Principle of Hydrogen Isotope Geochemistry Paleo-altimeter and its Potential in Reconstructing Paleo-elevation of the Southeastern Tibetan Plateau

The reconstruction of paleo-elevation serves a dual purpose to enhance our comprehension of geodynamic processes affecting terrestrial landforms and to contribute significantly to the interpretation of atmospheric circulation and biodiversity.The oxygen(δ~(18)O_w)and deuterium(δD_w)isotopes in atmospheric precipitation are systematically depleted with the increase of altitude,which are typical and widely applicated paleo-altimeters.The utilization of hydrogen isotope of hydrous silicate minerals within the shear zone system,volcanic glass,and plant leaf wax alkanes offers valuable insights for addressing evaporation and diagenesis.In this paper,we review the principle,application conditions,and influencing factors of the hydrogen isotope paleo-altimeter.In addition,we discuss the feasibility of utilizing this technique for quantitatively estimating the paleo-elevation of the southeastern Tibetan Plateau,where multiple shear zones extend over hundred kilometers parallel to the topographic gradient.

Hydrocarbon Generation Characteristics of Coal-measure Source Rocks and their Contribution to Natural Gas:A Case Study of Middle and Lower Jurassic Targets from the Southern Junggar Basin Margin

In order to study the hydrocarbon generation(HCGE)characteristics of coal-bearing basins,the coal-measure source rocks of the Middle Jurassic-Lower Jurassic(MLJ)of the piedmont thrust belt in the southern margin of the Junggar Basin in Northwest China are taken as research objects.More than 60 MLJ samples were collected from outcrops and wells.Total organic carbon(TOC),rock pyrolysis(Rock-Eval),organic petrological,vitrinite reflectance(%Ro),and hydrous pyrolysis were performed to analyze the relevant samples.The pyrolysis gases and liquid products were measured,and then the chemical composition,as well as carbon isotopes of the gases,were analyzed.The results indicate that the MLJ source rocks have the capacity for large-scale gas generation.In addition,for coal-measure source rocks,the heavier the carbon isotope of kerogen(δ^(13)C_(kerogen)),the lower the liquid hydrocarbon and hydrocarbon gas yield,and the easier it is to produce non-hydrocarbon gas.It is worth noting that when theδ^(13)C_(kerogen)in organic matter(OM)is relatively heavier,the fractionation of its products may become weaker in the evolutionary process.The vital contribution of the MLJ source rock to natural gas resources in the study area was further confirmed by comparing it with the Jurassic source gas.

High-Power and Ultralong-Life Aqueous Zinc-Ion Hybrid Capacitors Based on Pseudocapacitive Charge Storage

Rechargeable aqueous zinc-ion hybrid capacitors and zincion batteries are promising safe energy storage systems.In this study,amorphous RuO2·H2O for the first time was employed to achieve fast and ultralong-life Zn2+storage based on a pseudocapacitive storage mechanism.In the RuO2·H2O||Zn zinc-ion hybrid capacitors with Zn(CF3SO3)2 aqueous electrolyte,the RuO2·H2O cathode can reversibly store Zn2+in a voltage window of 0.4-1.6 V(vs.Zn/Zn2+),delivering a high discharge capacity of 122 mAh g?1.In particular,the zinc-ion hybrid capacitors can be rapidly charged/discharged within 36 s with a very high power density of 16.74 kW kg?1 and a high energy density of 82 Wh kg?1.Besides,the zinc-ion hybrid capacitors demonstrate an ultralong cycle life(over 10,000 charge/discharge cycles).The kinetic analysis elucidates that the ultrafast Zn2+storage in the RuO2·H2O cathode originates from redox pseudocapacitive reactions.This work could greatly facilitate the development of high-power and safe electrochemical energy storage.

