Hf isotope composition of zircons and implication for the petrogenesis of Yajiangqiao granite,Hunan Province,China

In the peralumineous granite of Yajiangqiao zircon population can be divided into two groups (i.e. Zircon Ⅰ and Zircon Ⅱ), which were formed in magmatic chamber and in emplacement place, respectively. The Hf isotope compositions of two stages of zircon show that the host magma was essentially derived from crustal material by melting. However, some higher 176Hf/177Hf ratios indicate that the granitic zircons should contain fine crystal of zircon formed in mantle-derived magma. In fact, the backscattered electron imaging and the electron microprobe analysis reveal that there is another type of zircon included within Zircon Ⅰ, which is quite different from Zircon Ⅰ and Zircon Ⅱ in morphology and chemistry. They are considered to be the product of the mantle-derived magma intruded into the granitic magma chamber at the beginning of anatexis. Thus,it is suggested that the formation of Yajiangqiao granite is related to the underplating of mantle magma.     

Isotope effect for transport and magnetic properties of La 0.35 Pr 0.35 Ca 0.3 MnO 3 thin films

The effect of ¹⁶ O → ¹⁸ O isotope substitution on electrical resistivity, magnetoresistance, and ac magnetic susceptibility was studied for La_0.35Pr_0.35Ca_0.3MnO₃ epitaxial thin films deposited onto LaAlO₃ and SrTiO₃ substrates. For the films on LaAlO₃, the isotope substitution resulted in the reversible transition from a metal-like to insulating state. The applied magnetic field ( H ≥ 2 T) transformed the sample with ¹⁸O back to the metallic state. The films on SrTiO₃ remained metallic at low temperatures for both ¹⁶O and ¹⁸O, but the shift of the resistivity peak corresponding to onset of metallic state exceeded 63 K after ¹⁶ O → ¹⁸ O substitution. The temperature dependence of both resistivity and magnetic susceptibility was characterized by hysteresis, especially pronounced in the case of the films on LaAlO₃. Such a behavior gives certain indications of the phase separation characteristic of interplay between ferromagnetism and charge ordering. Received 11 February 2000 and Received in final form 13 September 2000     

Discussion of gas enrichment mechanism and natural gas origin in marine sedimentary basin,China

There are abundant natural gas resources in Chinese marine sedimentary basin. The exploration hot shots of natural gas are the Palaeozoic marine strata here in recent years, and several large scale gas fields have been discovered. Chinese Palaeozoic high-post matured and coal measure hydrocarbon source rocks are mainly prone to gas generation in the present. This research considered that gas source rocks and TSR are the key cause of gas enrichment of marine strata. High-quality argillaceous and coal measure hydrocarbon rocks are distributed widely in the Palaeozoic marine strata, which have been in highly matured phase in the present. The argillaceous source rock generally contains various sulfates that could accelerate crude oil cracking to gas for TSR occurrence, and coal measure source rock mainly generates gas, so Chinese marine basin gives priority to accumulating gas. Marine strata have not founded oil reservoirs in the Sichuan Basin and Ordos Basin, and they consist mainly of dry gas. Marine natural gases are the mixed gases of oil cracking gas and coal-formed gas in a general way, oil cracking gases contain usually some H2S and CO2. Hydrocarbon carbon isotopes are very complicated, and methane and ethane isotopic values bear apparent reversal caused by thermal evolution and mixing among different genetic types of natural gas. Coal-formed gases are the main component of Chinese marine natural gas. The Upper Permian of the Sichuan Basin and the Carboniferous-Permian of the Ordos Basin coal measure hydrocarbon source rock present large hydrocarbon generation potential, which are the prospecting highlight of marine natural gas hereafter. Oil cracking gas exploration will be paid much attention to in the Tarim Basin because of the lack of coal measure hydrocarbon source rock.     

