivine-spinel oxybarometers to intrusive rocks. Back-calculating the spinel Fe–Mg contents to magmatic temperature, the estimated oxidation fugacity (fO2) range between FQM − 1.5 and FQM − 3.0, approximately 0.5 to 1.5 ΔFQM more reduced compared to those calculated from the raw spinel composition. Moreover, the fO2 aligns with results obtained from the olivine-sulfide pair (FMQ − 3.0 to FMQ 0). The considerably reducing state and wide oxidation variation are consistent with the graphite occurrence within the reduced intervals and the systematic fO2 indicated by olivine V/Sc ratios. Combined with the wide olivine Ni range (200–1500 ppm) and the restricted Ni tenor in coexisting sulfides, those findings imply that the olivine-sulfide interaction was predominantly controlled by fO2. Diffusion modeling at magmatic temperatures reveals that the core-level Fe–Ni re-equilibration after crystallization requires hundreds of years. The homogeneous olivine composition suggests that re-equilibrium has been achieved in Shitoukengde. However, in fast cooling systems, olivine may record the status approaching olivine-sulfide equilibration, leading to extensive intragrain Ni variation (up to 1000 ppm). This study highlights that extreme Ni depletion in olivine from sulfide-bearing rocks is a sign of reducing conditions. Strongly Ni-rich olivine, such as those in the Kevitsa deposit, could result from interaction with high-Ni tenor sulfides at oxidizing conditions.

This paper highlights published and new field and petrographic observations for late-stage (crustal level) deformation associated with the emplacement of kimberlites and other mantle-derived magmas. Thus, radial and tangential joint sets in the competent 183 Ma Karoo basalt wall rocks to the 5 ha. Lemphane kimberlite blow in northern Lesotho have been ascribed to stresses linked to eruption of the kimberlite magma. Further examples of emplacement-related stresses in kimberlites are brittle fractures and close-spaced parallel shears which disrupt olivine macrocrysts. In each of these examples, there is no evidence of post-kimberlite regional tectonism which might explain these features, indicating that they reflect auto-deformation in the kimberlite during or immediately post-emplacement. On a microscopic scale, these inferred late-stage stresses are reflected by fractures and domains of undulose extinction which traverse core and margins of some euhedral and anhedral olivines in kimberlites and olivine melilitites. Undulose extinction and kink bands have also been documented in olivines in cumulates from layered igneous intrusions. Our observations thus indicate that these deformation features can form at shallow levels (crustal pressures), which is supported by experimental evidence. Undulose extinction and kink bands have previously been presented as conclusive evidence for a mantle provenance of the olivines—i.e. that they are xenocrysts. The observation that these deformation textures can form in both mantle and crustal environments implies that they do not provide reliable constraints on the provenance of the olivines. An understanding of the processes responsible for crustal deformation of kimberlites could potentially refine our understanding of kimberlite emplacement processes.

We report the results of experiments designed to separate the effects of temperature and pressure from liquid composition on the partitioning of Ni between olivine and liquid, D Ni ol/liq . Experiments were performed from 1300 to 1600 °C and 1 atm to 3.0 GPa, using mid-ocean ridge basalt (MORB) glass surrounded by powdered olivine in graphite–Pt double capsules at high pressure and powdered MORB in crucibles fabricated from single crystals of San Carlos olivine at one atmosphere. In these experiments, pressure and temperature were varied in such a way that we produced a series of liquids, each with an approximately constant composition (~12, ~15, and ~21 wt% MgO). Previously, we used a similar approach to show that D Ni ol/liq for a liquid with ~18 wt% MgO is a strong function of temperature. Combining the new data presented here with our previous results allows us to separate the effects of temperature from composition. We fit our data based on a Ni–Mg exchange reaction, which yields ln D Ni molar = - Δ r ( 1 ) H T ref , P ref ∘ R T + Δ r ( 1 ) S T ref , P ref ∘ R - ln X MgO liq X MgSi 0.5 O 2 ol . Each subset of constant composition experiments displays roughly the same temperature dependence of D Ni ol/liq (i.e., - Δ r ( 1 ) H T ref , P ref ∘ / R ) as previously reported for liquids with ~18 wt% MgO. Fitting new data presented here (15 experiments) in conjunction with our 13 previously published experiments (those with ~18 wt% MgO in the silicate liquid) to the above expression gives - Δ r ( 1 ) H T ref , P ref ∘ / R  = 3641 ± 396 (K) and Δ r ( 1 ) S T ref , P ref ∘ / R  = − 1.597 ± 0.229. Adding data from the literature yields - Δ r ( 1 ) H T ref , P ref ∘ / R  = 4505 ± 196 (K) and Δ r ( 1 ) S T ref , P ref ∘ / R  = − 2.075 ± 0.120, a set of coefficients that leads to a predictive equation for D Ni ol/liq applicable to a wide range of melt compositions. We use the results of our work to model the melting of peridotite beneath lithosphere of varying thickness and show that: (1) a positive correlation between NiO in magnesian olivine phenocrysts and lithospheric thickness is expected given a temperature-dependent D Ni ol/liq , and (2) the magnitude of the slope for natural samples is consistent with our experimentally determined temperature dependence. Alternative processes to generate the positive correlation between NiO in magnesian olivines and lithospheric thickness, such as the melting of olivine-free pyroxenite, are possible, but they are not required to explain the observed correlation of NiO concentration in initially crystallizing olivine with lithospheric thickness.