Evolution Of Composition Research Articles

Low Temperature and Rapid Synthesis of Li‐Rich Li(Li0.17Mn0.83)2O4 Spinel Cathodes Derived from Metal‐Organic Frameworks for Lithium‐Ion Batteries

AbstractLi‐rich spinel materials (Li1+xMn2−xO4) have shown promise for lithium‐ion batteries. Nevertheless, the preparation of Li1+xMn2−xO4 faces significant challenges due to the difficulty in achieving a balance between well‐crystallized phases and stoichiometric chemistry. Moreover, the synthesis process is highly sensitive to calcination temperature and time, making it susceptible to phase transformations. Therefore, the rational selection of precursors and corresponding calcination procedures is absolutely essential. Herein, we make full use of the nature of metal‐organic frameworks (MOFs) to achieve phase‐controlled synthesis of Li(Li0.17Mn0.83)2O4 (LMO−F) spinel cathodes in 8 minutes at 500 °C. The composition and structural evolution during the pyrolysis process were systematically investigated to clarify the relationship between precursors and derivatives. Notably, the LMO−F achieved good electrochemical performance with 100.4 mAh g−1 at 50 mA g−1 after 100 cycles.

Multiple-wave admixture and adaptive evolution of the Pamirian Wakhi people.

While whole-genome sequencing has been applied extensively to investigate the genetic diversity of global populations, ethnic minority groups in Pakistan are generally underrepresented. In particular, little is known about the genetic origin and highland adaptation of the Pamirian Wakhi people. According to Chinese historical records, the geographical location and language usage of Wakhi may be closely related to Xinjiang Tajiks (XJT). In this study, based on high-coverage (∼30×) whole-genome sequencing of eight Wakhi and 25 XJT individuals, we performed data analyses together with worldwide populations to gain insights into their genetic composition, demography, and adaptive evolution to the highland environment. The Wakhi derived more than 85% of their ancestry from West Eurasian populations (European ∼44.5%, South Asian ∼42.2%) and 10% from East Eurasian populations (Siberian ∼6.0%, East Asian ∼4.3%). Modeling the admixture history of the Wakhi indicated that the early West-East admixture occurred approximately 3,875-2,250 years ago and that the recent admixture occurred 750-375 years ago. We identified selection signatures across EGLN3, in particular, a distinctive evolutionary signature was observed, and a certain underlying selected haplotype showed higher frequency (87.5%) in the Wakhi than in nearby XJT and other highlanders. Interestingly, we found high-frequency archaic sequences in the Wakhi genome, which overlapped with several genes related to cellular signaling transduction, including MAGI2, previously associated with high-altitude adaptation. Our analysis indicates that the Wakhi are distinct from the XJTs and Tajikistan Tajiks, and shed light on the Wakhi's ancestral origin and genetic basis of high-altitude adaptation.

Evolution of Plant Genome Size and Composition.

The rapid development of sequencing technology has led to an explosion of plant genome data, opening up more opportunities for research in the field of comparative evolutionary analysis of plant genomes. In this review, we take changes in plant genome size and composition as a starting point and describe the effects of polyploidy, whole genome duplication and transposable elements changes on plant genome architecture and evolution, respectively. In addition, to address the lack of relevant information in some areas, we also collected and analyzed 234 representative plant genome data as a supplement. We aim to provide a global, up-to-date summary of information on plant genome architecture and evolution in this review.

Structural damage and bubble evolution in SiC-ZrC composite irradiated with 500 keV He-ions at various temperatures

Ceramic composites with high temperature strengths and low neutron cross-sections are promising candidates for core materials in advanced nuclear systems. In present work, SiC-20 vol% ZrC composites were irradiated with 500 keV He-ions at 25, 500 and 800 °C to evaluate the effect of irradiation temperature on the structural damage and bubble evolution in ceramic composites. XRD and Raman spectra analysis give that the irradiation resulted in structural damages of both SiC and ZrC. TEM observations reveal the formation of helium bubbles and defect clusters after irradiation. Moreover, the occurrence of micro-cracks in ZrC grains and amorphization of SiC are observed for the samples irradiated at room temperature. Nanoindentation test showed that there is irradiation induced hardening or softening of the composites which depends on the irradiation temperature or fluence. The correlation between microstructural evolution and mechanical properties response is discussed.