The Impact of Aqueous Medium on Gas Yields and Kinetic Behaviors of Hydrogen Isotope Fractionation during Organic Matter Thermal Degradation

In order to recognize the impact of aqueous medium on gas yields and the kinetic behaviors of hydrogen isotope fractionation during organic matter thermal degradation, the gold tube apparatus was used to conduct thermal simulation experiments by mixing the nC18 with the water of different properties and proportions. The yields of natural gas components, the relation among hydrogen isotope composition of each component and the experimental temperatures vs. heating rates have been obtained, and the results indicate that under the higher temperature conditions, the hydrous experiment has obvious impact on gas yields, such as when more water is added, higher amounts of hydrocarbon gas and H2 are yielded, and the existence of water obviously prolongs the temperature interval with the existence of heavy hydrocarbon gas. It also shows that the hydrogen isotope of hydrocarbon gas generated by the hydrous experiment is obviously lighter than that generated by the anhydrous experiment, and with the increasing amount of added water, the δD value of hydrocarbon gas gradually decreases. Compared with gas yields, the variation of δD value is more sensitive to aqueous medium in the thermal simulation experiment. However, compared with the amount of the added water, the aqueous medium property has smaller impact on the gas yields, which still shows the inherit effect on hydrogen isotope composition of aqueous medium. Through the model simulation and the isotope fractionation behavior analysis, it is validated that the hydrogen isotope fractionation process can be well described by the chemical kinetic model. The difference of reaction fraction of normal methane and D-containing methane is large, corresponding to the same activation energy. The content of normal methane is obviously higher in the part with lower activation energy, while the content of D-containing methane is higher in the part with higher activation energy. Therefore, it will result in larger hydrogen isotope fractionation amplitude, and the δD values will be more sensitive to the variation of maturity. Meanwhile, the average activation energy of methane generation from nC18 in the hydrous experiment is higher than that in the anhydrous experiment, and the greater amount of added water, the larger the average activation energy of methane generation reaction. This has laid foundation for its exploratory application in the study of gas reservoir forming history and the gassource correlation, which indicates the research and application prospects in this orientation.

Column adsorption of Cu(Ⅱ) by polymer-supported nano-iron oxides in the presence of sulfate: Experimental and mathematical modeling

Polymer-supported hydrous iron oxides(HFOs) are promising for heavy metals removal from aqueous systems.The ubiquitous inorganic ligands, e.g., sulfate, are expected to exert considerable impacts on pollutants removal by these hybrid sorbents. Herein, we obtained a hybrid sorbent HFO-PS by encapsulating nanosized HFO into macroporous polystyrene(PS) resin. Both batch and column sorption experiments of Cu(Ⅱ) by HFO-PS were carried out in the presence of sulfate. Obviously, the presence of sulfate is favorable for Cu(Ⅱ) sorption onto HFO-PS.The performances of column Cu(Ⅱ) removal were fitted and predicted with Adams–Bohart, Clark, Thomas and BDST models. Thomas model is suggested best-fit to predict the breakthrough curves. Besides, a linear correlation is observed between breakthrough time and column length based on BDST model, which might be useful for predicting the breakthrough time for Cu(Ⅱ) removal by HFO-PS.

Effects of U-ore on the chemical and isotopic composition of products of hydrous pyrolysis of organic matter

In order to investigate the impact of U-ore on organic matter maturation and isotopic fractionation,we designed hydrous pyrolysis experiments on Type-II kerogen samples,supposing that the water and water–mineral interaction play a role.U-ore was set as the variable for comparison.Meanwhile,anhydrous pyrolysis under the same conditions was carried out as the control experiments.The determination of liquid products indicates that the presence of water and minerals obviously enhanced the yields of C（15＋） and the amounts of hydrocarbon and nonhydrocarbon gases.Such results may be attributed to waterorganic matter reaction in the high-temperature system,which can provide additional hydrogen and oxygen for the generation of gas and liquid products from organic matter.It is found that δD values of hydrocarbon gases generated in both hydrous pyrolysis experiments are much lower than those in anhydrous pyrolysis.What is more,δD values are lower in the hydrous pyrolysis with uranium ore.Therefore,we can infer that water-derived hydrogen played a significant role during the kerogen thermal evolution and the hydrocarbon generation in our experiments.Isotopic exchange was facilitated by the reversible equilibration between reaction intermediaries with hydrogen under hydrothermal conditions with uranium ore.Carbon isotopic fractionations of hydrocarbon gases were somehow affected by the presence of water and the uranium ore.The increased level of i-C4/n-C4ratios for gas products in hydrous pyrolysis implied the carbocation mechanism for water-kerogen reactions.

