Guangzhou Institute of Geochemistry
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Identification of intermediate-silicic cumulates in the Emeishan large igneous province, SW China
No full textGeochemical signatures of crystal accumulation in silicic igneous rocks are subtle and difficult to discern. However, the presence of silicic cumulates is required to explain the formation of silicic magmas by fractionation-dominated mechanisms. In large igneous provinces, such rock records are scarce if ever reported. In this study, we document a case example of identifying intermediate-silicic cumulates in the end-Guadalupian (similar to 260 Ma) Emeishan large igneous province, SW China. We demonstrate that syenitic rocks associated with the Panzhihua intrusion have textures and trace element geochemistry consistent with origins involving both crystal accumulation and melt extraction. Micro-X-ray fluorescence mapping shows that the rocks are either supported by a framework of interconnected, relatively large crystals of alkali feldspar, or by a fine- to medium-grained matrix. The former has relatively low SiO2, relatively high TiO2, Fe2O3, CaO, Na2O, Sr and Ba, and a characteristic positive Eu anomaly, whereas the latter has essentially the opposite features. All studied rocks have restricted initial Sr-Nd-Pb isotopic ratios that are similar to mafic rocks of the Panzhihua intrusion, requiring minimal contamination by the Precambrian basement of the Yangtze block. Because of delayed zircon saturation, Zr and Zr/Hf are less promising compared with Eu/Eu* and Ba in identifying cumulates in the studied rocks, a view that might hold in other intraplate magmatic systems. Our results, combined with available data, improve the current understanding of volcanic-plutonic connection concerning silicic magma types of the Emeishan large igneous province
Water solubility of olivine under redox-controlled deep upper mantle conditions: effects of pressure, temperature and coexisting fluids and implications
No full textWater as structural hydroxyl in olivine plays an important role in determining the water budget of the upper mantle and its numerous physicochemical properties. However, the solubility of water in olivine in the deep upper mantle (i.e., 300-410 km depth), which defines the maximum water content under given conditions, still needs to be known with high precision. We examined the water solubility by annealing experiments under conditions controlled by Fe-FeO buffer and peridotite assemblages at 10-13 GPa and 1100-1450 degrees C, using a starting olivine of representative chemistry and different fluid materials. The experimental conditions were broadly consistent with those prevailing in the deep upper mantle. The attainment of equilibrium water incorporation in the H-annealed olivine samples was ensured by H diffusion kinetics, water profile analyses and time-series studies. The annealed samples demonstrate infrared hydroxyl bands at 3650-3000 cm(-1), but the relative band patterns are different from those observed in the available H-annealing experiments at 1-7 GPa under otherwise comparable conditions (including starting materials). The obtained solubility of water increases with increasing both temperature and pressure over the run conditions, and differs apparently between the runs equilibrated by different fluids that are relevant to the deep upper mantle and water solubility studies. In general, the water solubility of olivine increases nonlinearly with increasing depth in the upper mantle, and can be described as: C-w = (290 +/- 78) x exp ((0.0043 +/- 0.0006) x depth (km))-(268 +/- 89) (H2O as coexisting fluid) and C-w = (149 +/- 72) x exp ((0.0046 +/- 0.0011) x depth (km))-(132 +/- 85) (CH4-H2O as coexisting fluid), where C-w is water solubility (ppm wt. H2O). The water solubility of olivine in the realistic upper mantle should be defined from the runs coexisting with CH4-H2O, and the highest value is only similar to 800 +/- 80 ppm wt. H2O, implying that the actual water contents of olivine in the upper mantle must be mostly (if not exclusively) lower. The inferred storage capacity of water in peridotite in the upper mantle reaches its