Electrokinetic in rocks: Laboratory measurements in sandstone and volcanic samples

The streaming potential due to fluid flow in rocks was measured on saturated sandstones. During triaxial failure test, the electrokinetic coupling coefficient was increased at about 72–86% of the failure stress. This increase is thought to be due to an increase of the macroscopic zeta potential in the shear zone where new surfaces are created and connected, allowing fluid to flow through these new cracks. The streaming potential variations could therefore be used as a precursor of the rupture. Measurements were also performed on volcanic samples, with the aim of using electrokinetic phenomena to monitor volcanic activity. Streaming potential was found to depend on the transport properties i. e., permeability and formation factor. Theoretical consideration suggest that such a dependence should be caused by surface conductivity, but this is not the case here.     

A quantitative fluorescence technique for evaluating thermal maturity: Instrumentation and examples

Fluorescence microscopy is useful not only for identifying most of the oil-prone organic matter (macerals) in sedimentary rocks and coals but also for assessing their thermal maturities (ranks). This report introduces a violet-light excitation system which induces more than one order of magnitude stronger fluorescence intensity that the commonly used UV-light excitation system. The red/green quotient from violet-light excited fluorescence, Q_v, of sporinite can be easily measured using this system. Several examples using coal and cuttings samples are presented to demonstrate the use of this technique for evaluating the thermal maturities of coals and sedimentary rocks.From the results of our studies we conclude that:

• 1.(1) Violet-light excited fluorescence from sporinites can be routinely measured to assess thermal maturity.
• 2.(2) Spectral (Quantitative) fluorescence technique is useful for evaluating thermal maturity when samples are poorly polished or deficient in vitrinite.
• 3.(3) Visual (Strew-mounted) kerogen slides can not be used for fluorescence measurements unless a non-fluorescent mounting medium is used.

     

改进的卡洛斯管溶样等离子体质谱法测定地质样品中低含量铂族元素及铼的含量

报道了一个改进的卡洛斯管溶样等离子体质谱法测定地质样品中铂族元素及Re含量的新方法。将封闭的卡洛斯管置于高压釜中,然后在高压釜中加水,密封在高压釜中的水在高温下产生的外压将会抵消卡洛斯管中由酸产生的内压,这样就可以避免传统的卡洛斯管在高温高压下可能发生爆炸的危险。由此可以加大取样量,降低铂族元素测定过程中的块金效应及检出限,使超低含量铂族元素的测定成为可能。12g样品在75mL卡洛斯管中用35mL王水于320℃溶解15h,基本上可以使各种地质样品中的铂族元素矿物完全溶解。一次溶样可以测定全部铂族元素及Re,全流程空白值极低,国际标样测定结果稳定可靠。     

X-ray flurorescene (XRF) determination of trace rare-earth elements in geological samples using ion-exchange-resin membrane technique

Rare-earth elements in samples of geological interest were separated from other elements and concentrated onto ion-exchange membrane through ion-exchange procedures. The membrane was then used to determine the REE by X-ray fluorescence spectrography. In comparison with the traditional “thick-specimen” approach, the requirement of sample (REE oxides) in this method was reduced from 10 to 1 mg. Variable-internal-standard-quantification method was adopted to determine the relative concentrations of REE collected on the membrane. The area density of the sample was controlled at about 0.0003 g/cm², so that the matrix effect could be eliminated to a satisfactory extent. Interference calibration between the spectro-lines and the background determination was also improved, with the detection limit reaching 2.5×10^?6g.     

Three nonparametric techniques for the optimum discretization of quantitative geological variables

Three nonparametric techniques for the optimum discretization of quantitative geological features are proposed and demonstrated. The three methods are: isolated weight, entropy information, and rank correlation. Optimum discretization plays important roles in solutions to the following geoscience problems: (1) signal/noise separation and delineation of meaningful anomalies and other geofields related to mineral targets; (2) selection of those geological variables that explain variations in mineral resources; (3) determination of the best subintervals of values for a variable with respect to mineralization; (4) enhancement of certain complex and concealed information of a geofeature about its correlation with magnitude of mineralization; and (5) unification of diverse geodata so that these data can be integrated and analyzed.     