Evolution of pore structure and cement composition during weathering of conglomerate at Mogao Grottoes in alkaline and arid regions, NW China

Numerous conglomerate grottoes have been excavated and preserved in the arid and alkaline regions of NW China. After millennia of weathering, these conglomerate grottoes have suffered from various weathering issues (such as seepage and collapse) that are internally governed by the distribution of pore networks and the degree of cementation. However, studies on conglomerate weathering have mostly been reported in humid and tropical climates, where intensive chemical weathering occurs. Additionally, characterizations of pore evolution during conglomerate weathering have been restricted due to limitations in detecting pore size and pore type using a single pore characterization method. To fill this gap, this study jointly used mercury intrusion porosimetry (MIP) and computed tomography (CT) to characterize the pore evolution process during conglomerate weathering at Mogao Grottoes, a world heritage site in NW China. Mineralogical, hydrological, mechanical and microscopic characterization were also conducted to understand the changes in compositions of bulk samples and cements during weathering. Results revealed that the majority of pores in conglomerate are concentrated in macropores > 5 μm, followed by mesopores and micropores. During weathering, volume fraction of macropores significantly increases and that of micropores decreases, with median/average pore diameters experiencing an 8- to 10-fold increase. Permeability, porosity and fractal dimension exhibited strong positive linear correlations with median/average pore diameters. Throughout weathering, the abundances of calcite and clay minerals show notable decrease, particularly in cements, resulting in an enrichment of feldspars. Frequently occurring sand-carrying wind activities and salt weathering in arid regions are inferred to be responsible for the major cement loss and porosity generation through physical processes. Our combined MIP-CT method for pore network characterization is also applicable to other lithologies with a wide range of pore sizes. The proposed mechanism of pore evolution and cementation failure provides a scientific base for protecting stone heritages in arid zones.

Enhancing the phytoextraction capacity of chromium-contaminated soil by co-addition of garbage enzymes and microelectrolytic iron-carbon fillers

Most improved strategies for phytoextraction do not achieve a synergistic enhancement of chromium (Cr) accumulation capacity and biomass. This study investigated the impacts of co-addition of garbage enzyme (GE) and microelectrolytic iron-carbon filler (MF) on soil physicochemical properties, as well as form and uptake of Cr during aging and phytoextraction process. The response of rhizosphere microbial community to co-addition and its role in enhancing the remediation performance of ryegrass was further analyzed. Co-addition of GE and MF during the 12-day aging process resulted in an increase of nutrients, a shift from an oxidising to a reducing soil environment, a decrease of Cr(VI) content, and an enhancement of soil microbial community diversity and richness, creating a suitable environment for subsequent phytoextraction. During the 40-day phytoextraction process, co-addition played a crucial role in facilitating the establishment of a complex, efficient and interdependent ecological network among soil microorganisms and contributed to the evolution of microbial community composition and functional pathways. An increase in the relative abundance of Trichococcus, Azospirillum and g_norank_f_JG30-KF-CM45 elevated soil nutrient levels, while a decrease in the relative abundance of TM7a and Brucella reduced pathogen harbouring. Meanwhile, co-addition increased the relative abundance of Bacillus, Arthrobacter and Exiguobacterium, attenuated Cr phytotoxicity and improved soil biochemical activity. These markedly diminished oxidative damage and improved ryegrass growth by reducing malondialdehyde accumulation. In addition, regular additions of GE and the increase in relative abundance of norank_fnorank_o_Microtrichales led to rhizosphere acidification, which inhibited short-term Cr immobilization and contributed to a notable increase in phytoextraction efficiency. This study presents a strategy to enhance phytoremediation efficiency and soil quality during phytoextraction of Cr-contaminated soils.

Bio-inspired widening concrete using cellulose nanofiber to enhance multiscale Fiber–Matrix interface