maximum of 600 +/- 100 ppm wt. H2O (95% confidence level) at the bottom boundary of similar to 410 km depth, and a minimum of 350 +/- 50 ppm wt. H2O (95% confidence level) is expected at mid-depths of 190-230 km. During the upwelling of relatively water-rich materials from the source regions of enriched mid-ocean ridge basalts or ocean island basalts, hydrous melting would be much easier to trigger at the mid-depths of the upper mantle. The data further suggest that, to produce a pervasive hydrous melting at the similar to 410 km depth, the prevailing water content of the mantle transition zone should be greater than similar to 600 ppm wt. H2O
Organosulfur Compounds: A Non-Negligible Component Affecting the Light Absorption of Brown Carbon During North China Haze Events
No full textThe roles of organosulfur compounds (OSCs), an important component in organic matter, in brown carbon (BrC) aerosol absorption is often overlooked. Here, the molecular composition of OSCs and its associations with methanol-soluble BrC (MS-BrC) absorption during a haze event in North China were revealed using a Fourier transform ion cyclotron resonance mass spectrometry analysis. By combining aggregated boosted tree model and partial least squares regression estimation, our results suggested that OSCs were mainly composed of potential aromatic structures, and the MS-BrC absorption was closely related to OSCs. Specifically, OSCs contribute a notable 26% of the total potential BrC molecular number and an upper limit of 10.4% of total MS-BrC absorption. Furthermore, we found that OSCs were mainly influenced by coal combustion, and the potential desulfurization reactions showed associations with the variations of MS-BrC absorption. Since the residential coal combustion (an important primary source of OSs) was the major energy in North China, our research underscores the potential of aromatic OSCs as tracers for assessing the impact of fossil fuel combustion on BrC and highlights the important atmospheric influences of OSCs (e.g., light absorption and health), which need more works to uncover the origins, fates, and environmental effects of OSCs
Magnesium Isotope Fractionation During Basalt Weathering: An Index of Weathering Fluxes and CO<sub>2</sub> Consumption
No full textThe weathering of silicate rocks exerts a significant control on the weathering fluxes of metals and atmospheric CO2 consumption. In this study, we present new magnesium (Mg) isotope data from a basalt weathering profile in Hainan Island, South China, to investigate Mg isotope fractionation and calculate weathering fluxes and CO2 consumption. The Mg mobility (tau(Mg,Ti)) in saprolites decreases from -34.1% to -95.7%. The delta Mg-26 values in saprolites vary from -0.25 +/- 0.07 parts per thousand to 0.43 +/- 0.07 parts per thousand, higher than those of the parent rock (-0.25 +/- 0.07 parts per thousand). The significant Mg loss during the formation and decomposition of clay minerals influences Mg isotope fractionation, particularly with changes in kaolinite structure under different pH conditions, which prefer heavy Mg isotopes. By applying a mass balance model, we have developed a novel method to calculate weathering fluxes based on the weathering profile, yielding Mg elemental fluxes (Mg-Flux) of 2.45-5.85 mol/cm(2)/Myr, Mg isotopic fluxes (delta Mg-26(Flux)) of -0.44 to -0.04 parts per thousand/mol/cm(2)/Myr, and CO2 consumption of 2.3 x 10(12) mol/yr for the weathering outputs of basaltic rocks. This highlights the crucial role of basalt weathering in global carbon sequestration. Our findings improve the understanding of Mg cycling and isotope fractionation in epigenetic environments and facilitate the quantification of weathering fluxes and atmospheric CO2 consumption during basalt weathering
Unveiling the role of oxygen vacancies on different crystal planes of ceria in catalytic toluene oxidation: Evidence from molecular dynamics and in situ DRIFTS