Melting of hydrous pyroxenites with alkali amphiboles in the continental mantle:1.Melting relations and major element compositions of melts

Melting experiments on ultramafic rocks rich in the hydrous minerals phlogopite or phlogopite+K-rich terite,some including 5%of accessory phases,have been conducted at 15 and 50 kbar.The assemblages represent probable source components that contribute to melts in cratonic regions,but whose melt compositions are poorly known.A main series of starting compositions based on MARID xenoliths consisted of a third each of clinopyroxene(CPX),phlogopite(PHL)and K-richterite(KR)with or without 5%ilmenite,rutile or apatite.Additional experiments were run without KR and with higher proportions of accessory phases.Melt traps were used at near-solidus temperatures to facilitate accurate analysis of wellquenched melts,for which reversal experiments demonstrate equilibrium.Results show that KR melts rapidly and completely within 50°C of the solidus,so that melts reflect the composition of the amphibole and its melting reaction.Melts have high SiO_(2) and especially K_(2)O but low CaO and Al_(2)O_(3) relative to basaltic melts produced from peridotites at similar pressures.They have no counterparts amongst natural rocks,but most closely resemble leucite lamproites at 15 kbar.KR and PHL melt incongruently to form olivine(OL)and CPX at 15 kbar,promoting SiO2 contents of the melt,whereas orthopyroxene OPX is increasingly stable at lower lithosphere pressures,leading to an increase in Mg O and decrease in SiO_(2) in melts,which resemble olivine lamproites.Melts of mica pyroxenites without KR are richer in CaO and Al_(2)O_(3) and do not resemble lamproites.These experiments show that low CaO and Al_(2)O_(3) in igneous rocks is not necessarily a sign of a depleted peridotite source.Accessory phases produce melts exceptionally rich in P_(2)O_(5) or TiO_(2) depending on the phases present and are unlike any melts seen at the Earth’s surface,but may be important agents of metasomatism seen in xenoliths.The addition of the 5%accessory phases ilmenite,rutile or apatite result in melting temperatures a few ten of degrees lower;at least two of these appear essential to explain the compositions of many alkaline igneous rocks on cratons.Melting temperatures for CPX+PHL+KR mixtures are close to cratonic geotherms at depths>130 km:minor perturbations of the stable geotherm at>150 km will rapidly lead to 20%melting.Melts of hydrous pyroxenites with a variety of accessory phases will be common initial melts at depth,but will change if reaction with wall-rocks occurs,leading to volcanism that contains chemical components of peridotite even though the temperature in the source region remains well below the melting point of peridotite.At higher temperatures,extensive melting of peridotite will dilute the initial alkaline melts:this is recognizable as alkaline components in basalts and,in extreme cases,alkali picrites.Hydrous pyroxenites are,therefore,components of most mantle-derived igneous rocks:basaltic rocks should not be oversimplified as being purely melts of peridotite or of mixtures of peridotite and dry pyroxenite without hydrous phases.

Measurements of Enthalpy Change of Reaction of Formation, Molar Heat Capacity and Constant-Volume Combustion Energy of Solid Complex Yb(Et_2dtc)_3(phen)

