Equilibrium Si isotope fractionation factors among orthosilicic acid(i.e.,H4 Si O4(aq)), quartz and the adsorption complexes of H4 Si O4(aq)on Fe(III)-oxyhydroxide surface were calculated using the full-electron wave-...Equilibrium Si isotope fractionation factors among orthosilicic acid(i.e.,H4 Si O4(aq)), quartz and the adsorption complexes of H4 Si O4(aq)on Fe(III)-oxyhydroxide surface were calculated using the full-electron wave-function quantum chemistry methods [i.e., B3LYP/6-311G(2df,p)]with a new cluster-model-based treatment. Solvation effects were carefully included in our calculations via water-droplet method combined with implicit solvent models(e.g., PCM).The results revealed that, if it is under equilibrium conditions,heavy Si isotopes would be significantly enriched in quartz in comparison to H4 Si O4(aq). However, most of the field observations suggested that quartz would have identical or even depleted d30 Si values compared to that of H4 Si O4(aq). To explain this discrepancy between the equilibrium calculation results and the field observations, the kinetic isotope effect(KIE) associated with the formation of amorphous silica,which usually is the precursor of crystalline quartz, was investigated using quantum chemistry methods. The KIE results showed that amorphous silica would be significantly enriched in light Si isotopes during its formation. Our equilibrium fractionation results, however, matched a special type of quartz(i.e., Herkimer ‘‘diamond'') very well, due to its nearly equilibrated precipitation condition. Opposite to the case of precipitated quartz, a large equilibrium Si isotope fractionation(i.e.,-3.0 %) was found between the absorbed bidentate Si surface complexes(i.e.,2C [ Fe2O2Si(OH)2) and H4 Si O4(aq). This calculated equilibrium Si isotope fractionation factor largely differed from a previous experimental result(ca.-1.08 %). We found that the formation of transient or temporary surface complexes [e.g.,1V [ Fe2OSi(OH)3] may have accounted for the smaller net fractionation observed.With the equilibrium and kinetic Si isotope fractionation factors provided here, the distributions and changes of Si isotope compositions in the Earth's surface systems can be better understood.展开更多
Oxygen isotope fractionation was experimentally studied in the quartz-wolframite-water systemf rom 200 to 420℃.The starting wolframite was synthexized in aqueous solutions of Na2WOR·2H2O+FeCl2·4H2O or MnCl2...Oxygen isotope fractionation was experimentally studied in the quartz-wolframite-water systemf rom 200 to 420℃.The starting wolframite was synthexized in aqueous solutions of Na2WOR·2H2O+FeCl2·4H2O or MnCl2·4H2O.The starting solutions range in salinity from 0 to 10 equivalent wt.% NaCl.Experiments were conducted in a gold-lined stainless steel autoclave,with filling degrees of about 50%.The results showed no significant difference in dquilibrium isotope fractionation between water and wolframite,ferberite and huebnerite at the same temperature(310℃）.The equilibrium oxygen isotope fractionation factors of wolframite and water tend to be equal with increasing temperature above 370℃.but to increase significantly with decreasing temperature below 370℃.展开更多
Production of modified liquid glass and quartz materials from kaolinite clay of Alekseev deposit of Kazakhstan was studied. The sodium liquid glass processed by kaolinite clay, with chemical composition (g/dm3): SiO2-...Production of modified liquid glass and quartz materials from kaolinite clay of Alekseev deposit of Kazakhstan was studied. The sodium liquid glass processed by kaolinite clay, with chemical composition (g/dm3): SiO2-350;Na2O-155;Al2O3-2.1;Fe2O3- 0.3, silicate module-2.33 and density-1.49 g/cm3 has been used. The sodium liquid glass complies with the Russian Interstate standard 13078-81 for sodium liquid glass.10 samples of modified liquid glass were synthesized by introducing modifiers in an amount of 4% by weight of the solution into the liquid glass. Hard quartz material produced by using synthesized modified liquid glass was obtained. It has been established that the obtained modified liquid glass from kaolinite clay can improve the strength of the quartz material for 1.6 - 3.12 times higher than the initial liquid glass. Using liquid glass modifier to the inorganic sodium nitrate (NaNO3) increases the strength 3.12 times.展开更多