No full textOxygen vacancy defect engineering is an efficient tactic in metal oxide catalysts for the oxidation of volatile organic compounds (VOCs). Herein, a series of CeO2 catalysts with different dominant crystal planes ((111), (220), (311), and (200)) were successfully synthesized via a facile one-step hydrothermal method. The catalytic oxidation performance for toluene followed the order: (111) > (220) > (311) > (200). Molecular dynamics simulation directly demonstrated that toluene molecule was more readily adsorbed on the (111) crystal planes of CeO2 at actual reaction temperature. The characterization results revealed the local microenvironment of oxygen vacancy could be tailored by different exposed crystal planes, in which (111) crystal planes could induce more coordinative unsaturated sites and then generate more Ce3+-V-O-Ce4+ sites. The in-situ DRIFT spectra further elucidated the catalytic toluene oxidation pathways over these CeO2 catalysts. For the NC-CeO2 (200) catalyst, the insufficient oxygen vacancies made it difficult for gaseous oxygen to backfill onto the surface of catalyst, which induced dehydrogenation of methyl group was the rate-determining step. While the toluene on the surface of NP-CeO2 (111) could be immediately transformed into benzyl alcohol. With the assistance of electrophilic oxygen species, the benzyl alcohol was further oxidized into benzaldehyde, benzoic acid, maleic anhydride, H2O, and CO2. This work provides valuable insights into the design of efficient CeO2 catalysts for VOCs degradation and advances the understanding of their catalytic mechanisms
<i>Using δD of methyl aromatics and oils to trace the reservoir charging characteristics of complex petroleum systems in Tarim Basin, northwestern China</i>
No full textAromatization occurs steadily during the petroleum evolution stage of light oil/condensate (LOC) formation, for which the composition and delta D of aromatics are of considerable geochemical significance. This paper presents a study on the composition and delta D of monomethyl aromatic compounds (toluene, methylnaphthalene, methylphenanthrene, and methyldibenzothiophene) and related hydrocarbon compounds in LOCs from the Tazhong uplift area of the Tarim Basin in China. Thermal maturity, the source rock of the LOCs, and the effect of gas washing on the oils are discussed. The calculated reflectance of the oils using methyldibenzothiophene and dimethylnaphthalene parameters is approximately 1.15%-1.5%. The thermal maturity of the oils in the Tazhong I fault-slope zone is slightly higher than that of the oils in the Tazhong 10 structural belt due to the more intense gas washing of the oils in the former. The varying degrees of gas washing also caused enrichment of low-carbon-number aromatic hydrocarbons and their H-2 isotopes in the oils of the Tazhong I fault-slope zone relative to those of the Tazhong 10 structural belt. In addition to the contributions from lower Cambrian and Middle-Upper Ordovician source rocks, these crude oils may have received contributions from upper Cambrian Furongian source rocks deposited within locally shielded environments. Crude oils such as TZ62(Silurian) and ZG432(Ordovician) contain heavy delta C-13 but light delta D isotopic compositions and may represent end member oils derived from Furongian source rocks
Valorization of alcohol industry residues into solid, gaseous and liquid biofuels: A comprehensive review
No full textAlcohol industry residues (AIRs) are typical organic solid wastes from a major light industry while belong to renewable biomass resource, and their annual accumulation amount is significant and rapidly increasing worldwide. The clean and efficient utilization of AIRs is urgently needed, driving the development of valorization technologies with the waste-to-energy strategy which is considered as the most practical and sustainable method. In recent decades, significant attention has focused on unlocking the energy potential of AIRs. However, current technologies face significant challenges in producing desirable biofuels from AIRs in an eco-friendly, carbon- neutral, and economically efficient manner, credit to the restriction of their unfavorable properties such as high initial moisture, nitrogen, and oxygen contents. In this review, the energy valorization of AIRs using thermo- and bio-chemical conversion technologies is comprehensively reviewed and compared. The preparation