A comparison of lead-isotope measurements on exploration-type samples using inductively coupled plasma and thermal ionization mass spectrometry

Thermal ionization mass spectrometry (TI-MS) has long been the method of choice for Pb-isotope determinations. More recently, however, inductively coupled plasma mass spectrometry (ICP-MS) has been used to determine Pb-isotope ratios for mineral exploration. The ICP-MS technique, although not as precise as TI-MS, may promote a wider application of Ph-isotope ratio methods because it allows individual isotopes to be determined more rapidly, generally without need for chemical separation (e.g., Smith et al., 1984; Hinners et al., 1987). To demonstrate the utility of the ICP-MS method, we have conducted a series of Pb-isotope measurements on several suites of samples using both TI-MS and ICP-MS.     

Improvement of saponification extraction method for fatty acids separation from geological samples

The conventional saponification method could result in lower recoveries and artificial changes of long-chain fatty acids. The main reason is the error judgment of the intermediate layer suspended between the aqueous and organic layer during the liquid–liquid extraction process. This study shows that the intermediate layer consists of lots of medium- to long-chain carboxylic salts for their special physical and chemical properties. An improved saponification extraction method is also developed and the results show that the carboxylic salts distributed in the intermediate layer could be obtained completely, which greatly enhances the authenticity and accuracy of fatty acid analysis. Additionally, the possible reasons of formation of the intermediate layer are also discussed.     

Alpha-spectrometric determination of uranium and thorium in geological samples

Alpha-spectrometric technique is described as an independent method for determining micro-contents of U²³⁸ and Th²³². It is based on the comparison of alpha spectral activity of U²³⁸ and Th²³² in geological samples with that contributed by the U²³²·Th²²⁸ spike of known concentration. The experiment procedure consists of dissolving fine powdered samples with acid and adding a given amount of U²³²-Th²²⁸ spike. Uranium and thorium are then separated by ion exchange. After purification, each aliquot is mounted onto a separate stainless steel disk for measurement by alpha spectrometer, which consists essentially of a silicon surface barrier detector and a low noise amplification system connected to a multi-channel analyzer. After corrections for the background, tail and other factors, the desired U²³² and Th²³² concentrations can be calculated. The data obtained by the alpha-spectrometric method using U²³²-Th²²⁸ spike are compared with colorimetric determinations. Excellent agreement is obtained between the two sets of results. The coefficients of correlation are about 0.98 for U²³⁸ and 0.97 for Th²³². The accuracy of uranium and thorium analyses by this method depends primarily upon the counting statistics of U²³², U²³⁸ and Th²²⁸ and, to a certain extent, upon the calibration of U²³²-Th²²⁸ spike. Errors in uranium and thorium concentrations obtained by this method are generally within 2 to 5%.     

非传统稳定同位素锗的测试进展及其地质应用

Ge具有亲硫、亲铁、亲石和亲有机质的特性,被广泛应用于矿床学、环境科学等学科。然而,由于测试技术和手段的限制,Ge同位素在地球科学中的应用还很有限,但已显示出较好的应用潜力。本文在综合前人研究成果的基础上,结合笔者最新的研究工作,对Ge同位素的测试技术和手段等方面做了较全面的总结,内容包括Ge同位素化学前处理方法的研究进展、Ge同位素测试过程中仪器产生的质量歧视的校正方法。同时,亦对自然界样品中Ge同位素的组成、Ge同位素分馏机制及应用等方面做了评述。     

地质统计学在断层定量预测中的应用

断层 ,特别是１５ｍ以下的断层 ,一直是矿井开掘、回采的一大隐患。现在对构造预测的方法很多 ,如 :构造块段法 ,岩性分析法 ,物探方法等等。笔者从实用性和计算简单出发 ,采用地质统计方法来满足生产需要 ,此方法不一定最好 ,但愿能抛砖引玉。１引言地质统计学应用的核心问题是 :如何针对反映矿床特征的不同地质变量 ,构造出其空间分布的理论模型（即变差函数理论模型）,这是地质统计学中其它一切计算过程的基础。在建立样本函数时 ,样本中的个别特异值对变差函数的建立会带来麻烦 ,所以应对其影响进行消除 ,以免使拟合的理论变差函数受到…     