Diet control on carbon isotopic composition of land snail shell carbonate

Carbon isotope compositions for both the carbonate shells and soft bodies (organic tissue) of living land snails collected mostly from the Loess Plateau, China have been measured. The result shows that δ 13C values range from -13.1‰ to -4.3‰ for the aragonite shell samples and from -26.8‰ to -18.0‰ for the soft body samples. Although the shells are enriched in 13C relative to the bodies averagely by 14.2(±0.8)‰, the shell δ 13Ca values are closely correlated to the body δ 13Corg values, expressed as δ 13Ca = 1.021 δ 13Corg 14.38 (R = 0.965; N = 31). This relationship indicates that δ 13Ca is primarily a function of the isotopic composition of the snail diets since previous studies have proved that the snail body is the same as their food in carbon isotope composition. In other words, carbon isotope compo-sition of the carbonate shell can be used as a proxy to estimate the dietary 13C abundance of the land snails. The data also support that the 13C enrichment of the carbonate shells results mainly from the equilibrium fractionations between the metabolic CO2, HCO3-in the hemolymph and shell aragonite, and partially from kinetic fractionations when snail shells form during their activity.     

Authigenic sulfide minerals and their sulfur isotopes in sediments of the northern continental slope of the South China Sea and their implications for methane flux and gas hydrate formation

This is a report of the study of the authigenic sulfide minerals and their sulfur isotopes in a sediment core (NH-1) collected on the northern continental slope of the South China Sea, where other geo-physical and geochemical evidence seems to suggest gas hydrate formation in the sediments. The study has led to the findings: (1) the pyrite content in sediments was relatively high and its grain size relatively large compared with that in normal pelagic or hemipelagic sediments; (2) the shallowest depth of the acid volatile sulfide (AVS) content maximum was at 437.5 cm (>2 μmol/g), which was deeper than that of the authigenic pyrite content maximum (at 141.5-380.5 cm); (3) δ 34S of authigenic pyrite was positive (maximum: 15‰) at depth interval of 250-380 cm; (4) the positive δ 34S coincided with pyrite enrichment. Compared with the results obtained from the Black Sea sediments by Jorgen-sen and coworkers, these observations indicated that at the NH-1 site, the depth of the sulfate-methane interface (SMI) would be or once was at about 437.5-547.5 cm and the relatively shallow SMI depth suggested high upward methane fluxes. This was in good agreement with the results obtained from pore water sulfate gradients and core head-space methane concentrations in sediment cores collected in the area. All available evidence suggested that methane gas hydrate formation may exist or may have existed in the underlying sediments.     

用HI-13串列加速器质谱装置测量182Hf的研究

¹⁸²Hf的半衰期为(8.90±0.09)Ma, 是一个接近灭绝的放射性核素. 超新星爆炸是自然界中已知的惟一能产生¹⁸²Hf的途径. 因此¹⁸²Hf是研究近1亿年来在地球附近可能发生的超新星事件的理想核素. 另外, ¹⁸²Hf是核工程中特别感兴趣的一个长寿命放射性核素. 精确测量超痕量的¹⁸²Hf对反应堆的设计和核天体物理学以及其他研究领域都是非常重要的. 用加速器质谱有可能实现对超低含量¹⁸²Hf的测量. 在中国原子能科学研究院的HI-13加速器质谱装置上对¹⁸²Hf的测量方法以及样品的化学去钨方法进行了研究, 分别得到了空白样品以及系列标准样品的¹⁸²Hf和¹⁸³W的能量-飞行时间双维谱. ¹⁸²W对¹⁸²Hf计数的贡献是通过测量¹⁸³W的计数归一扣除的. 目前本工作对¹⁸²Hf的测量灵敏度为4.15±10^－11 (¹⁸²Hf/¹⁸⁰Hf比值).     

LIST developments at IGISOL

The ion guide technique was developed in Jyv?skyl? during the early 1980's. In the ion guide the reaction recoil products are stopped and thermalized in high purity helium gas where they remain ionic due to high ionization potential of helium atoms. Different designs of ion guide exist for light-ion induced fusion reactions, for heavy-ion induced fusion and for proton induced fission. Although the IGISOL method is fast and universal it is chemically unselective and in many cases relatively inefficient. In order to address these deficiencies in the technique, a new laser ion source project, FURIOS (Fast Universal Resonant laser Ion Source), commenced in 2004. In addition, resonance ionization spectroscopy has been tested off – line within a sextupole ion beam guide.     