The cracking issue at the bonded interface due to the differing shrinkage performances of newly poured concrete and existing concrete poses a significant threat to the safe service of composite structures. Inspired by the musculoskeletal system, we propose the use of multiscale hybrid reinforced concrete materials, incorporating basalt fiber (BF), polypropylene (PP) fiber, and cellulose nanofiber (CNF), for bridge widening structures. Experimental investigations were carried out to assess the bond splitting tensile strength, diagonal shear strength, crack resistance, development of drying shrinkage deformation, and the propagation behavior of restrained shrinkage-induced cracks in both new and old concrete reinforced with single and hybrid combinations of BF, PP fiber, and CNF. The microstructure, phase composition, and pore structure evolution of BF, PP fiber, and CNF-reinforced concrete were observed and analyzed using scanning electron microscopy, thermogravimetric and derivative thermogravimetric analysis, nuclear magnetic resonance, and mercury intrusion porosimetry. The results indicate that the incorporation of BF, PP fiber, and CNF exhibits excellent synergistic effects, improving the bond and shrinkage performance of the concrete interface. As the CNF content increases, the macro fiber–matrix interface improves. This bio-inspired work will contribute to the development of strong, tough, and sustainable concrete for bridge widening structures.

The mid-Cretaceous Hohonu Batholith (South Island, New Zealand): Identifying magmatic sources and processes during onset of crustal extension

The Hohonu Batholith is an aggregation of mostly mid-Cretaceous granitoid plutons on the West Coast of the South Island of New Zealand emplaced during a transitional period between subduction-related compression and continental lithospheric extension. This study reports an integrated dataset, comprising in-situ UPb, O and Hf isotope compositions and REE, Ti and other trace and major elements (ZrHf, ThU) for zircons extracted from four representative plutons within the batholith. Our results provide detailed insight into the protracted thermal, chronological and geochemical histories. LA-ICPMS UPb zircon ages indicate a primary episode of magma genesis and emplacement from 107 to 113 Ma, confirming published SIMS dating. However, a younger previously unrecognized age population of ~91–96 Ma is identified, primarily (although not exclusively) in zircon rims. This younger age event coincides with the timing of protracted lithospheric extension and crustal thinning of the Zealandia continent. The cryptic younger zircon ages suggest that Hohonu granitoids experienced a partial thermal overprint (accompanied by Pb loss) mostly recorded in rims. Differences in bulk rock geochemistry between plutons are inferred to reflect variable conditions of partial melting controlled by source mineralogy and H2O content. Isotope and trace element compositions, along with Ti-thermometry, measured on the same micro-volume of CL-imaged zircons, are used to test if source characteristics were imparted from melt to minerals in zircon-saturated silicic systems. Similarities are revealed in the zircon record of the selected plutonic rocks, confirming their broadly consanguineous relationship and the fundamental role of open-system behaviour, involving hybridization or assimilation between mantle-derived (or juvenile mafic) and a crustal-derived components, as previously inferred from whole rock NdSr isotope systematics. However, intra-sample decoupling of zircon OHf isotope systematics may also be linked to residual source component unmixing. This possibility, in addition to mafic recharge, may have obscured melt source compositional characteristics, and hence zircon REE appear as unsuitable fingerprints of source(s) and conditions of partial melting in this granitoid system. Simple compositional and thermal magma evolution trends appear punctuated by episodes of mafic recharge, presumably during lithospheric thinning.

TeO[formula omitted]–BaO–Bi[formula omitted]O[formula omitted] tellurite optical glasses I. - Glass formation, structural, thermal and optical properties

The present study investigates the glass-forming ability (GFA), structural, thermal, and optical properties of the TeO2–BaO–Bi2O3 (TeBaBi) glass system, focusing on the mutual substitution trends of its constituent compounds. Prepared glasses were synthesized by the melt-quenching method at 900 °C and the GFA was extended by chemical compositions with lower TeO2 (55–85 mol.%) and higher Bi2O3 (5–15 mol.%) content via optimization of the synthesis process. The introduction of BaO and/or Bi2O3 results in the increase of the glass transition temperature (Tg≈327–384°C), molar volume (Vg≈28.9–33.1cm3mol−1) and optical basicity (OB≈0.97–1.03). Prepared TeBaBi glasses exhibit satisfactory thermal stability and wide spectral region of optical transparency from 0.4–6.5 μm with observed narrowing of optical window with higher TeO2 content. Compositional evolution of Tg may be described for the TeBaBi glasses using multilinear regression analysis with high correlation (r≥0.995) across the whole GFA region. The structure of studied TeBaBi glasses was investigated by Raman scattering and directly compared to the TeO2–ZnO–BaO (TZB) glass system prepared and characterized under identical conditions. Structural analysis revealed a similar degree of internal glass structure transformation regardless of whether a divalent zinc cation or trivalent bismuth cation is present.