methods, properties, and thermal use of various biofuels are systematically summarized. Low or medium-temperature hydrothermal technology demonstrates significant advantages in converting AIRs into desired biofuels, either as a pretreatment or preparation method. This strategy can produce modified solid biofuel by upgrading and denitrogenating capabilities, and improve biogas and bioethanol yields through boosted hydrolysis reactions. Combining hydrothermal with other conversion methods would be a promising research avenue for valorizing AIRs into energy, enabling the poly-generation of targeted biofuels by selectively regulating the evolution of specific elements. This review can offer an overview and insights into effectively managing and utilizing AIRs for researchers in the field
The partitioning of chalcophile and siderophile elements (CSEs) between sulfide liquid and carbonated melt
No full textCarbonated melts play a significant role in mobilizing lithophile and volatile elements in the Earth's mantle and mantle metasomatism. However, there has been limited investigation into their potential for mobilizing chalcophile and siderophile elements (CSEs). In this study, we experimentally determine the sulfide liquid- -carbonated melt partition coefficients of CSEs ( D Sul / C melt CSE) for a range of elements, including Co, Ni, Cu, Zn, Se, Mo, Ag, Cd, In, Sn, Re, and Pb, at 1300-1600 degrees C, 1.0-3.0 GPa, and oxygen fugacity (fO2) close to the graphiteCO2 fluid buffer. Furthermore, the D Sul / C melt values for lithophile elements Cr, Mn, Rb, Sr, Y, Zr, Nb, Cs, Ba, Hf, and Ta ( D Sul / C melt LithoE ) are also determined. The obtained D Sul / C melt values are 34-1230 for Co, 380-75200 for Ni,CSE 200-14900 for Cu and Ag, 0.5-28 for Zn and Mo, 42-98 for Se, 24-640 for Cd, 5-52 for In and Sn, 650-15200 for Re, and 22-2470 for Pb. The obtained D Sul / C melt LithoE values are below 1-10. The variations of D Sul / C melt and D Sul / C melt CSE LithoE are primarily influenced by the FeOtot content in the carbonated melts. A partitioning model was developed to parameterize D Sul / C melt and D Sul / C melt LithoE as a multi-function of pressure, temperature, composition of the carbonCSE ated melt (mainly the FeOtot content), and composition of the sulfide liquid. Our parameterization can explain the observed large variations of D Sul / C melt and D Sul / C melt CSE LithoE for most of the trace elements studied. Using our D Sul / C melt parameterization, we model the CSE and U-Th contents of low-degree partial melts of carbonated CSE mantle peridotite and slab eclogite with sulfur concentrations ranging from 50 to 500 mu g/g. The modeling results can generally explain the trace element patterns observed in natural kimberlites and carbonatites; however, the peridotite- or slab-derived carbonated melts have a low capability in mobilizing CSEs, which can extract less than 3 % of Cu, Ni, Co, Re, and Os, 3-30 % of Mo, Pb, and Se, but up to 30-50 % U and Th from the source lithology. Consequently, the influence of carbonatite metasomatism on the Cu, Ni, Co, Re, and Os systematics of the Earth's mantle is minimal, although local enrichments of CSEs may occur when sulfides precipitate from carbonated melts. Because of the elevated concentrations of U and Th and the corresponding U/Pb and Th/Pb ratios in the carbonated melts, the mantle lithology that has undergone metasomatism by these melts can become a geochemical reservoir with high 208 Pb/ 206 Pb ratios. However, the effect of carbonatite metasomatism on Re-Os isotopic systems of the mantle is minimal due to the low Re concentrations in the carbonated melts. Accordingly, the radiogenic Pb-Os isotopic signatures of HIMU ocean island basalts cannot be explained solely by carbonatite metasomatism in the mantle
The partitioning of chalcophile and siderophile elements (CSEs) between sulfide liquid and carbonated melt
