Electrical resistivity imaging over natural (in situ) geological samples using physical model studies

To understand the characteristic responses of natural geological samples, viz., black granite, green marble, and graphite sheet, and to have “an a priori” knowledge of their physical property through electrical resistivity imaging, the physical model laboratory setup has been established to conduct scale model studies over targets of finite dimensions and resistivities. The present experiment involves IRIS make SYSCAL Pro-96 measuring system using 48 electrodes with 2-cm interelectrode separation in the laboratory model tank. In the present communication, we have presented the 2D cross section images using Wenner, Wenner–Schlumberger, and dipole–dipole array configurations over the resistive (granite, marble) and conductive (graphite) sheets. In the case of resistive target (black granite sheet, green marble), the combined usage of dipole–dipole and Wenner–Schlumberger arrays provided more accurate measures on target parameters, i.e., the combined usage of both the arrays is preferable in searching high-resistive targets beneath the low-resistive ones over burden. The shape of the resistive target (green marble sheet) is inappropriate when the thickness of the target is greater than one half of the minimum array separation. As the thickness of the target increases, the signatures of the target become feeble, and hence, the shape of the resistive target is not properly reflected in the corresponding tomogram. The response over graphite sheet indicates that the true parameters of the target are not reflected in the cross section, and the existence of the low-resistive (high-conductive) target in the host medium (water) deviates the resistivity of the medium. The target parameters from the cross section using dipole–dipole array are somewhat correlated with true parameters in the case of thin targets at shallow depths. In the case of the sequence of layers of gravel–marble gravel–sand gravel simulated in a small model tank in the physical model laboratory, the thickness of the high-resistive marble layer beneath the low-resistive gravel layer is enhanced conspicuously because of the significant resistivity contrast between gravel and marble.     

基于MC- ICP- MS的地质样品的高精度钾同位素分析方法

近年来,得益于多接收电感耦合等离子体质谱(MC-ICP-MS)的快速发展,钾(K)同位素的分析精度得到显著提升,极大地促进了K同位素地球化学的发展,在示踪大陆风化、壳幔物质循环等方面已经展现出良好的应用前景。目前,样品分离提纯过程繁琐,耗时长,以及ArH⁺对K的直接干扰导致的分析精度不足依旧是K同位素得到更广泛应用的最大阻碍。在使用盐酸、硝酸以及氢氟酸将样品彻底溶解后,利用装有约2.7 mL AG50W-X8(BioRad^TM,200～400目)阳离子交换树脂的定制石英离子交换柱,以及0.5 mol/L硝酸作为淋洗液可以有效地将地质样品中的K与Na、Ti、Mg、Mn、Al、Ca等主要基体元素一次性分离开来,从而有效分离提纯常见地质样品中的K(高Cr样品除外)。在仪器分析方面,为达到最大程度降低测试过程中的ArH⁺产率以及提高仪器测试的稳定状态,分别采用了高分辨模式、高分辨加连续采集模式以及低分辨下扣除ArH⁺干扰模式进行测试,结果表明低分辨模式下测试成本较低,测试稳定时间最长且能达到与高分辨率测试相...     

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％。     

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。     

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.     

Determination of the hydrogen content of synthetic quartz by neutron polarization analysis

Neutron polarization analysis has been used for the quantitative determination of hydrogen in a crystal of synthetic quartz. The observed weighted average value of 1860±950 H/10⁶Si is in good agreement with the value determined from infrared absorption.     