Moiré-regulated composition evolution kinetics of bicomponent nanoclusters

Moiré-regulated composition evolution kinetics of bicomponent nanoclusters

Spatially resolved plasma composition evolution in a solar flare – The effect of reconnection outflow

Context. Solar flares exhibit complex variations in elemental abundances compared to photospheric values. These abundance variations, characterized by the first ionization potential (FIP) bias, remain challenging to interpret. Aims. We aim to (1) examine the spatial and temporal evolution of coronal abundances in the X8.2 flare on 2017 September 10, and (2) provide a new scenario to interpret the often observed high FIP bias loop top, and provide further insight into differences between spatially resolved and Sun-as-a-star flare composition measurements. Methods. We analyzed 12 Hinode/Extreme-ultraviolet Imaging Spectrometer (EIS) raster scans spanning 3.5 hours, employing both Ca XIV 193.87 Å/Ar XIV 194.40 Å and Fe XVI 262.98 Å/S XIII 256.69 Å composition diagnostics to derive FIP bias values. We used the Markov Chain Monte Carlo (MCMC) differential emission measure (DEM) method to obtain the distribution of plasma temperatures, which forms the basis for the FIP bias calculations. Results. Both the Ca/Ar and Fe/S composition diagnostics consistently show that flare loop tops maintain high FIP bias values of > 2–6, with peak phase values exceeding 4, over the extended duration, while footpoints exhibit photospheric FIP bias of ∼1. The consistency between these two diagnostics forms the basis for our interpretation of the abundance variations. Conclusions. We propose that this variation arises from a combination of two distinct processes: high FIP bias plasma downflows from the plasma sheet confined to loop tops, and chromospheric evaporation filling the loop footpoints with low FIP bias plasma. Mixing between these two sources produces the observed gradient. Our observations show that the localized high FIP bias signature at loop tops is likely diluted by the bright footpoint emission in spatially averaged measurements. The spatially resolved spectroscopic observations enabled by EIS prove critical for revealing this complex abundance variation in loops. Furthermore, our observations show clear evidence that the origin of hot flare plasma in flaring loops consists of a combination of both directly heated plasma in the corona and from ablated chromospheric material; and our results provide valuable insights into the formation and composition of loop top brightenings, also known as EUV knots, which are a common feature at the tops of flare loops.

Isotopic composition of natural waters of Kuzbass in coalbed methane production areas

Relevance. In Kuzbass, a coalbed methane production project is being implemented for the first time in Russia. Formation water extracted together with coalbed methane plays an important role, since it has been in contact with the coal-bearing rocks for a long time, therefore it contains rich geochemical information. Over the period 2002–2022, new isotopic data were accumulated both on the waters of the region coal deposits and on overlying waters, including surface waters. Aim. Based on the material accumulated on the isotopic composition (δD, δ18O, δ13C, 34S, 3H, 14C) of natural waters in coal-bearing areas, create an evolutionary scheme for the formation of waters within the framework of the developed hypothesis on the interaction of water-rock-coal-methane. Objects. River, underground waters of the zone of active water exchange, upper and lower parts of the zone of slow water exchange (extracted together with coalbed methane). Methods. Studies of the isotopic composition of waters were carried out in several laboratories: in the Multielement and Isotope Research Center of the SB RAS, the Technical Branch of the Federal State Unitary Enterprise “SNIIGGIMS”, in the radiocarbon AMS laboratory based on the Center for Collective Use “Cenozoic Geochronology” and in the Pacific Oceanological Institute Far Eastern Branch Russian Academy of Sciences (POI) FEB RAS. Results and conclusions. The paper introduces the data on δD, δ18О, δ13С и δ34S for surface and groundwater in Kuzbass in coalbed methane production areas. It is shown that all the waters under consideration are infiltration based on their isotopic composition (δD and δ18О). The waters of the lower part of the slow water exchange, produced together with coalbed methane, are characterized by a positive oxygen shift and very light hydrogen. A diagram of the evolution of the isotopic composition of water-dissolved carbon in the region has been compiled according to the data obtained. It is noted that the atmospheric source of CO2 is characteristic only of river waters, and only biogenic carbon dioxide is present in groundwater. The wide range of δ13СDIC values of the latter is explained by the varying degrees of participation of light soil carbon dioxide and heavy biochemical carbon dioxide formed during methane formation in the coal seam. The heaviest values are typical for waters produced together with coalbed methane, which is associated with long-term interaction with coal and methane. The time of such interaction was determined using the radiocarbon method: 17–30 thousand years. In areas where coalbed methane is produced, an increase in δ13СDIC values for all natural waters is observed, which requires further study.