A ternary solid complex Yb（Et2dtc）3（phen） was obtained from the reaction of hydrous ytterbium chloride with sodium diethyldithiocarbamate （NaEt2dtc）, and 1, 10-phenanthroline （o-phen·H2O） in absolute ethanol. The bonding characteristics of the complex were characterized by IR. The result shows Yb3^＋ bands with two sulfur atoms in the Na（Et2dtc）3 and two nitrogen atoms in the o-phen. The enthalpy change of liquid-phase reaction of formation of the complex △rHm^θ（Ⅰ）, was determined as being （-24.838±0.114） kJ·mol^-1 at 298.15 K, by an RD-496 Ⅲ type heat conduction microcalormeter. The enthalpy change of the solid-phase reaction of formation of the complex △rHm^θ（s）, was calculated as being （108.015±0.479） kJ·mol^-1 on the basis of an appropriate thermochemistry cycle. The thermodynamics of liquid-phase reaction of formation of the complex was investigated by changing the temperature during the liquid-phase reaction. Fundamental parameters, the activation enthalpy, △H≠^θ, the activation entropy, △S≠^θ, the activation free energy,△G≠^θ, the apparent reaction rate constant k, the apparent activation energy E, the pre-exponential constant A, and the reaction order n, were obtained by a combination of the reaction thermodynamic and kinetic equations with the data from the thermokinetic expenments. At the same time, the molar heat capacity of the complex cm. p, Was determined to be （86.34± 1.74） J·mol^-1·K^-1 by the same microcalormeter. The constant-volume combus- tion energy of the complex, △cU, was determined to be （ - 17954.08 ± 8.11） kJ·mol^-1 by an RBC-Ⅱ type rotating-bomb calo- rimeter at 298.15 K. Its standard enthalpy of combustion, △cHm^θ, and standard enthalpy of formation, △fHm^θ, were calculated to be （- 17973.29±8.11） kJ·mol^-1 and （-770.36±9.02） kJ·mol^-1, respectively.

Towards storable and durable Zn-MnO_(2) batteries with hydrous tetraglyme electrolyte

Aqueous rechargeable zinc-based batteries have attracted increasing interest and been considered potential alternatives for state-of-the-art lithium-ion batteries because of the low cost and high safety.Many cathode materials have been gradually developed and demonstrated excellent electrochemical performances.However,the complex electrochemistry,inevitable hydrogen release,and zinc corrosion severely hinder the practical application.The most concerned Zn-MnO_(2)batteries still suffer from the Mn dissolution and formation of byproducts.By adding organic solvents to inhibit the activity of water molecules,the hydrous organic electrolytes provide a sound solution for eliminating the unfavorable factors.Here we report a tetraethylene glycol dimethyl ether-based hydrous organic electrolyte consisting of LiClO_(4)·3H_(2)O and Zn(ClO4)2·6H2O,and a birnessite-type MnO_(2)cathode material for Zn-MnO_(2)batteries.The Li+/Zn2+ions co-(de)insertion mechanism is ascertained by the structural and morphological analyses.The electrostatic interaction between inserted ions and crystal structure is reduced effectively by employment of monovalent Li+ions,which ensures structural stability of cathode materials.Hydrous tetraglyme electrolyte inhibits the activity of water molecules and thus avoids the formation of byproduct Zn_(4)ClO_(4)(OH)7·Meanwhile,highly stable Zn plating/stripping for over 1500 h,an average coulombic efficiency of>99%in long-term cycling,and ultralong storage life(the cells can work well after stored over 1 year)are simultaneously realized in the novel electrolyte.Benefitting from these aspects,the Zn-MnO_(2)batteries manifest high specific capacity of 132 mA h g^(-1),an operating voltage of 1.25 V,and a capacity retention of>98%after 1000 cycles at a current density of 200 mA g^(-1).

A novel supercapacitor-fuel cell hybrid cell

A monolithic hybrid fuel cell (MHFC) with a novel configuration was proposed in an effort to improve the fuel cell performance during instantaneous power changes. A modified direct methanol fuel cell (DMFC) with a layer of hydrous ruthenium dioxide (RuO2·xH2O) sandwiched between the anode catalyst layer and membrane was used to demonstrate the principle of the MHFC. Experimental results indicate that the RuO2·xH2O layer is equivalent to a resistor-capacitor transmission line and functions similar to a capacitor in parallel with the anode electrode. The improvement in dynamic response of the MHFC was experimentally confirmed under step current change and square current pulse operating. The ionic conductivity of the RuO2·xH2O layer was also obtained.

