Carbon isotopic compositions of pore and matrix carbonates in carbonate nodules, and origin of carbonate formation

Carbon isotopes of pedogenic carbonate are often used to study paleoenvironments, but the existence of detrital carbonate changes the carbon isotopic composition. To develop an experimental method to determine existence of detrital carbonate in carbonate nodules, and to avoid it during isotope analysis, 23 pedogenic carbonate nodules in Miocene loess from the Loess Plateau of China were studied through micromorphology and carbon isotope analysis. The difference in carbon isotopic composition between matrix carbonate (B) and pore carbonate (A) (δ¹³C_(B-A)) ranges from 0.27‰ to 0.44‰ in nodules containing detrital carbonate and –0.16‰ to 0.13‰ in nodules where detrital carbonate is absent. The latter is within measurement error, but the former is beyond it. Here we propose an isotopic approach to determine if nodules contain detrital carbonate: if δ¹³C_(B-A) is within the measurement error, the nodules do not contain detrital carbonate, and vice versa. We suggest that it is better to analyze pore carbonate instead of matrix carbonate when using carbon isotope of carbonate nodules to reconstruct paleoenvironments.     

Stable isotopes of modern herbivore tooth enamel in the Tibetan Plateau: Implications for paleoelevation reconstructions

Fossil tooth enamel from herbivores is considered one of the best proxies for paleoclimate and paleoelevation reconstructions, due to its low susceptibility to diagenetic alteration. A synthesis of oxygen and carbon isotope analyses of modern tooth enamel from herbivores such as Tibetan yaks, asses and antelopes is assessed. The average δ 13C(PDB) value of herbivore tooth enamel in the Lhasa and south Qiangtang terrains is-11.3‰± 1.1‰, whereas in the north Qiangtang and Hoh Xil terrains value is-10.2‰± 1.4‰...     

δ13C difference between plants and soil organic matter along the eastern slope of Mount Gongga

Carbon isotope ratios (δ¹³C) of plants, litter and soil organic matter (0–5 cm, 5–10 cm and 10–20 cm) on the eastern slope of Mount Gongga were measured. The results show that δ¹³C values of plants, litter and soil organic matter all decrease first and then increase with altitude, i.e δ¹³C values gradually decrease from 1200 to 2100 m a.s.l., and increase from 2100 to 4500 m a.s.l. The δ¹³C altitudinal variations are related to the distribution of C₃ and C₄ plants on the eastern slope of Mount Gongga, because C₄ plants are observed to grow only below 2100 m, while C3 plants occur at all altitudes. There are significantly positive correla-tions among δ¹³C of vegetation, δ¹³C of litter and δ¹³C of soil organic matter, and litter, 0–5 cm, 5–10 cm and 10–20 cm soil or-ganic matter are 0.56‰, 2.87‰, 3.04‰ and 3.49‰ greater in δ¹³C than vegetation, respectively. Considering the influences of rising concentration of atmospheric CO₂ and decreasing δ¹³C of atmospheric CO₂ since the industry revolution on δ¹³C of plants, 1.57‰ is proposed to be the smallest correction value for reconstruction of paleovegetation using δ¹³C of soil organic matter.     

Distribution of <Emphasis Type="Italic">δ</Emphasis><Superscript>18</Superscript>O in surface snow along a transect from Zhongshan Station to Dome A,East Antarctica

Surface snow samples were collected during the 14th (1997/1998) and 24th (2007/2008) Chinese National Antarctica Research Expeditions along a transect from Zhongshan Station to Dome A. The stable oxygen isotope ratios of these samples were measured to investigate their relationships with temperature and geographical parameters (latitude, longitude, altitude and distance to the coast). The results reveal a strong positive correlation (R=0.945) between δ¹⁸O and mean annual temperature, with a gradient of 0.84‰°C ^–1, which is a little higher than that in Terre Adelie Land. Regression analyses also show that the δ¹⁸O of surface snow is strongly correlated with distance to the coast (R=0.942), latitude (R=0.942), and altitude (R=0.941). But no significant correlation was found between δ¹⁸O and longitude in study area. Altitude should be the most important factor influencing the δ¹⁸O distribution because of distinctive topography. The δ¹⁸O-altitude and T-altitude gradients along this transect are determined to be –1.1‰/100 m and 1.31°C/100 m, respectively.     