Development of craquelure patterns in paintings on canvas

Canvas paintings are layered structures composed of canvas support sized with animal glue, a preparatory layer of the ground, and paint and varnish layers on the top. Preventing or limiting humidity-induced stresses in these structures requires an understanding of the relevant processes and risks. A three-dimensional model of a canvas painting was used to analyse stresses and crack development in the two-layer structure comprised of a glue-sized canvas on a wooden stretcher with a layer of stiff chalk-glue ground representing a pictorial layer in historic canvas paintings. The model was subjected to a large relative humidity fall which induced shrinkage of the glue-sized canvas. The modelling revealed that when a stretcher with flexible wooden bars is considered, high tensile stresses arise in the ground layer at the corners of the painting, and cracks are formed in these areas in the direction perpendicular to the painting’s diagonal. Ratios of critical distances between cracks to the ground layer thickness for which stresses in the midpoints between the cracks dropped to below the level inducing fracture in the material were estimated for various magnitudes of the relative humidity drop and thicknesses of the ground layer. Increasing ground layer thickness limits the hygric response of the sized canvas and makes the paintings less vulnerable to humidity variations. The ratio of stress along the diagonal calculated for painting with one crack to the solution without cracks was described by the double Lorentz function. A simple procedure of calculating stress variations along the diagonal—using the function—on a sequential addition of cracks was developed. Cracks in central parts of canvas painting were found to be induced by permanent cumulative drying shrinkage of the oil-based paints and grounds due to the evolution of the molecular composition of the oil binder. The outcome of the modelling indicated that the risk of cracking of the pictorial layers in canvas paintings due to drops in ambient relative humidity was small.

The evolution of carotid atherosclerotic plaque composition: a prospective study

Abstract Background The rupture of carotid atherosclerotic plaque is one of the major causes of ischemic stroke, and largely determined by the composition of the plaque. To date, most studies on carotid plaque composition focused on individual plaque components, whilst the interplay between different components within the same plaque may be a critical driving force for plaque evolution and rupture. Objectives To determine the interplay between carotid plaque components over time and describe the dynamics of plaque composition with a specific focus on age- and sex-specific changes in a population-based setting. Methods From a population-based cohort in Netherlands, 802 participants (mean age ± SD 68 ± 8 years, 43% women) with subclinical carotid atherosclerosis underwent repeat magnetic resonance imaging (MRI) of carotid plaque (first scan between 2007 and 2012, second scan between 2014 to 2017). We evaluated carotid plaque composition, including calcification, lipid-rich necrotic core (LRNC) and intraplaque hemorrhage (IPH). To assess the relationship between the incidence of one specific component and baseline plaque composition, plaques with this specific component present at the baseline were excluded. Generalized estimation equation models were used with adjustments for baseline plaque size and cardiovascular risk factors. We demonstrated the evolution of plaque composition along age and by sex. Results Baseline presence of calcification in carotid plaque is independently associated with a higher incidence of IPH (adjusted odds ratio: 2.25; 95% confidence interval: 1.40 to 3.63). No associations were found between baseline plaque composition and the new onset of calcification or LRNC. The proportion of complex plaques with multiple components significantly increased at follow-up (Figure 1a). The plaque composition dramatically evolved over time and the proportion of plaques with two or more components started with 10% around 55 years and increased to over 50% after 70 years of age (Figure 1b). Although the age distribution was comparable between men and women, men were more likely to have and develop plaques with multiple vulnerable plaque components such as IPH (Figure 2). Conclusions A higher incidence of IPH was found in plaques with baseline calcification. The pre-existing plaque composition strongly determines how the plaque will evolve over time. Given the interplay between individual components, the overall plaque composition exhibits significant age- and sex- specific characteristics.