No full textCarbonated melts play a significant role in mobilizing lithophile and volatile elements in the Earth's mantle and mantle metasomatism. However, there has been limited investigation into their potential for mobilizing chalcophile and siderophile elements (CSEs). In this study, we experimentally determine the sulfide liquid- -carbonated melt partition coefficients of CSEs ( D Sul / C melt CSE) for a range of elements, including Co, Ni, Cu, Zn, Se, Mo, Ag, Cd, In, Sn, Re, and Pb, at 1300-1600 degrees C, 1.0-3.0 GPa, and oxygen fugacity (fO2) close to the graphiteCO2 fluid buffer. Furthermore, the D Sul / C melt values for lithophile elements Cr, Mn, Rb, Sr, Y, Zr, Nb, Cs, Ba, Hf, and Ta ( D Sul / C melt LithoE ) are also determined. The obtained D Sul / C melt values are 34-1230 for Co, 380-75200 for Ni,CSE 200-14900 for Cu and Ag, 0.5-28 for Zn and Mo, 42-98 for Se, 24-640 for Cd, 5-52 for In and Sn, 650-15200 for Re, and 22-2470 for Pb. The obtained D Sul / C melt LithoE values are below 1-10. The variations of D Sul / C melt and D Sul / C melt CSE LithoE are primarily influenced by the FeOtot content in the carbonated melts. A partitioning model was developed to parameterize D Sul / C melt and D Sul / C melt LithoE as a multi-function of pressure, temperature, composition of the carbonCSE ated melt (mainly the FeOtot content), and composition of the sulfide liquid. Our parameterization can explain the observed large variations of D Sul / C melt and D Sul / C melt CSE LithoE for most of the trace elements studied. Using our D Sul / C melt parameterization, we model the CSE and U-Th contents of low-degree partial melts of carbonated CSE mantle peridotite and slab eclogite with sulfur concentrations ranging from 50 to 500 mu g/g. The modeling results can generally explain the trace element patterns observed in natural kimberlites and carbonatites; however, the peridotite- or slab-derived carbonated melts have a low capability in mobilizing CSEs, which can extract less than 3 % of Cu, Ni, Co, Re, and Os, 3-30 % of Mo, Pb, and Se, but up to 30-50 % U and Th from the source lithology. Consequently, the influence of carbonatite metasomatism on the Cu, Ni, Co, Re, and Os systematics of the Earth's mantle is minimal, although local enrichments of CSEs may occur when sulfides precipitate from carbonated melts. Because of the elevated concentrations of U and Th and the corresponding U/Pb and Th/Pb ratios in the carbonated melts, the mantle lithology that has undergone metasomatism by these melts can become a geochemical reservoir with high 208 Pb/ 206 Pb ratios. However, the effect of carbonatite metasomatism on Re-Os isotopic systems of the mantle is minimal due to the low Re concentrations in the carbonated melts. Accordingly, the radiogenic Pb-Os isotopic signatures of HIMU ocean island basalts cannot be explained solely by carbonatite metasomatism in the mantle
Microbial recruitment and microbial ecological roles in soil nutrient cycling of Populus cathayana males and females
No full textSoil nitrogen (N) availability influences plant production and soil nutrient cycling. However, how it influences sex-specific microbial community composition and rhizosphere nutrient cycling in dioecious plant species is poorly understood. We examined the rhizospheric bacterial and fungal community assemble and their influences on soil nutrient cycling under different N backgrounds in 30-year-old experimental stands and a soil microbial reshaping-controlled experiment. In comparison to male trees, female trees increased fungal community diversity, and the relative abundance of taxa related to nutrient availability; elevated phosphorus (P) mobilization by increasing acidic phosphatase activity and carboxylic acid release; and decreased the counts of denitrification nirS, nirK, and nosZ genes at high N supply. Males increased the nifH gene counts related to microbial N fixation at high N supply. Low N supply increased N fixation nifH gene counts in the rhizosphere of females. Males decreased bacterial and fungal diversity, increased enzymatic activities related to organic N and P mineralization, and elevated soil nitrate-nitrogen levels at low N supply. Our results indicate that sex-specific responses to N availability are associated with rhizospheric bacterial and fungal community composition and diversity and their effects on rhizospheric nutrient cycling, which may explain sex-specific resource utilization and niche differentiation