Carbon and nitrogen stable isotope analyses of mammal bone fossils from the Zhongba site in the Three Gorges Reservoir region of the Yangtze River,China

Based on AMS ¹⁴C dating data, carbon and nitrogen isotope analyses were conducted on mammal bone collagen of deer, cattle and pigs from the Zhongba site in the Three Gorges Reservoir region of the Yangtze River. These analyses were conducted to reconstruct palaeodiets of mammals, palaeoecology, palaeoenviroment and previous human activities in the study area. Results show that the collagen loss of bone did not change the in vivo isotopic composition of carbon and nitrogen stable isotopes, and most of the bone fossils were well preserved. The bone collagen of samples from deer had a mean δ¹³C of -23.1‰ and a mean δ¹⁵N of 4.7‰, suggesting that deer subsisted in a closed habitat and fed on branches and leaves. The bone collagen of cattle had a mean δ¹³C of –19.6‰ and a mean δ¹⁵N of 5.2‰, which indicates that cattle subsisted in an open habitat and fed on grasses and stems. The δ¹³C values show that both deer and cattle fed on C₃ plants and lived in the same ecosystem, but the t-test results show that deer δ¹³C and δ¹⁵N values were both more negative than those of cattle, indicating that they inhabited different niches. The δ¹³C and δ¹⁵N values of cattle partially overlapped those of deer, suggesting some competition in diets between them. The t-tests show that the δ¹³C and δ¹⁵N values of pigs were more positive than those of cattle and deer, which signifies that pigs occupied a higher trophic level compared to cattle and deer. The wide range of pig δ¹³C values demonstrates that pig trading had been taking place from early Neolithic Age to late Bronze Age. There were no significant differences in deer δ¹³C and δ¹⁵N values among different archaeological periods, making it clear that climatic, ecological and environmental conditions were kept relatively stable from 2200 to 4200 a BP. This stability may have been responsible for the extensive and complete cultural layers at the Zhongba site. The minimum number of samples required to estimate the mean δ¹³C values of deer, pigs and cattle are 8, 73 and 16, respectively, and for mean δ¹⁵N values of deer, pigs and cattle, the minimum numbers are 4, 5 and 6, respectively.     

High-resolution carbon isotope record for the Paleocene-Eocene thermal maximum from the Nanyang Basin,Central China

The Paleocene-Eocene thermal maximum (PETM) was a transient episode of global warming, associated with massive atmospheric greenhouse gas input that occurred at the Paleocene/Eocene boundary. Biostratigraphic and isotope stratigraphic studies indicate that the PETM event is well documented in the marl deposits of the Yuhuangding section in the Nanyang Basin, Central China, with a carbon isotope negative excursion of ~6.1‰ within 19-m-thick marl deposits. This is the highest resolution record of the PETM so far found in the world. The PETM event was triggered within 2-cm-thick marl sediments, with a decrease of δ¹³C (stable carbon isotope ratio) from –3.2‰ to –5.2‰, suggesting a massive methane hydrate release for a transient period that was possibly caused by a catastrophic event. A comparison between marine and terrestrial records indicates a “Three-Phase Model” for the PETM event. Initially there is a rapid negative excursion in the δ¹³C record, followed by a slowly decreasing trend, and then a gradual positive recovery, corresponding respectively to a rapid dissociation of oceanic methane hydrate, followed by a slow release of methane and then the consumption of the released methane.     

Indicators of δ13C and δ18O of gas hydrate-associated sediments

The analyses of δ13C and δ18O of gas hydrate-associated sediments from two cores on Hydrate Ridge in Cascadia convergent margin offshore Oregon, eastern North Pacific show the values of d 13C from -29.81‰ to -48.28‰ (PDB) and d 18O from 2.56‰ to 4.28‰ (PDB), which could be plotted into a group called typical carbonate minerals influenced by the methane in cold venting. Moreover, the values of d 13C and d 18O show a consistent trend in both cores from top to bottom with increasing of d 13C and decreasing of d 18O. This trend could be explained as an effect caused by the anaerobic oxidation of methane (AOM) in depth and the oxygen fraction during the formation of gas hydrate in depth together. These characteristics of d 13C and d 18O indicate that the gas hydrate-associated sediments are significantly different from the normal marine carbonates, and they are deeply influenced by the formation and evolution of gas hydrate. So, the distinct characteristics of d 13C and d 18O of gas hydrate-associated sediments could be undoubtedly believed as one of parameters to determine the presence of gas hydrates in other unknown marine sediment cores.     