Experimental Study of the Influence of Hydrous Minerals on the Melting Behaviour of Rocks at High Temperatures and Pressures

The experimental study on the melting of potassic basalt and eclogite with about 2% waterat 800-1300℃ and 1.0-3.5 GPa shows that the solidi of both rocks are significantly lower thanthose obtained from the previous experiments of the same type of rocks under dry conditions,and the former which is enriched in potassium has a lower melting point than the latter. It is con-sistent with the previous study. The melting temperature of eclogite increases with pressure,whereas potassic basalt has similar properties only at 1.5—2.5 GPa and>3.0 GPa, and at 2.5—3.0 GPa the melting temperature decreases with pressure. This can be explained as follows: (1)eclogite only has one hydrous mineral amphibole and the dehydous temperature is lower than thewet solidus of the rock. (2) Amphibole exists in potassic basalt at the pressures lower than 2.5GPa and phlogopite exists at pressures higher than 2.5 GPa, and the special compositions of bothminerals determine that amphibole has a dehydration temperature higher than or close to that ofthe wet solidus of the rocks, while phlogopite has a dehydration temperature lower than that ofthe wet solidus. On the other hand the features of the continuous solidus in the experiment ofhydrous eclogite were produced by the fact that the dehydration temperature of its amphibolelower than or close to the melting temperature of the hydrous conditions. So the melting tempera-ture lowers at higher pressures. Therefore, the composition of the rocks in the lithosphere and thetypes of hydrous minerals and their stable P-T conditions are the important factors controllingthe solidi of rocks. It can quite well explain the partial melting of rocks and the origin of the lowvelocity zone in the deep lithosphere.

Cr(Ⅲ) removal from simulated solution using hydrous magnesium oxide coated fly ash： Optimization by response surface methodology (RSM)

Hydrous magnesium oxide coated fly ash （MFA） has environmental remediation potential by providing a sub- strate for the adsorption of aqueous Cr（Ⅲ）. Aqueous Cr（Ⅲ） adsorption onto MFA was examined as a function of MFA dosage, pH and initial Cr（Ⅲ） concentration with the Box-Behnken approach used for experimental design and optimization using response surface methodology （RSM）. pH and dosage （dosage and concentration） have significant interactive effects on Cr（Ⅲ） adsorption efficiency. Analysis of variance shows that the response surface quadratic model is highly significant and can effectively predict the experimental outcomes. Cr（Ⅲ） removal effi- ciency of 98% was obtained using optimized conditions of MFA dosage, pH and initial Cr（Ⅲ） concentration of 1,5 7 g. L- 1, 4.11 and 126 mg. L- 1, respectively. Cr（Ⅲ） adsorption onto MFA is mainly attributed to the interaction between Or（Ⅲ） and the functional group --OH of the hydrous magnesium oxide, in all probability caused by chemisorptions. The results of this study can conduce to reveal the interactions between Cr（Ⅲ） pollutant and MFA characteristics, posing important implications for the cost-effective alternative adsorption technology in the treatment of heavy metal containing wastewater.

Raman and Infrared Spectroscopic Investigation of Some Hydrous LnTPPTS Complexes(Ln=La,Sm)

The Raman and IR spectra of LnTPPTS·10H 2O[Ln=La,Sm,TPPTS=P(m C 6H 4SO 3)3-3]complexes are reported.Based on the observed Raman and IR characteristic frequencies,a vibrational assignments has been made for these complexes.Coordination induces a lengthening of the S—O bonds and a shortening of the C—S bond.The C—S stretching frequencies should therefore increase while the position of the v(SO 3)should move to a lower wavenumber.Vibrational modes of metal oxygen polyhedronν(Ln—Ο)at 146,168,253 cm-1 are the structural charactrization for coordinate bond of LnTPPTS complexes.