Multifunctional highly conductive cellulose nanopaper with ordered PEDOT:PSS alignment enabled by external surface area-promoted phase separation

Integrating cellulose, the most abundant biopolymer on Earth, with PEDOT:PSS, the most commercially available conducting polymer, can create multifunctional conductive nanopapers for sustainable electronics. However, conventional PEDOT:PSS/cellulose composites often exhibit limited conductivity, primarily due to the random distribution of PEDOT and the aggregation of PSS within the cellulose matrix. Herein, we introduce a confined phase separation approach that leverages the inherent physical characteristics of the cellulose substrate to enhance the performance of these composites. By systematically investigating the influence of the external surface area of nanocellulose on PEDOT:PSS coverage and composition evolution, we demonstrate that a higher external surface area ensures uniform PEDOT:PSS coating on nanocellulose networks and facilitates effective PSS removal during secondary doping. This process enhances phase separation and promotes ordered alignment of PEDOT chains along nanocellulose, resulting in an electrical conductivity of up to 252 S cm−1. Such highly conductive nanopapers exhibit exceptional performances in supercapacitors and electromagnetic shielding, achieving an ultrahigh specific electromagnetic shielding effectiveness of 33,122 dB cm2 g⁻1 at only 6 μm thickness. Our study highlights the critical role of cellulose substrate selection at the nanoscale and elucidates the interactions within conducting polymers, offering a promising pathway for developing high-performance, sustainable electronics.

Carbon Nanoparticle Oxidation by NO2and O2: Chemical Kinetics andReaction Pathways.

Carbon nanoparticle interactions with gases are central to many environmental and technical processes, but the underlying reaction kinetics and mechanisms are not well understood. Here, we investigate the oxidation and gasification of carbon nanoparticles by NO2and O2under combustion exhaust conditions. We build on a comprehensive experimental data set and use a kinetic multilayer model (KM-GAP-CARBON) to trace the uptake and release of gas molecules alongside the temporal evolution of particle size and surface composition. The experimental results are captured by a model mechanism that involves different types of carbon atoms (edge/plane-like) and the formation of a reactive oxygen intermediate (activated CO complex) as the rate-limiting step. A transition between distinct chemical regimes driven by NO2at lower temperatures and O2at higher temperatures is reflected by an increase in the observable activation energy from ~60 kJ/mol to ~130 kJ/mol. We derive energy profiles for three alternative reaction pathways that involve uni- or bimolecular decomposition of reactive oxygen intermediates.

Carbon Nanoparticle Oxidation by NO2 and O2: Chemical Kinetics and Reaction Pathways

Carbon nanoparticle interactions with gases are central to many environmental and technical processes, but the underlying reaction kinetics and mechanisms are not well understood. Here, we investigate the oxidation and gasification of carbon nanoparticles by NO2 and O2 under combustion exhaust conditions. We build on a comprehensive experimental data set and use a kinetic multilayer model (KM‐GAP‐CARBON) to trace the uptake and release of gas molecules alongside the temporal evolution of particle size and surface composition. The experimental results are captured by a model mechanism that involves different types of carbon atoms (edge/plane‐like) and the formation of a reactive oxygen intermediate (activated CO complex) as the rate‐limiting step. A transition between distinct chemical regimes driven by NO2 at lower temperatures and O2 at higher temperatures is reflected by an increase in the observable activation energy from ~60 kJ/mol to ~130 kJ/mol. We derive energy profiles for three alternative reaction pathways that involve uni‐ or bimolecular decomposition of reactive oxygen intermediates.

Phase equilibrium constraints on the pre-eruptive conditions of alkaline basalts of the Main Ethiopian Rift and their bearing on the production of peralkaline rhyolites

Abstract Bimodal magmatism is characteristic of the geodynamic evolution of the Main Ethiopian Rift (MER), which is a reference area for the study of the processes leading to continental break-up before seafloor spreading. There are abundant emissions of basalts and rhyolites, which are in possible parent-daugther relationships. However, the P-T-H2O conditions of production and storage of the basaltic end member remain unclear. Crystallization experiments have been conducted on an alkali basalt from the MER to define its pre-eruptive conditions and shed light on the compositional evolution of derivative liquids and source conditions. The experiments were performed at 100-200 MPa, 975-1080°C, varying H2O/CO2 ratios, corresponding to melt water contents of 1-5 wt%, at fO2 slightly lower than the Fayalite-Magnetite-Quartz (FMQ) solid buffer. Comparison between the petrological attributes of the starting rock and the experiments shows that the basaltic magma was stored at 150-200 MPa, 1050 ± 10°C, with 1-2 wt% H2O in melt, with fO2 near FMQ prior to eruption. Geochemical modelling shows that the corresponding mantle source contained about 0.1 wt% H2O, reflecting a metasomatized source. Extensive crystallization of such basalts produces SiO2-rich liquids, which are not yet peralkaline, however. This underscores that extreme fractionation (>90 wt%) is required in order to produce peralkaline derivatives from mildly alkaline basalts. This extreme fractionation and the water-rich nature of the starting basalt readily explain the H2O-rich condition of peralkaline rhyolites that have fueled caldera forming eruptions in the Rift.