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%。     

电感耦合等离子体发射光谱法在地质样品分析中的应用进展

概述了电感耦合等离子体发射光谱法( ICP?AES)在测定技术方面的进展,强调该仪器测定条件对测定元素曝光强度的影响以及对测定中各元素分析谱线的选择和干扰元素的影响;介绍了ICP?AES测定技术在地质样品分析中的应用。测定土壤、岩石、水洗沉积物、矿石样品、植物样品和水样样品中的元素时,应根据样品性质的不同和测定元素的不同而采用不同的消解体系(酸溶法、碱熔法和微波消解法)。在测定土壤、岩石和水洗沉积物样品时,比较了不同消解体系各自的特点,同时也对比了采用不同消解体系时各元素的方法检出限,结果显示,酸溶法的检出限要明显优于碱熔法;在测定矿石样品时,对比了各元素在不同消解体系中的测定精密度,结果显示测定精密度均较好;总结了测定常见植物样品中无机元素的典型前处理方法以及ICP?AES测定水样中的元素全量和元素不同价态含量的方法。最后,对ICP?AES测定技术在地质行业的应用作了展望,相信ICP?AES还将在地质样品的分析中继续发挥作用。     

电感耦合等离子体质谱法测定地质样品中的碲

本文采用电感耦合等离子体质谱法,对地质样品中的碲的测定进行了研究,建立了一种快速、准确、简便的测定土壤样品中碲的方法。该方法克服了常规方法的局限性。此方法对6个国家标准物质进行了方法验证,12次测定精密度、准确度均符合标准要求。     

电感耦合等离子体质谱法测定砂岩型铀矿样品中分步提取的铀

本文研究地质样品中铀形态的分析方法及应用技术,以进一步说明铀形态分析在地球化学找矿中的重要作用。该方法参考Tessier流程,将样品中的铀分为可交换离子态、碳酸盐结合态、铁锰氧化物结合态、硫化物及有机物结合态和结晶态,分别提取,提取溶液用高分辨率电感耦合等离子体质谱仪进行测量。设计的形态提取配方具有良好的可选择性和可重复性,经过国家标准物质、国际形态标准物质和人工模拟样品验证,证明形态提取试剂配方适合所定义的形态分析。通过对实际样品(总量铀为635μg/g)验证表明,碳酸盐结合态铀提取结果的可重复性最好(RSD为2.6%),其次为硫化物及有机物结合态铀(RSD为4.0%)、结晶态铀(RSD为6.0%)和铁锰氧化物结合态铀(RSD为6.1%),可交换离子态铀提取结果的可重复性最差(RSD为26%)。碳酸盐结合态铀与结晶态铀之比,可以用于反映地下铀矿的存在概率。     

The determination of hydrogen concentration in silicates using ion-beam spectrochemical analysis (IBSCA)

The spectral analysis of radiation emitted from sputtered particles may be used for the quantitative chemical analysis of solids. An important application is the determination of the hydrogen-content of solids via the Balmer H _α line at 656 nm. It is shown that provided an appropriate working curve can be constructed for the calibration of the instrument, IBSCA can be used for the determination of the bulk hydrogen-content in quartz and other silicates.     

氢化物发生原子荧光光度法测定地质样品中的痕量锗

实验选择了最佳仪器工作条件,比较了不同载流酸对荧光强度的影响,用L-半胱氨酸-硫脲-酒石酸混合溶液消除干扰.本法检出限0.08μg/g(n=12),8个土壤标样的RSD为4.8%～9.6%(n=12),ΔtgC为0.002～0.015,此法可满足化探分析的要求.     

Determination of total selenium in geological samples by HG-AFS after concentration with thiol cotton fiber

Standard reference material and different geological samples were dissolved by system A （the mixture of nitric and perchloric acids） and system B （mixture of nitric, perchloric and hydrofluoric acids）, and total Se in all samples was measured by hydride-generation atomic fluorescence spectrometry （HG-AFS） after concentration with thiol cotton fiber （TCF）. The analytical results obtained by the two digestion method are in good agreement （within the limit of errors） for most of the samples, particularly for those having recommended values. The Se concentrations determined by the two methods are of no difference, and the correlation coefficient is 0.9986; the relative standard deviation （RSD） for the determination of 0.04 μg/g Se is 10.2%. The recovery rates of systems A and B by the standard-addition method were 96%-106% and 99%-104%, respectively.     