Physicochemical Characterization of Surface Water of the Area of Gafsa

Water exploits an essential part in all the durable development, the exploitation of this natural resource, its management and its position, its mineralization, its underground course and the mode o fits resurgence. The area of Gafsa is known by its very important hydrous potential which is geographically in the zone of transition between central Tunisia and the Saharan platform, these two great fields are separated by the fault of Gafsa which plays an important part in the structuring of the basins of the area, the hydrous resources of Gafsa make subsoil water the principal source of supply water, in the absence of an important network of surface. The zones of studies present requirements out of water which do not cease growing with the progress of the industrial activities and the concentration of the agricultural activities： The objective of this work is to analyze the water of the various zones of the area of Gafsa and to treat it to make it possible most drinkable. The analyzes like measurement of pH, measurement of electric conductivity and measurement of dry residue were made in the laboratory of the chemical group of Mdhila in Tunisia and in laboratory of Ion exchanger Materials of Vitry in France, the processes of treatment as opposite osmosis are also programmed in this same laboratory. The results are very encouraging to start the study and the design of a station of potabilisation of water in the area of Gafsa.

Geoscience material structures prediction via CALYPSO methodology

Many properties of planets such as their interior structure and thermal evolution depend on the high-pressure properties of their constituent materials. This paper reviews how crystal structure prediction methodology can help shed light on the transformations materials undergo at the extreme conditions inside planets. The discussion focuses on three areas:(i) the propensity of iron to form compounds with volatile elements at planetary core conditions(important to understand the chemical makeup of Earth's inner core),(ii) the chemistry of mixtures of planetary ices(relevant for the mantle regions of giant icy planets), and(iii) examples of mantle minerals. In all cases the abilities and current limitations of crystal structure prediction are discussed across a range of example studies.

A Comparison Study on the δD Value of Polycyclic Aromatic Hydrocarbons in Hydrous Pyrolysate of Herbaceous Peat with Different Water Medium

To investigate the influence of diagenetic water media on the hydrogen isotopes of individual sedimentary aromatic compounds,a series of hydrous pyrolyses were conducted on herbaceous peat.Polycyclic aromatic hydrocarbons(PAHs)in hydrous pyrolysed samples and their hydrogen isotopic composition characteristics were studied.The aqueous medium demonstrated a significant influence on the hydrogen isotopic composition of the individual PAHs generated during pyrolysis.The results showed that the PAHs formed after pyrolysis in the presence of a saltwater medium with high δD value from a salt lake had a heavy hydrogen isotopic composition.The PAHs formed after pyrolysis in the presence of a fresh water medium with low δD value from a swamp had a light hydrogen isotopic composition.The difference in the average PAHδD value between the two hydrous experiments varied from -174‰ to -109‰,suggesting that the hydrogen isotopic composition of individual sedimentary PAHs can reflect the source of the diagenetic water medium.In addition,a comparative study found that the hydrogen isotopes of PAHs were superior to those of n-alkanes in the same sample for diagenetic water indications.The results indicated that the exchange of water-derived inorganic hydrogen and organic hydrogen was more intensive in freshwater experiments than in saltwater experiments.With an increase in the simulation temperature,the average δD value of PAHs generated in the hydrous simulation experiments showed an increasing trend,reflecting that the δD value of sedimentary PAHs formed with the participation of diagenetic water media was still closely related to the thermal maturity of organic matter.Comparative studies showed that theδD values of different types of organic compounds produced by hydrous pyrolysis of peat were in the order,PAHs>n-alkanes>methane.

Partial dehydration of brucite and its implications for water distribution in the subducting oceanic slab

Hydrous minerals within the subducting oceanic slab are important hosts for water.Clarification of the stability field of hydrous minerals helps to understand transport and distribution of water from the surface to the Earth’s interior.We investigated the stability of brucite,a prototype of hydrous minerals,by means of electrical conductivity measurements in both open and closed systems at 3 GPa and temperatures up to 1300 K.Dramatic increase of conductivity in association with characteristic impedance spectra suggests that partial dehydration of single-crystal brucite in the open system with a low water fugacity occurs at 950 K,which is about 300 K lower than those previously defined by phase equilibrium experiments in the closed system.By contrast,brucite completely dehydrates at 1300 K in the closed system,consistent with previous studies.Partial dehydration may generate a highly defective structure but does not lead to the breakdown of brucite to periclase and water immediately.Water activity plays a key role in the stability of hydrous minerals.Low water activity(a H_(2)O)caused by the high wetting behavior of the subducted oceanic slab at the transition zone depth may cause the partial dehydration of the dense hydrous magnesium silicates(DHMSs),which significantly reduces the temperature stability of DHMS(this mechanism has been confirmed by previous study on super hydrous phase B).As a result,the transition zone may serve as a‘dead zone’for DHMSs,and most water will be stored in wadsleyite and ringwoodite in the transition zone.