RocMLMs: Predicting Rock Properties Through Machine Learning Models

AbstractMineral phase transformations significantly alter the bulk density and elastic properties of mantle rocks and consequently have profound effects on mantle dynamics and seismic wave propagation. These changes in the physical properties of mantle rocks result from evolution in the equilibrium mineralogical composition, which can be predicted by the minimization of the Gibbs Free Energy with respect to pressure (P), temperature (T), and chemical composition (X). Thus, numerical models that simulate mantle convection and/or probe the elastic structure of the Earth's mantle must account for varying mineralogical compositions to be self‐consistent. Yet coupling Gibbs Free Energy minimization (GFEM) approaches with numerical geodynamic models is currently intractable for high‐resolution simulations because prediction speeds of widely‐used GFEM programs (100–102 ms) are impractical in many cases. As an alternative, this study introduces machine learning models (RocMLMs) that have been trained to predict thermodynamically self‐consistent rock properties at arbitrary PTX conditions between 1–28 GPa and 773–2,273 K, and dry mantle compositions ranging from fertile (lherzolitic) to refractory (harzburgitic) end‐members define9d with a large data set of published mantle compositions. RocMLMs are 101–103 times faster than GFEM calculations or GFEM‐based look‐up table approaches with equivalent accuracy. Depth profiles of RocMLMs predictions are nearly indistinguishable from reference models PREM and STW105, demonstrating good agreement between thermodynamic‐based predictions of density, Vp, and Vs and geophysical observations. RocMLMs are therefore capable, for the first time, of emulating dynamic evolution of density, Vp, and Vs due to partial melting and refertilization of dry mantle rocks in high‐resolution numerical geodynamic models.

Underplating-induced trans-crustal melting and maturation of Neoarchean continental crust in the North China Craton

A global change in granitoid compositions from early predominantly sodic tonalite-trondhjemite-granodiorites (TTGs) to later TTGs and more potassic granites occurred during the late Archean, coupled with a major period of crustal maturation. However, the detailed relationship between granitoid chemical evolution and the maturing crustal process remains enigmatic. Successive granitoid magmatism including late Neoarchean TTGs and high-K granites occurred in the Western Shandong Province granite-greenstone belt (WSP) of the North China Craton and thus preserves crucial clues of the crustal maturation process. In this study, petrology, whole-rock geochemistry, and zircon U-Pb and Lu-Hf isotopes are reported for the late Neoarchean TTG gneisses, monzogranites, and minor metabasaltic to andesitic rocks from the WSP. The ca. 2560−2540 Ma TTG gneisses show low MgO, K2O/Na2O, but high (La/Yb)N, Sr/Y, and absence of Eu anomalies, indicating their derivation from partial melting of the thickened lower mafic crust. The ca. 2530−2500 Ma monzogranites are characterized by systematically high SiO2 and K2O/Na2O, but low MgO and Sr/Y, and moderately negative Eu anomalies, revealing they were formed by intracrustal reworking of local TTGs and sedimentary rocks in the middle to upper crust. Geochemical variations of these crustal-derived granitoids suggest that they were formed by melting at gradually higher crustal levels with the melt zone moved gradationally from the eclogite stability field into the plagioclase stability field. The ca. 2530−2500 Ma calc-alkaline metabasaltic to andesitic rocks sourced from metasomatized mantle outline roles of mantle-derived magma underplating in contributions of heating and trans-crustal melting magmatism. The long-term melting processes facilitated the upward movement of volatiles and heat-producing elements from deep to shallow crustal levels, and introduced K-enriched monzogranites into the upper crust, leaving a refractory, strengthening, and tectonically stable lower crust. Secular compositional evolution of crustal-derived granitoids reveals that continuous crustal reworking drove lithosphere differentiation and paved the way for the maturation of the Archean continental crust.