Evaluation of boron isotopes and trace element abundances in planktonic foraminifers as palaeo-oceanographic proxies

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Carbon isotopic fractionations during Fischer-Tropsch synthesis

To understand the carbon isotope fractionation during the mineral-catalyzed Fischer-Tropsch synthesis of hydrocarbons under hydrothermal conditions, experiments on formic acid were carried out at 300°C and 35 MPa using gold tubes in the presence of Fe as a catalyst. The experiments were composed of two groups: with and without water. Due to the limited volume of the gold tubes, only methane was available for isotopic analyses among all produced hydrocarbons. The results demonstrate that CO2 is the gas most enriched in 13C whereas methane is the gas most depleted in 13C. Moreover, methane becomes more and more depleted in 13C with an increase in reaction time. The carbon isotopic fractionation between CO2 and CH4 (α(CO2-CH4)) reached 1.052–1.059 at 144 h, which is similar to those of microbial reduction of CO2 to CH4 by methanogenic bacteria (1.048–1.079). This implies that carbon isotopic fractionation during Fischer-Tropsch synthesis is controlled by kinetic isotopic effects. Key words: Fischer-Tropsch synthesis, carbon isotope, isotope fractionation, abiogenic alkane ga

Fingerprint analysis of eucommia bark by LC-DAD and LC-MS with the aid of chemometrics

Chromatographic fingerprints of 46 Eucommia Bark samples were obtained by liquid chromatography-diode array detector (LC-DAD). These samples were collected from eight provinces in China, with different geographical locations, and climates. Seven common LC peaks that could be used for fingerprinting this common popular traditional Chinese medicine were found, and six were identified as substituted resinols (4 compounds), geniposidic acid and chlorogenic acid by LC-MS. Principal components analysis (PCA) indicated that samples from the Sichuan, Hubei, Shanxi and Anhui—the SHSA provinces, clustered together. The other objects from the four provinces, Guizhou, Jiangxi, Gansu and Henan, were discriminated and widely scattered on the biplot in four province clusters. The SHSA provinces are geographically close together while the others are spread out. Thus, such results suggested that the composition of the Eucommia Bark samples was dependent on their geographic location and environment. In general, the basis for discrimination on the PCA biplot from the original 46 objects× 7 variables data matrix was the same as that for the SHSA subset (36 × 7 matrix). The seven marker compound loading vectors grouped into three sets: (1) three closely correlating substituted resinol compounds and chlorogenic acid; (2) the fourth resinol compound identified by the OCH3 substituent in the R4 position, and an unknown compound; and (3) the geniposidic acid, which was independent of the set 1 variables, and which negatively correlated with the set 2 ones above. These observations from the PCA biplot were supported by hierarchical cluster analysis, and indicated that Eucommia Bark preparations may be successfully compared with the use of the HPLC responses from the seven marker compounds and chemometric methods such as PCA and the complementary hierarchical cluster analysis (HCA)

Tight gas in China and its significance in exploration and exploitation

Tight gas reservoirs refer to the tight sandstone fields or traps accumulating natural gas of commercial values. According to reservoir characteristics, reserves, and structural height, they can be divided into two types, continuous-type and trap-type: the former are located at the lower part of the structure and have indistinct trap boundaries, inconsistent gas-water boundaries and reversal of gas and water, and their reservoirs are the same as or near the source; the latter are located at the higher part of the structure, with gas above water in traps, low reserves, and relatively high production. Tight gas in China is all coal-derived, dominantly alkane gases (C1–4), in which the amount of methane is greatest and the alkane gases have positive carbon isotopic series. The content of non-hydrocarbon gases (mainly CO2 and N2) is low. At the end of 2010, the reserves and annual production of tight gas in China accounted for 39.2% and 24.6% of the total natural gas, respectively, and the proportions are expected to increase. Compared to the shale gas and coalbed gas, tight gas should be considered in priority in the exploration and exploitation of unconventional gas in China. Key words: China, large tight gas field, geochemical characteristics, gas source, coal-derived gas, exploration and exploitation, priorit

Fingerprinting of complex mixtures with the use of high performance liquid chromatography, inductively coupled plasma atomic emission spectroscopy and chemometrics

The molecular and metal profile fingerprints were obtained from a complex substance, Atractylis chinensis DC—a traditional Chinese medicine (TCM), with the use of the high performance liquid chromatography (HPLC) and inductively coupled plasma atomic emission spectroscopy (ICP-AES) techniques. This substance was used in this work as an example of a complex biological material, which has found application as a TCM. Such TCM samples are traditionally processed by the Bran, Cut, Fried and Swill methods, and were collected from five provinces in China. The data matrices obtained from the two types of analysis produced two principal component biplots, which showed that the HPLC fingerprint data were discriminated on the basis of the methods for processing the raw TCM, while the metal analysis grouped according to the geographical origin. When the two data matrices were combined into a one two-way matrix, the resulting biplot showed a clear separation on the basis of the HPLC fingerprints. Importantly, within each different grouping the objects separated according to their geographical origin, and they ranked approximately in the same order in each group. This result suggested that by using such an approach, it is possible to derive improved characterisation of the complex TCM materials on the basis of the two kinds of analytical data.\ud \ud In addition, two supervised pattern recognition methods, K-nearest neighbors (KNNs) method, and linear discriminant analysis (LDA), were successfully applied to the individual data matrices—thus, supporting the PCA approach

Discussion on the gas source of the Triassic Xujiahe Formation tight sandstone gas reservoirs in Yuanba and Tongnanba, Sichuan Basin: An answer to Yin Feng et al.