热熔合反应合成超重核产生截面的同位素依赖性

通过在形成超重核的重离子俘获和熔合过程中引入位垒分布函数的方法对双核模型做了进一步发展. 超重核形成过程中的俘获、熔合和蒸发3个阶段分别采用了半经验的耦合道模型、数值求解主方程和统计蒸发模型的方法来描述. 计算了近年来Dubna小组利用热熔合反应⁴⁸Ca(²⁴³Am, 3n—5n)^288—286115和⁴⁸Ca(²⁴⁸Cm, 3n—5n)^293—291116合成超重新核素的蒸发余核激发函数. 系统分析了⁴⁸Ca轰击锕系元素U,Np,Pu,Am,Cm合成超重核Z=112—116产生截面的同位素依赖性. 给出了合成超重新核素最佳的弹靶组合和入射能量, 即有最大的超重核产生截面. 计算说明, 壳修正能和中子分离能是影响超重核生成截面产生同位素依赖性的主要因素.     

北海市经济贝类基本成分和碳氮生源要素含量测定分析

广西沿海贝类资源丰富，在海洋渔业和海洋生态系统中意义重大。为获取用于开展贝类增养殖容量评估，构建食物链网、生源要素和能量流动模型，以及开展北部湾海域海洋牧场建设和碳汇渔业评估的基础数据，本研究对北海市常见的14种经济贝类进行相关数据的测定与分析。实验对从北海市市场收集的14种经济贝类的壳长(SL)、壳宽(SW)或壳高(SH)、体质量(BM)、壳质量(SM)、软体部质量(MSP)进行测量，并同时对软体部的水分、粗蛋白、能量、碳和氮的含量及稳定同位素丰度等进行测定。实验结果表明，不同贝类的出肉率差别较大，贝壳较薄的大獭蛤(Lutraria maxima)和缢蛏(Sinonovacula constricta)等可超过70%。双壳贝类的软体部含水率均超过85%，腹足类的软体部含水率不超过81%。贝类的有机碳含量为39.77%-47.36%，氮含量为8.25%-11.80%。双壳贝类中尖紫蛤(Soletellina acuta)δ¹³C最低,华贵栉孔扇贝(Chalamys nobilys)的δ¹³C最高；双壳贝类中华贵栉孔扇贝的δ¹⁵N最低,等边浅蛤(Macridiscus aequilatera)的δ¹⁵N最高。软体部能量含量为16.11-20.81 kJ/g。双壳贝类软体部能量含量(E,kJ)与其壳长(SL,cm)的关系符合指数模型E=a×e^b×SL,腹足类软体部能量含量(E,kJ)与其壳高(SH,cm)的关系符合指数模型E=a×e^b×SH；软体部能量含量(E,kJ)与体质量(BM,g)的关系符合线性公式E=a×BM+b。不同种类的贝类的基本成分和生源要素的特征存在差异，与已有文献报道不同海区的同种贝类相关数据也存在较大差异。因此，在进行生态学相关研究时，数据的收集非常重要，借鉴相关物种的数据要非常谨慎。     

Observation of single Ca ions for trace isotope analysis

We developed an ion trap — laser cooling system for observing the laser induced fluorescence (LIF) of a single ion, in the view of utilizing it for the trace isotope analysis of Ca. We observed stepwise LIF signals, which correspond to the numbers of trapped ⁴⁰Ca⁺ ions (⁴⁰Ca/Ca = 96.9%). The detection efficiency was evaluated and the observation of single ions demonstrated the experimental feasibility of trace isotope analysis. Furthermore, as the next step towards trace isotope analysis, we report observation of the even calcium isotopes, ⁴⁴Ca (⁴⁴Ca/Ca = 2.09%) and ⁴⁸Ca (⁴⁸Ca/Ca = 0.187%), without the use of a selective loading method.