<Superscript>40</Superscript>Ar/<Superscript>39</Superscript>Ar isochron ages of lawsonite blueschists from Jiuquan in the northern Qilian Mountain,NW China,and their tectonic implications

Using laser ⁴⁰Ar/³⁹Ar dating method, we have gotten the metamorphic ages of lawsonite blueschist and epidote blueschist from Jiuquan, northern Qilian Mountain, NW China. The high quality laser ⁴⁰Ar/³⁹Ar dating of glaucophane from lawsonite blueschist gives an isochron age of 413±5 Ma. The isochron age obtained from phengite in epidote blueschist is 415±7 Ma. These data, combining with peak metamorphic P-T conditions and regional geological setting, allow us to infer that the lower limit of the ages of the prograde subduction metamorphism from lawsonite blueschist facies to epidote blueschist facies occurred at ca. 413–415 Ma, which also suggests that the formation of lawsonite blueschist in the northern Qilian Mountain maybe resulted from the corner flow in the cold subduction zone. This study shows that the final closing time of the northern Qilian remnant oceanic basin is about 413–415 Ma, which also represents the convergent age between the North China Craton and the Qaidam block.     

Mo isotopes in the Lower Cambrian formation of southern China and its implications on paleo-ocean environment

Over the past decade, as one of nontraditional stable isotopes, Mo isotope has developed rapidly and now become an important geochemical proxy to trace paleo-oceanic and atmospheric evolution through geological history. In this paper, Early Cambrian formations in southern China are investigated. The results indicate that δ 97/95Mo values of Early Cambrian seawater may have been larger than 1.4‰, values that are close to those of the modern ocean. It was also found that the variations in Mo isotope composition in samples from two sections （Huangjiawan and Gezhongwu in Guizhou） were closely related to changes in redox conditions during sedimentary processes. Combining our results with existing data, a preliminary model for the evolution of seawater Mo isotope composition through geological history was provided. It indicated that Mo isotopic variations were generally consistent with the evolution of atmospheric oxygen.     

新型中温离子导体复合膜:Sn_(0.94)Sc_(0.06)P_2O_7和聚四氟乙烯(PTFE)

采用固相法合成中温离子导体Sn0.94Sc0.06P2O7和聚四氟乙烯(PTFE)的复合膜,并进行XRD,SEM及DSCTGA测试表征.用电化学工作站研究了复合膜在75~225℃下的导电特性.SEM分析结果表明复合膜具有良好的微观结构,XRD分析结果表明复合膜已形成了单相的SnP2O7立方相结构.气体气氛对复合膜电导率有显著的影响,σ(dry air)#σ(wet air)#σ(wet H2).该复合膜在湿润H2气氛中150℃下,电导率达到最大值6.5×10-4 S·cm-1.     

The impact of HS radicals on the measured rate constant of H<Subscript>2</Subscript>S with OH radicals

The rate constant for the reaction of OH radicals and hydrogen sulfide (H₂S) was studied in different bath gases (including N₂, air, O₂ and He) by using relative technique at 298 K. The small difference of the measured rate constants between N₂ and those with the presence of O₂ suggested possible influence of HS self reaction. Further experiments with NO_x presence for scavenging HS demonstrated this assumption. The rate constant of (5.48±0.12) ×10^–12 cm³ molecule^–1 s^–1 obtained with 4.09 ×10^–4 mol m₃ NO presence may be accurate for estimating the atmospheric lifetime of H2S. The results provided circumstantial evidence that the rapid reaction of HS with N₂O is suspected.     