A nuclear method for the analysis of light elements (Z </ 11) in geological samples

A nuclear method of measurement of major as well as trace light elements in silicates is presented. This method is particularly applied to the determination of Li content in micas in order to optimize some experimental conditions. The other elements that can be reached with a good sensitivity ( 10 ppm) are Be, B, F and Na. The particles which provoke the nuclear reactions are single-charged -particles provided by a Van de Graaf accelerator. The possibility of obtaining a well-focused -beam and the good accuracy of the method permit us to consider this method as a valuable complement of the electron microprobe.     

The automated photometric determination of vanadium in geological samples with 4-(2-pyridylazo) resorcinol

Vanadium is determined in geological samples utilising the red complex formed between V⁵⁺ and 4-(2-pyridylazo) resorcinol. The determination is performed with the Technicon Auto Analyzer. The method has been applied to the determination of the element in standard rock and mineral samples after fusion with sodium carbonate and magnesium oxide. Using this sensitive method, it is possible to determine as little as 1 p.p.m. vanadium in a 200-mg sample of silicate rock or mineral.     

PAN-S螯合形成树脂分离富集极谱连测地质样品中贵金属

采用L-（2-吡啶偶氮）-2-萘酚-15-磺酸（PAN-S）作为螯合剂制备螯合形成树脂。研究了该树脂的性能及各种条件对分离富集和测定的影响。用pH1．5的盐酸溶液做淋洗剂，柱高为20cm，过柱流速为0．30mL·min^-1，pH1．0的3％的硫脲-盐酸60mL洗脱时，贵金属元素能与常见的金属离子分离，并定量富集于树脂上，用极谱法进行测定标准回收实验。贵金属元素的回收率为96％～104％。     

XRF Determination of 17 Trace Elements in Geological Samples Using an Extended Compton Scattering Correction Procedure

This work is intended to explore a fast and effective apoproach to the determination of various trace elements in geological samples throuth improvement and simplification of the method developed by Reynolds (1963,1967),Absorption correction was made for the Fe content to eliminate the effect caused by inconsistency in mass absorption coefficients among the samples.A computer-aid regression analysis was performed on a number of standards of various compositions,which resulted in a set of calibration equations for directly converting X-ray intensities to concentrations.An analytical error of 10-30% was involved in the analyses of most elements.     

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%.     

Sketching the temperature history of geological samples: analyses of diffusion profiles using multilayer perceptrons

A method using multilayer perceptrons for analysing diffusion profiles and sketching the temperature history of geological samples is explored. Users of this method can intuitively test and compare results thinking in terms of analytical solutions of the diffusion equation whilst the bulk of the work is made computationally. Being neither completely analytical nor numerical, the method is a hybrid and represents an ideal man-machine interaction. The approach presented in this paper should be preferred when the retrieval of the diffusion coefficients from concentration profiles using dimensionless parameters is not possible and/or there is more than one unknown parameter in the analytical solution of the diffusion equation. Its versatility is a key factor for extending the potential of Dodson’s formulation. The case of a species produced by a radiogenic source and diffusing in a cooling system is therefore discussed. Both the classical change of variable for diffusion coefficients depending on time and an alternative approach decomposing the overall effect of diffusion into a sum of effects due to smaller events could be used to tackle this problem. As multilayer perceptrons can approximate any function, none of the assumptions originally stated by Dodson are necessary.     

Accounting for spatial patterns of multiple geological data sets in geological thematic mapping using GIS-based spatial analysis

This paper presents a Geographic Information System (GIS)-based spatial analysis scheme to account for spatial patterns and association in geological thematic mapping with multiple geological data sets. The multi-buffer zone analysis, the main part of the present study, was addressed to reveal the spatial pattern around geological source primitives and statistical analysis based on a contingency table was performed to extract information for the assessment of an integrated layer. Mineral potential mapping using multiple geological data sets from Ogdong in Korea was carried out to illustrate application of this methodology. The results obtained from the case study indicated that some geochemical elements and residual magnetic anomaly dominantly affected spatial patterns of the mineral potential map in the study area and the dominant classes of input data layers were also extracted. This information on spatial patterns of multiple geological data sets around mines could be used as effective evidences for the interpretation of the integrated layer within GIS.