地质样品中铂族元素的分析测定方法

文中阐述并归纳了近年地质样品中铂族元素的分离、富集及测试方法方面的最新进展。铂族元素本身的超痕量性,要求实验过程中对空白值的控制,干扰元素的扣除和检测限的降低更为严格,同时要克服块金效应。文中对消解过程中常用的火试金法、酸溶、碱熔方法和卡洛斯管法(Carius tube),分离富集过程中的Te共沉淀和离子交换法,测试手段中的原子光谱法、中子活化法和等离子质谱法等方法的最新进展进行了总结。由于复杂的地质样品中PGE的浓度范围不一、赋存形式多样,要求在具体样品分析过程中灵活地搭配使用各种分离富集和检测方法,结合笔者所在实验室在实验过程中发现的问题,对各种不同类型地质样品中铂族元素的分离富集、样品处理及测定方法也进行了总结。     

地质样品Sr同位素激光原位等离子体质谱(LA-MC-ICP-MS)测定

Sr同位素在研究岩浆演化及其源区具有重要的示踪作用.MC-ICP-MS的出现为具有高Sr含量地质样品的激光原位Sr同位素测定变成了现实.本文利用Netpune MC-ICP-MS和193nm准分子激光联机,通过滨珊瑚、斜长石、磷灰石和钙钛矿等系列实验,建立了激光原位Sr同位素测定方法.实验结果表明,激光Sr同位素测定中Kr、Rb和稀土元素二价离子的干扰能够有效扣除,而钙聚合物的干扰在Neptune型MC-ICP-MS并不显著.不同激光参数的实验表明,大激光束斑产生更高信号强度,因而Sr同位素精度更高,同一激光束斑大小,激光脉冲频率对Sr同位素精度无明显影响.     

应用ICP-AES法测定地质样品中的砷和锑

本文采用ICP-AES方法,对地质样品中砷、锑的测定进行了研究,建立了一种准确测定土壤及金矿化岩石样品中砷、锑的方法。该方法准确、简便、快捷,采用基体匹配法消除了大量基体的干扰。而且,克服了常规原子荧光方法不能达到的高含量测定范围。此方法对5个国家标准样品进行了验证,12次测定精密度小于6%。     

非水滴定法测定地质样品中的总碳

提出了在乙醇-乙醇胺溶液中，用非水滴定法简便快速测定地质样品中的总碳的方法。经对国家一级标准物质分析，结果准确可靠，相对标准偏差（RSD，n=12）ω小于3．8％，方法检出限为0.011％。     

An anemometry technique for turbulence measurements at low velocities

A method using symmetrically bent V-shaped hot-wires has been developed for the accurate measurement of low-speed turbulence. Directional characteristics of V-shaped hot-wires at low velocities are investigated, and a generalized expression is derived for the effective cooling velocity. The measurement with V-shaped hot-wires in a pseudo turbulent field, which is artificially produced by shaking the hot-wires with an accurately known motion in a steady flow, has confirmed that the expression for the effective cooling velocity is also valid for instantaneous velocity fluctuations. The accuracy of a practical technique comprising two V-shaped hot-wires in an X arrangement is investigated by an error analysis in simulated Gaussian velocity fields using a digital computer.     

X射线荧光光谱法测定地质样品中的氯

使用粉末压片法制样,X射线荧光光谱法测定地质样品中氯,探讨了样片背衬、样片接受X光照射时间对测量结果的影响。Cl的精密度(RSD,n=12)小于10%。Cl的方法检出限为12μg/g,采用国家一级标准物质分析验证方法,其结果与标准值相符。     