算子乘积的本质谱

设A为Hilbert空间H上的有界线性算子, 若任给B∈B(H),有 σ_e(AB)=σ_e(BA),则称 A为一个一致Fredholm算子(简写为CF算子)或者称算子A具有CF性质, 其中σ_e(·)表示本质谱。 给出了算子具有CF性质的充要条件, 并且考虑了算子的紧摄动的CF性质;研究了算子矩阵的CF性质。     

Geochronology of the Hannan intrusive complex to adjoin the Qinling orogen and its rapid cooling reason

The geochronological works for the Hannan intrusive complex, cosisting of the gabbro-quartz dio-rite-plagiogranite bodies, in the north border of the Yangtze craton block, adjoining the Qinling orogen, are reported, because its age and genesis are of great importance to research of the tectonic evalutional history for the Qinling orogen and of the rifted processes for the Late Proterozoic supercontinent Rodinia. A good isochron of t=(837±26) Ma (2σ), corresponding to INd=0.51165±2(2σ), εNd(t)=+1.9, MSWD1.02, was difined by the Nd isotopic analytical results for the 21 whole-rock samples from the varied lithological complex bodies, but for the Rb-Sr isotopic aralytical data there is no isochron. The 40Ar/39Ar plateau age of the biotite, sorted from plagiogranites, is (796±20) Ma(2σ), and yet for the Rb-Sr isotopic data of the plagiogranite whole-rock samples (WR) and the sorted biotite (Bio), plagioclase (Plag) and apatite (Apt) mineral samples from the plagiogranitewhole-rock samples, an isochron of t=(824.86±3.8) Ma (2σ) with ISr=0.70393±14(2σ), MSWD2.44 is given. The U-Pb isotopic results for the single zircon, sorted from pla-giogranite samples, yielded an upper and a lower intercept ages of -876 Ma and -273 Ma. The Nd isotope data of complex indicate that it is probably the products of crystallization differentiation from the magma with 3333Nd>0 when the rapid uplift in 837-800 Ma took place in the northern border of the Yangtze craton block.     

Geochemical characteristics and formation process of natural gas in Kela 2 gas field

 On the basis of a large amount of natural gascomponents and the carbon isotope as well as some otheranalysis data in Kela 2 gas field, the geochemical character-istics, source, origin, and formation process of natural gashave been discussed. The components of gas in the field tendto be "dry", and the drying coefficient is close to 1.0. Thecarbon isotope tends to be heavier, for instance, the averageof δ¹³C₁ is -27.36‰ and that ofδ¹³C₂ is -18.5‰. Compre-hensive analysis shows that humic natural gas in the Kuqapetroleum system comes mainly from Triassic and Jurassicsource rocks, and the contribution of Jurassic source rocks tothe pool maybe is more than that of Triassic rocks. The maincause that the gas tends to be dry and bears heavier isotopecomposition lies in the fact that Kela 2 natural gas is the ac-cumulation of late production of humic source rocks, and itis affected by the abnormal high pressure as well. Consider-ing the hydrocarbon generating and structural history, wecan regard the gas pool formation processes as twice fillingand twice adjusting (destroying), that is, the filling anddestroying process in the early Himalayan movement and thefilling and adjusting in the late Himalayan movement.     

First mass measurement of short-lived nuclides at HIRFL-CSR

Recent commissioning of the HIRFL-CSR has demonstrated its ability to perform direct mass measurement for short-lived nuclides. Projectile fragments produced by the 78Kr ions at 481.88 MeV/u were separated with the new radioactive beam line in Lanzhou （RIBLL2）, and injected into and stored in the experimental storage ring （CSRe）. By operating the CSRe as an isochronous mass spectrometry, a typical mass resolution around 2.0×10？5 has been achieved. The masses for 63Ge, 65As and 67Se were measured for the first time. The measured masses are compared with theoretical predictions and the location of the proton drip-line for As isotopes is discussed. The implication of the 65As mass in the astrophysical rapid proton capture process has also been addressed.     

Features of major greenhouse gases in loess, Shanxi Province, China

According to the investigations of five loess sections in Shanxi Province, China, it was found that the concentrations of the major greenhouse gases CO₂, CH₄ and N₂O in loess-paleosol sequences are generally high, even sometimes may be several times or scores of times higher than their atmospheric concentrations respectively. Although the CO₂ concentration in the same loess section shows poor regularity among different layers, it increases slowly from north to south in space. The CH₄ concentration in the layers under Malan Loess is much higher than that in the atmosphere, although it is not high in Malan Loess. Most of the δ¹³C values of CO₂ in loess are -11.14‰—15.48‰ (relative to PDB standard). Analysis of carbon isotopic compositions of CO₂ indicates that the main source of CO₂ in loess section is decomposition of ‘stable’ organic matters by microbes. The δ¹³C_g of CO₂ is a little heavier than organic source for exchanging carbon isotope with carbonate in loess. The abundant carbonate in loess not only makes the loess a huge carbon reservior but also adjusts     