Gas-source correlation is generally focused on the genetic type of the main gas components, dominantly oil-associated gas or coal-derived gas. Gases from the Yuanba and Tongnanba gas reservoirs are dominated by methane with an average content of 95.36%. The average contents of ethane, propane, butane are 1.60%, 0.29% and 0.09%, respectively. In general, for the Yuanba and Tongnanba gas reservoirs, alkane gas has an average content of 97.34%, and CO2 has an average content of 0.63%, which only accounts for 6.5‰ of the methane. According to the discrimination criteria that δ13C2 value is greater than −28‰ for coal-derived gas and lower than −28.5‰ for the oil-associated gas, Yin et al. suggested that the gases from the Yuanba gas reservoir be a mixture of coal-derived and oil-associated gases, and the gases from the Tongnanba gas reservoir be oil-associated gas. However, the discrimination criteria of δ13C2 for coal-derived and oil-associated gases are only valid when the alkane gases have not undergone secondary alteration and have positive carbon isotopic series among C1–C4 alkanes. Hence, it is concluded that gases from the Yuanba and Tongnanba gas reservoirs are coal-derived gases due to their high content and heavy carbon isotopic values of methane (−31.3‰), which is typical for high mature coal-derived gases in the world. Though Yin et al. suggested that abiogenic CO2 of these two reservoirs is originated from metamorphism or hydrolysis of deep carbonate rocks, we proposed that these CO2 gases are self-generated and self-accumulated under the corrosion of calcarenaceous sandstone of the Triassic Xujiahe Formation. Key words: Yuanba gas reservoir, Tongnanba gas reservoir, tight sandstone gas, Triassic Xujiahe Formation, carbon isotopic composition, coal-derived ga

Accurate and precise isotopic measurement of sub-nanogram sized samples of foraminiferal hosted boron by total evaporation NTIMS

We report a total evaporation negative ion thermal mass spectrometry (TE-NTIMS) technique that enables precise and accurate (± 0.7‰; 2 s.d.) measurements of boron isotope ratios. The fundamental advantage of TE-NTIMS is that the effect of instrumental mass fractionation is minimised and sample signal maximised by analysing samples to exhaustion. We can analyse as little as 300 pg of B, which enables repeat analyses of dissolutions of small numbers of foraminifera (as little as 0.1 mg or ∼10 individual foraminfera). This represents a several fold reduction in the number of tests required compared to previous NTIMS studies and brings the amount of sample into line with other commonly used paleo-proxies. Standard addition experiments indicate that the 11B / 10B ratio of the NIST SRM 951 standard is not biased by differing amounts of seawater or carbonate matrix and yield an 11B / 10B within error of the certified value. We also show that our sample preparation induces no additional variations (e.g. blank contribution) beyond our analytical uncertainty. We obtain 11B / 10B ratios for seawater within error of values obtained using plasma ionisation, positive and negative thermal ionisation mass-spectrometry. Our measurements of core-top G. sacculifer from three ocean basins yield δ11B within analytical error (23.3–24.3‰) and fall within the range of published values. This study, however, further highlights significant interlaboratory biases in isotopic compositions of core-top foraminifera. Significantly, we show that our approach is not influenced by processing blank nor systematic differences in mass bias between measurements of sample and standard, which has yet to be documented for some other laboratories

Geochemical characteristics and distribution of CO2 gas fields in Bohai Bay Basin

Eleven CO2 gas fields (pools) have been discovered in the Huanghua and Jiyang Depressions of Bohai Bay Basin, Eastern China. The analyses of natural gas geochemical data in the CO2 gas fields (pools) reveal the following: First, there is a positive correlation between CO2 content, δ13CCO2 values, and R/Ra values but a negative correlation between CO2 content and CH4 content; Second, the elevated δ13CCO2, R/Ra, and 40Ar/36Ar values show that CO2 is mantle-derived; Third, organic and inorganic alkane gases are both discovered in the CO2 gas fields of the Huanghua Depression, and the alkane gas in the Jiyang Depression is mainly oil-type. Taking the geological background of the region into consideration, the article concludes that the high geothermal field region, intersection part of faults, magmatic rock region, and high R/Ra values region are favorable abundance zones for CO2 gas fields (pools). Key words: Bohai Bay Basin, CO2 gas field (pool), CO2 origin, geochemical characteristics, fault, helium isotop

Los actos intrínsecamente malos y la enseñanza de la encíclica «Veritatis Splendor»

We have assessed the reliability of several foraminifer-hosted proxies of the ocean carbonate system (δ 11B, B/Ca, and U/Ca) using Holocene samples from the Atlantic and Pacific oceans. We examined chemical variability over a range of test sizes for two surface-dwelling foraminifers (Globigerinoides sacculifer and Globigerinoides ruber). Measurements of δ 11B in G. ruber show no significant relationship with test size in either Atlantic or Pacific sites and appear to provide a robust proxy of surface seawater pH. Likewise there is no significant variability in the δ 11B of our Atlantic core top G. sacculifer, but we find that δ 11B increases with increasing test size for G. sacculifer in the Pacific. These systematic differences in δ 11B are inferred to be a consequence of isotopically light gametogenic calcite in G. sacculifer and its preferential preservation during postdepositional dissolution. The trace element ratio proxies of ocean carbonate equilibria, U/Ca and B/Ca, show systematic increases in both G. ruber and G. sacculifer with increasing test size, possibly as a result of changing growth rates. This behavior complicates their use in paleoceanographic reconstructions. In keeping with several previous studies we find that Mg/Ca ratios increase with increasing size fraction in our well-preserved Atlantic G. sacculifer but not in G. ruber. In contrast to previous interpretations we suggest that these observations reflect a proportionally larger influence of compositionally distinct gametogenic calcite in small individuals compared to larger ones. As with δ 11B this influences G. sacculifer but not G. ruber, which has negligible gametogenic calcite