Anomalous elasticity of talc at high pressures:Implications for subduction systems

Talc is a layered hydrous silicate mineral that plays a vital role in transporting water into Earth’s interior and is crucial for explaining geophysical observations in subduction zone settings.In this study,we explored the structure,equation of state,and elasticity of both triclinic and monoclinic talc under high pressures up to 18 GPa using first principles simulations based on density functional theory corrected for dispersive forces.Our results indicate that principal components of the full elastic constant tensor C_(11) and C_(22),shear components C_(66),and several off-diagonal components show anomalous pressure dependence.This non-monotonic pressure dependence of elastic constant components is likely related to the structural changes and is often manifested in a polytypic transition from a low-pressure polytype talc-I to a high-pressure polytype talc-Ⅱ.The polytypic transition of talc occurs at pressures within its thermodynamic stability.However,the bulk and shear elastic moduli show no anomalous softening.Our study also shows that talc has low velocity,extremely high anisotropy,and anomalously high V_(P)/V_(S) ratio,thus making it a potential candidate mineral phase that could readily explain unusually high V_(P)/V_(S) ratio and large shear wave splitting delays as observed from seismological studies in many subduction systems.

First-principles calculations of structure and elasticity of hydrous fayalite under high pressure

The structures, elasticities, sound velocities, and electronic properties of anhydrous and hydrous fayalite （Fe2SiO4 and Fe1.75H0.5SiO4） under high pressure have been investigated by means of the density functional theory within the generalized gradient approximation （GGA） with the on-site Coulomb energy being taken into account （GGA＋U）. The optimized results show that H atoms prefer to substitute Fe atoms in the Fe1 site. Compared with the anhydrous fayalite Fe2SiO4, the mass density, elastic moduli, and sound velocities of Fe1.75H0.5SiO4 slightly decrease. According to our data, adding 2.3 wt% water into fayalite leads to reductions of compressional and shear wave velocities （VP and VS） by 3.4%-7.5% and 0.3%-3.4% at pressures from 0 GPa to 25 GPa, respectively, which are basically in agreement with the 2%-5% reductions of sound velocity obtained by the experimental measurement in the low velocity zones （LVZ）. Based on the electronic structure, the valence and conduction bands are slightly broader for hydrous fayalite. However, hydrous fayalite keeps the insulation characteristics under the pressures up to 30 GPa, which indicates that hydration has little effect on its electronic structure.

Investigation of Hydrous Pyrolysis on Type-Ⅱ Kerogen-bearing Source Rocks from Iran and its Application in Geochemical and Kinetic Analyses of Hydrocarbon Products

Hydrous pyrolysis(HP)practiced on type-Ⅱ kerogen-bearing oil shale samples from the Sargelu Formation in the Ghali-Kuh Area,western Iran,using a specially designed apparatus was performed at different temperatures(250-350℃),with hydrocarbon generation evaluated at each temperature.For comparison,the samples subjected to Rock-Eval pyrolysis before proceeding to HP resulted in T_(max)=418℃,HI=102,and TOC=4.33%,indicating immaturity and hence remarkable hydrocarbon(especially oil)generation potential,making them appropriate for HP.Moreover,the samples were deposited in a low-energy reductive marine environment,with maximum oil and gas generation(739 mg and 348 mg out of50 g of rock sample,respectively)observed at 330℃ and 350℃,respectively.The oil generated at 330℃ was subjected to gas chromatography(GC)and isotopic analyses to assess hydrocarbon quality and composition.The hydrocarbon generation data was devised to estimate kinetic indices of the Arrhenius equation and to investigate the gas-oil ratio(GOR)and overall conversion yield.Based on the producible hydrocarbon quantity and quality,the findings contribute to the economic assessment of oil shales across the study area.The developed kinetic model indicates the history of hydrocarbon generation and organic matter(OM)maturity.