Inter‐laboratory Characterisation of Apatite Reference Materials for Chlorine Isotope Analysis

Here we report on a set of six apatite reference materials (chlorapatites MGMH#133648, TUBAF#38 and fluorapatites MGMH#128441A, TUBAF#37, 40, 50) which we have characterised for their chlorine isotope ratios; these RMs span a range of Cl mass fractions within the apatite Ca₁₀(PO₄)₆(F,Cl,OH)₂ solid solution series. Numerous apatite specimens, obtained from mineralogical collections, were initially screened for ³⁷Cl/³⁵Cl homogeneity using SIMS followed by δ³⁷Cl characterisation by gas source mass spectrometry using both dual‐inlet and continuous‐flow modes. We also report major and key trace element compositions as determined by EPMA. The repeatability of our SIMS results was better than ± 0.10‰ (1s) for the five samples with > 0.5 % m/m Cl and ± 0.19‰ (1s) for the low Cl abundance material (0.27% m/m). We also observed a small, but significant crystal orientation effect of 0.38‰ between the mean ³⁷Cl/³⁵Cl ratios measured on three oriented apatite fragments. Furthermore, the results of GS‐IRMS analyses show small but systematic offset of δ³⁷Cl_SMOC values between the three laboratories. Nonetheless, all studied samples have comparable chlorine isotope compositions, with mean 10³δ³⁷Cl_SMOC values between +0.09 and +0.42 and in all cases with 1s ≤ ± 0.25.     

浅层工程地震层析成像技术的应用研究

本文由射线理论出发,简要地阐述了浅层折射地震层析成像方法的原理,并给出了应用实例     

大气季节内振荡对印度洋—西太平洋地区热带低压/气旋生成的影响

文中利用EOF分析大气季节内振荡 (MJO)的时空变化的方法 ,研究了 1996年 9月～ 1997年 6月间的MJO活动对生成在印度洋—西太平洋海域的热带低压 /气旋的影响。结果发现 ,除西北太平洋之外 ,发生在其他区域的热带低压 /气旋有半数以上生成在向东移动的MJO的湿位相中。伴随MJO的向东传播 ,热带低压 /气旋平均生成位置也随之向东移动 ,而生成在西北太平洋的热带低压 /气旋分别受到向东和向西传播的MJO影响     

Li2SO4溶液中离子间的缔合相互作用:基于密度泛函理论和分子动力学模拟的研究

基于密度泛函理论,使用B3LYP/aVDZ方法对[Li_2SO_4(H_2O)_n]~0(n=0~10、18)水合团簇的结构和性质进行了系统地研究,并结合Car-Parrinello分子动力学(CPMD)模拟了不同浓度的Li_2SO_4溶液结构,目的在于理解在Li_2SO_4溶液中离子间缔合相互作用及可能存在的物种。研究发现,对于[Li_2SO_4(H_2O)_n]~0(n=0~10、18)水合团簇,双配位单齿螯合接触离子对结构比双配位双齿螯合接触离子对结构更稳定,溶剂共享离子对结构最不稳定。同时,CPMD模拟结果表明,在3.09和3.17 mol/kg的Li_2SO_4溶液中,双配位单齿螯合接触离子对结构仍然是主要物种。以上结果表明在饱和的Li_2SO_4溶液(3.16 mol/kg)中,Li~+和SO_4~(2-)离子间的相互缔合作用主要以双配位单齿螯合接触离子对结构的物种存在,而具有双配位双齿螯合离子对结构的物种占少数,溶剂共享离子对结构几乎不存在。     

磺酸型阳离子树脂的元素分配行为及高精度同位素分析应用

不同元素在离子交换树脂的分配系数是元素纯化和分离的基础,不同酸中各元素分配系数差异可用于设计高效的元素提纯流程,从而被广泛应用于现代高精度同位素分析。本文以AG®50W-X8阳离子树脂为研究对象,以分配系数(Kd)作为量化指标,通过系统实验研究不同元素在该树脂中的分配行为。在前人研究基础上,本实验增加了元素数量和酸的种类,涵盖了金属、类金属、非金属和稀土元素。结果表明：在盐酸和硝酸介质中,几乎所有元素的Kd都与酸度呈负相关,当酸度达到6mol/L时,除Th和Ca以外的所有元素都会被酸洗脱。稀土元素(REEs)和高场强元素在0.1～0.5mol/L稀硝酸和稀盐酸中强烈吸附在树脂上;而一些过渡金属、类金属和非金属元素(如Mo、W、Re、Ir、Sb、Ge、As、Se、Te等)在酸溶液中会形成含氧阴离子,不与阳离子树脂发生吸附。Al、Fe、Se、Pd、Cd、In等元素在盐酸中易与氯离子形成配位化合物或离子团,导致这些离子在盐酸中的分配系数显著降低。在硝酸和盐酸与氢氟酸的混合酸中,除稀土元素外,绝大部分元素随酸度增加Kd迅速降低。稀土元素在盐酸-氢氟酸混合介质中,随着盐酸的浓度增加(从0.1mol/L盐酸-0.2mol/L氢氟酸至6mol/L盐酸-0.2mol/L氢氟酸),稀土元素分配系数（KdREE）具有先增加后降低的趋势。氢氟酸的加入可显著降低Be、Al、Sc、Fe、Sn、Th、U、Ti、Zr、Hf等元素在稀盐酸和稀硝酸中的分配系数,使这些元素几乎不与树脂发生吸附。本研究揭示了不同酸介质中各类元素在阳离子交换树脂上的分配行为存在差异,尤其是氢氟酸的加入可显著改变高场强元素、部分过渡金属和稀土元素的分配系数,为应用该树脂开发和优化适用于高精度金属稳定同位素分析的元素提纯流程(如Li、Mg、K、Sr、Ce、U等)提供了数据支撑,并可有效地减少后续实验设计的工作量。     