Relationship between climatic conditions and the relative abundance of modern C3 and C4 plants in three regions around the North Pacific

Using −24‰ and −14‰ as the endpoints of stable carbon isotopic composition of total organic carbon (δ¹³C_TOC) of surface soil under pure C₃ and C₄ vegetation, and surface soil δ¹³C_TOC data from eastern China, Australia and the Great Plains of North Amer- ica, we estimate the relative abundance of C₃/C₄ plants (i.e., the ratio of C₃ or C₄ biomass to local primary production) in modern vegetation for each region. The relative abundance of modern C₃/C₄ vegetation from each region is compared to the corresponding climatic parameters (mean annual temperature and precipitation) to explore the relationship between relative C₄ abundance and climate. The results indicate that temperature controls the growth of C₄ plants. However, even where temperature is high enough for the growth of C₄ plants, they will only dominate the landscape when precipitation declines as temperatures increase. Our results are consistent with those of other investigations of the geographic distribution of modern C₄ plant species. Therefore, our results provide an important reference for interpretation of past C₃/C₄ relative abundance records in these three regions.     

Temperature variability since A.D. 1837 inferred from tree-ring maximum density of <Emphasis Type="Italic">Abies fabri</Emphasis> on Gongga Mountain,China

Two tree-ring MXD (maximum latewood density) chronologies of Abies fabri were developed from the eastern slopes of Gongga Mountain, and a regional chronology (RC) was established based on the two MXD chronologies. There were significant positive correlations between the three MXD chronologies and August–September temperature, and the RC had the highest correlation (r=0.733, n=48, P<0.001) with mean August–September temperature. Based on growth-climate analyses, we reconstructed mean August–September temperature during the past 171 years for the study area. The reconstruction explained 53.5% of the instrumental temperature variance during the period 1960–2007 (F=52.8, R²_adj =52.4%). In the past 171 years, there were 22 very warm years and 23 very cold years, four cold periods (1837–1842, 1884–1891, 1899–1905 and 1984–1989) and three warm periods (1966–1973, 1916–1924 and 1876–1881). Our reconstruction was validated by other tree ring-based temperature reconstructions from the surrounding area and documented climate disaster events.     

高丰度硼-10制备过程中的液相络合剂

高丰度硼-10主要是通过精馏与化学交换法进行制备，在交换反应过程中，液相络合剂的研究非常重要．为此以苯甲醚、硝基甲烷、丙酮、甲基异丁基酮作为络合刑进行了系统的实验研究．设计了合成络合物体系的实验反应器，并用这些络合荆分别与三氟化硼合成了4种络合物体系．对这4种络合物体系的密度、凝固点、BF3／络舍剂比率以及蒸气压等性能进行了实验研究，并拟合了蒸气压随温度变化的曲线，通过分析认为苯甲醚更适宜于应用在硼同位素的分离过程中，能减少能耗，降低成本．     

Structural investigation and luminescent properties of BaZr(BO<Subscript>3</Subscript>)2:Eu<Superscript>3+</Superscript> phosphors containing Si

Si⁴⁺-doped BaZr(BO₃)₂:Eu³⁺ phosphors are prepared by a conventional solid-state reaction. The influence of Si⁴⁺ addition on the charge transfer state of Eu³⁺-O^2– and photoluminescence (PL) properties of BaZr(BO₃)₂:Eu³⁺ are discussed. Room temperature PL spectra indicated that efficient emission is obtained by Si doping. Increased values for the peak-peak ratio (PPR) of BaZr(BO₃)₂:Eu³⁺ at higher Si doping concentrations implied that the Eu³⁺ ion is located in a more asymmetric environment in BaZr_0.8Si_0.2(BO₃)₂:Eu³⁺ than in the undoped samples. The Judd-Ofelt parameters Ω_λ (λ=2,4) were calculated from the PL data, giving results that were consistent with those from the PPR. The maximum radiative quantum efficiency was achieved at a Si doping concentration of 20 mol%.