New insights into the origin of perylene in geological samples

The origin of the polycyclic aromatic hydrocarbon (PAH) perylene in sediments and petroleum has been a matter of continued debate. Reported to occur in Phanerozoic organic matter (OM), fossil crinoids and tropical termite mounds, its mechanism of formation remains unclear. While a combustion source can be excluded, structural similarities to perylene quinone-like components present in e.g. fungi, plants, crinoids and insects, potentially suggest a product-precursor relationship. Here, we report perylene concentrations, ¹³C/¹²C, and D/H ratios from a Holocene sediment profile from the Qingpu trench, Yangtze Delta region, China. Perylene concentrations differ from those of pyrogenic PAHs, and rise to prominence in a stratigraphic interval that was dominated by woody vegetation as determined by palynology including fungal spores. In this zone, perylene concentrations exhibit an inverse relationship to the lignin marker guaiacol, D/H ratios between −284‰ and −317‰, similar to the methoxy groups in lignin, as well as co-variation with spores from wood-degrading fungi. ¹³C/¹²C of perylene differs from that of land plant wax alkanes and falls in the fractionation range expected for saprophytic fungi that utilise lignin, which is isotopically lighter than cellulose and whole wood. During progressive lignin degradation, the relative carbon isotopic ratio of the perylene decreases. We therefore hypothesise a relationship of perylene to the activity of wood-degrading fungi. To support our hypothesis, we analysed a wide range of Phanerozoic sediments and oils, and found perylene to generally be present in subordinate amounts before the evolutionary rise of vascular plants, and to be generally absent from marine-sourced oils, few exceptions being attributed perhaps to a contribution of marine and/or terrestrial-derived fungi, anoxia (especially under marine conditions) and/or contamination of core material by fungi. A series of low-molecular-weight aromatic quinones bearing the perylene-backbone were detected in Devonian and Cretaceous sediments, potentially representing precursor components to perylene.     

Principles of quantitative absorbance measurements in anisotropic crystals

The accurate measurement of absorbance (A=-log T; T=I/I ₀) in anisotropic materials like crystals is highly important for the determination of the concentration and orientation of the oscillator (absorber) under investigation. The absorbance in isotropic material is linearly dependent on the concentration of the absorber and on the thickness of the sample (A=?·c·t). Measurement of absorbance in anisotropic media is more complicated, but it can be obtained from polarized spectra (i) on three random, but orthogonal sections of a crystal, or (ii) preferably on two orthogonal sections oriented parallel to each of two axes of the indicatrix ellipsoid. To compare among different crystal classes (including cubic symmetry) it is useful to convert measured absorbance values to one common basis (the total absorbance A _tot), wherein all absorbers are corrected as if they were aligned parallel to the E-vector of the incident light. The total absorption coefficient (a _tot=A _tot/t) is calculated by $$\left( {\text{i}} \right)a_{{\text{tot}}} = \sum\limits_{i = 1}^3 {(a_{\max ,i} + a_{\min ,i} )} /2, {\text{or}} {\text{by}} {\text{(ii) }}a_{{\text{tot}}} = a_x + a_y + a_z .$$ Only in special circumstances will unpolarized measurements of absorbance provide data useful for quantitative studies of anisotropic material. The orientation of the absorber with respect to the axes of the indicatrix ellipsoid is calculated according to A _x/A _tot=cos² (x < absorber), and analogously for A _yand A _z. In this way, correct angles are obtained for all cases of symmetry. The extinction ratio of the polarizer (Pe=I _crossed/I _parallel) has considerable influence on the measured amplitude of absorption bands, especially in cases of strong anisotropic absorbance. However, if Pe is known, the true absorbance values can be calculated even with polarizers of low extinction ratio, according to A _max=?log[(T _max,obs?0.5·Pe·T _min,obs)/(1?0.5·Pe)], and similar for A _min. The theoretical approach is confirmed by measurements on calcite and topaz.     

地质样品铜、铁、锌同位素标准物质的研制

合适的标准物质是进行同位素准确分析的基础和关键,本文介绍了基于地质样品的铜、铁、锌同位素分析标准参考物质的研制过程.所研制的标准物质为CAGSR-1,用于该标准物质研制的原始样品为玄武质组分的岩石成分分析国家标准物质GBW07105.按照国家一级标准的要求,对该标准物质进行了严格的均一性、稳定性检验和同位素定值分析.标准物质CAGSR-1的主要特性量值δ65Cu、δ56Fe、δ66Zn的推荐值及95%置信水平的不确定度为:δ65CuSRM976(‰)=0.10±0.02、δ56FeIRMM014(‰)=0.12±0.02、δ66ZnRomil(‰)=7.45±0.01.该标准物质可用于地质与环境样品铜、铁、锌同位素测定中化学流程评价和验证、质谱仪的校正及整个过程的分析质量控制.