Propagation of Extremely Low Frequency Waves Through the Ionosphere

The propagation features of extremely low frequency electromagnetic waves through the multicomponent ionospheric plasma are studied. It is shown that at relatively lower frequencies refractive index for right hand mode is higher than the left-hand mode, which is reversed at higher frequencies. The thermal temperature of plasma particle causes decrease in phase and group velocities of both right and left-hand modes. The crossover frequencies for different plasma models are computed and variation with ion concentration and thermal velocity is studied. Explicit expression for group velocity and travel time has been derived and studied numerically. Finally, we have presented simulation of the ion whistler spectrograms for Hydrogen, Helium and Oxygen ions present in the ionospheric plasma. The results are compared with the experimentally detected hydrogen and helium ion whistlers. The importance of the present study in the exploration of ionospheric plasma is illustrated.     

Simultaneous Determination of Fluorine,Chlorine, Bromine and Iodine in Six Geochemical Reference Materials Using Pyrohydrolysis,Ion Chromatography and Inductively Coupled Plasma‐Mass Spectrometry

Concentrations of halogens (fluorine, chlorine, bromine and iodine) were determined in six geochemical reference materials (BHVO‐2, GS‐N, JG‐1, JR‐1, JB‐1b, JB‐2). Halogens were first extracted from powdered samples using a pyrohydrolysis technique, then hydrolysis solutions were analysed by ion chromatography for F and Cl and inductively coupled plasma‐mass spectrometry for Br and I. The detection limits in solutions were 100 μg l^?1 for both F and Cl and 10 ng l^?1 for Br and I. Considering the extraction procedure, performed on a maximum of 500 mg of sample and producing 100 ml of pyrohydrolysis solution, detection limits in rock samples were 20 mg kg^?1 for F and Cl and 2 μg kg^?1 for Br and I. The mean analytical errors on the studied composition ranges were estimated at 10 mg kg^?1 for F and Cl, 100 μg kg^?1 for Br and 25 μg kg^?1 for I. The concentration values, based on repeated (generally > 10) sample analysis, were in good agreement generally with published values and narrowed the mean dispersion around mean values. Large dispersions are discussed in terms of samples heterogeneity and contaminations during sample preparation. Basaltic RMs were found to be more suitable for studies of halogen compositions than differentiated rock material, especially granites – the powders of which were heterogeneous in halogens at the 500 mg level.     

土壤样品镉同位素分析中Cd与Sn有效分离方法的改进

保证Cd的高回收率以及彻底的Sn干扰去除是获得精确镉同位素组成的前提,目前报道的多种Cd分离与纯化方法获得的Cd回收率有较大差异(42.6%~99.8%),且去除Sn干扰的效果也不同(去除率在87.8%~97.4%之间),Cd回收率和Sn去除率均不理想。本文对前人报道的分离方法进行对比实验,发现0.1 mol/L氢溴酸-0.5 mol/L硝酸是分离Cd和Sn的有效试剂,增加该组混合酸的用量可淋洗出样品中更多的Sn且不会损失Cd,当混合酸的淋洗用量增加至30 mL时,Sn的淋洗率达到99.8%以上,Cd的回收率亦达到99.0%±0.5%,可满足土壤样品镉同位素的测定要求。本工作为获得高精度的镉同位素组成奠定了基础,为研究土壤环境中镉的污染来源提供了技术手段。     

A New Approach for Border Detection of the Dumluca (Turkey) Iron Ore Area: Wavelet Cellular Neural Networks

Anomaly analysis is used for various geophysics applications such as determination of geophysical structure's location and border detections. Besides the classical geophysical techniques, artificial intelligence based image processing algorithms have been found attractive for geophysical anomaly analysis. Recently, cellular neural networks (CNN) have been applied to geophysical data and satisfactory results are reported. CNN provides fast and parallel computational capability for geophysical image processing applications due to its filtering structure. The behavior of CNN is defined by two template matrices that are adjusted by a properly supervised learning algorithm. After training stage for geophysical data, Bouguer anomaly maps can be processed and analyzed sequentially. In this paper, CNN learning and processing capability have been improved, combining Wavelet functions and backpropagation learning algorithms. The new architecture is denoted as Wavelet-Cellular Neural networks (Wave-CNN) and it is employed to analyze Bouguer anomaly maps which are important to extract useful information in geophysics. At first, Wave-CNN performance is tested on synthetic geophysical data, which are created by a computer environment. Then, Bouguer anomaly maps of the Dumluca iron ore field have been analyzed and results are reported in comparison to real drilling results.     

Synthesis of Pb-Feldspar by Ion Exchange Reaction and Its Implications

Feldspar and Pb（NO3）2 were mixed and reacted at T=380℃ to synthesize Pb-feldspar. In the XRD （X-ray diffraction） pattern of the product, the d values （crystal lattice spacing） of the five peaks are 0.654, 0.342, 0.332, 0.327 and 0.257 nm. The XPS analysis results show that the binding energy of Pb 4f（7/2） in the feldspar was between 137.81-138.03 eV. Pb^2＋ can replace alkali and alkali earth cations in the feldspar structure through ion exchange reaction to form Pb-feldspar.