基金funding support from the 973 Program (2014CB440904)the Chinese NSF projects (41490635, 41173023, 41225012)
文摘Equilibrium Si isotope fractionation factors among orthosilicic acid(i.e.,H4 Si O4(aq)), quartz and the adsorption complexes of H4 Si O4(aq)on Fe(III)-oxyhydroxide surface were calculated using the full-electron wave-function quantum chemistry methods [i.e., B3LYP/6-311G(2df,p)]with a new cluster-model-based treatment. Solvation effects were carefully included in our calculations via water-droplet method combined with implicit solvent models(e.g., PCM).The results revealed that, if it is under equilibrium conditions,heavy Si isotopes would be significantly enriched in quartz in comparison to H4 Si O4(aq). However, most of the field observations suggested that quartz would have identical or even depleted d30 Si values compared to that of H4 Si O4(aq). To explain this discrepancy between the equilibrium calculation results and the field observations, the kinetic isotope effect(KIE) associated with the formation of amorphous silica,which usually is the precursor of crystalline quartz, was investigated using quantum chemistry methods. The KIE results showed that amorphous silica would be significantly enriched in light Si isotopes during its formation. Our equilibrium fractionation results, however, matched a special type of quartz(i.e., Herkimer ‘‘diamond'') very well, due to its nearly equilibrated precipitation condition. Opposite to the case of precipitated quartz, a large equilibrium Si isotope fractionation(i.e.,-3.0 %) was found between the absorbed bidentate Si surface complexes(i.e.,2C [ Fe2O2Si(OH)2) and H4 Si O4(aq). This calculated equilibrium Si isotope fractionation factor largely differed from a previous experimental result(ca.-1.08 %). We found that the formation of transient or temporary surface complexes [e.g.,1V [ Fe2OSi(OH)3] may have accounted for the smaller net fractionation observed.With the equilibrium and kinetic Si isotope fractionation factors provided here, the distributions and changes of Si isotope compositions in the Earth's surface systems can be better understood.
基金This projects was financially supported by the National Natural Science Foundation of China.
文摘Oxygen isotope fractionation was experimentally studied in the quartz-wolframite-water systemf rom 200 to 420℃.The starting wolframite was synthexized in aqueous solutions of Na2WOR·2H2O+FeCl2·4H2O or MnCl2·4H2O.The starting solutions range in salinity from 0 to 10 equivalent wt.% NaCl.Experiments were conducted in a gold-lined stainless steel autoclave,with filling degrees of about 50%.The results showed no significant difference in dquilibrium isotope fractionation between water and wolframite,ferberite and huebnerite at the same temperature(310℃）.The equilibrium oxygen isotope fractionation factors of wolframite and water tend to be equal with increasing temperature above 370℃.but to increase significantly with decreasing temperature below 370℃.
文摘Production of modified liquid glass and quartz materials from kaolinite clay of Alekseev deposit of Kazakhstan was studied. The sodium liquid glass processed by kaolinite clay, with chemical composition (g/dm3): SiO2-350;Na2O-155;Al2O3-2.1;Fe2O3- 0.3, silicate module-2.33 and density-1.49 g/cm3 has been used. The sodium liquid glass complies with the Russian Interstate standard 13078-81 for sodium liquid glass.10 samples of modified liquid glass were synthesized by introducing modifiers in an amount of 4% by weight of the solution into the liquid glass. Hard quartz material produced by using synthesized modified liquid glass was obtained. It has been established that the obtained modified liquid glass from kaolinite clay can improve the strength of the quartz material for 1.6 - 3.12 times higher than the initial liquid glass. Using liquid glass modifier to the inorganic sodium nitrate (NaNO3) increases the strength 3.12 times.
