Improved stepwise solvent extraction scheme for geochemical trace analysis using flame atomic absorption

A solvent extraction, flame atomic absorption analytical scheme is reported for the elements Au, Tl, Sb, Ga, Mo, Cu, Ni, Co, Ag, Bi, Cd, Pb, Zn and Mn in geological materials. Results are quoted for NIM standard rocks and for USGS reference samples, and are compared with published values; practical detection limits are generally better than 0.2 ppm. A stepwise solvent extraction and preconcentration process is utilised (chloro complexes, diethyldithiocarbamate and 8-hydroxyquinoline chelates are used with methyl isobutyl ketone and $\text{n-}\text{butyl}$ acetate as solvents) which allows the reproducible isolation of groups of elements which generally occur at similar concentrations geologically. Analytical accuracy is maintained by the chemical elimination, within each step, of other chelate-forming elements present at higher concentrations which would cause spectral interferences during the atomic absorption measurements. The complete stepwise process is reported together with elemental partition data which covers a range of aqueous ionic conditions.     

石墨炉原子吸收法测定化探样品中的痕量金

试样经灼烧、王水(1 1)分解后,置于10%±的王水介质中经泡塑富集,高温灰化,小体积王水浸取后,以N i作为A u的稳定改进剂,用石墨炉原子吸收法测定A u。本方法检出限为0.18ng/mL,相对标准偏差为3.98%~6.12%。适用于地质、化探样品中痕量金的测定。     

石墨炉原子吸收光谱法测定化探样品中微量金的方法研究

用聚醚型聚胺酯泡沫塑料吸附金,在王水中加入适量的FeCl3可大大提高泡沫塑料对金的吸附能力。然后用Z-2700石墨炉原子吸收光谱法测定金,经检验样品的精密度、准确度大大提高,完全满足化验要求。     

A spatial analysis method for geochemical anomaly separation

One purpose of using statistical methods in exploration geochemistry is to assist exploration geologists in separating anomalies from background. This always involves two types of negatively associated errors of misclassification: type I errors occur when samples with background levels are rejected as background; and type II errors occur when samples with anomalous values are accepted as background. A new spatial statistical approach is proposed to minimize errors of total misclassification using a moving average technique with variable window radius. This method has been applied for geochemical anomaly enhancement and recognition as demonstrated by a case study of Au and Au-associated data for 698 stream sediment samples in the Iskut River area, northwestern British Columbia. Similar results were obtained using the fractal concentration-area method on the same data. By employing spatial information in the analysis, the process of selecting anomalies becomes less subjective than in more traditional approaches.     

A statistical analysis of exploration geochemical data for uranium

This paper describes a statistical analysis of reconnaissance exploration geochemical data for uranium. Three sets of data were analyzed, as they related to: (a) Charlotte-Winston-Salem and (b) Charlotte two-degree NTMS quadrangles of the south-eastern U.S.A. The coefficient of variation for uranium in each of the three sets of data was less than unity and hence no transformation of the original variable was needed. These data were subjected to correlogram analysis. A first-order Markovian model of the type: Y₀ exp (-a |p|) was fit by the least-squares method to serial correlation coefficients of these data using the method proposed by Deming (1948). The model was tested by computing the variance-volume relationship for assumed individual blocks of unit length. The noise in the input (record) was eliminated by the application of an optimum bilateral exponential smoothing technique developed by Agterberg. A comparison of spectral density estimates obtained by a maximum entropy method employing Yule-Walker equations and the Burg algorithm was also made. The prediction error coefficients needed to determine the order of the autoregressive process and hence the spectral densities were determined in both cases for the three sets of data.On leave from National Geophysical Research Institute, Hyderabad-7, India.     

区域地球化学样品分析质量控制系统关键模块的实现方法

为满足各种区域地球化学调查(包括1∶5万、1∶20万和多目标地球化学等) 对数据质量控制的要求, 并提高工作效率, 研制开发了区域地球化学样品分析质量控制系统。由于该系统具有极强的专业性并采用C /S和B /S双结构结合的开发模式, 因此一些关键模块的实现至关重要, 其中包括数据库关键表的设计、任务单的下载、分析结果的上传、质量控制样品的插入和数据质量的实时监控等。本文详细介绍了这些关键模块的实现方法, 并给出若干模块的具体实现代码。     

A procedure for partitioning bulk sediments into distinct grain-size fractions for geochemical analysis

A method to separate sediments into discrete size fractions for geochemical analysis has been tested. The procedures were chosen to minimize the destruction or formation of aggregates and involved gentle sieving and settling of wet samples. Freeze-drying and sonication pretreatments, known to influence aggregates, were used for comparison. Freeze-drying was found to increase the silt/clay ratio by an average of 180 percent compared to analysis of a wet sample that had been wet sieved only. Sonication of a wet sample decreased the silt/clay ratio by 51 percent. The concentrations of metals and organic carbon in the separated fractions changed depending on the pretreatment procedures in a manner consistent with the hypothesis that aggregates consist of fine-grained organic- and metal-rich particles. The coarse silt fraction of a freeze-dried sample contained 20–44 percent higher concentrations of Zn, Cu, and organic carbon than the coarse silt fraction of the wet sample. Sonication resulted in concentrations of these analytes that were 18–33 percent lower in the coarse silt fraction than found in the wet sample. Sonication increased the concentration of lead in the clay fraction by an average of 40 percent compared to an unsonicated sample. Understanding the magnitude of change caused by different analysis protocols is an aid in designing future studies that seek to interpret the spatial distribution of contaminated sediments and their transport mechanisms.     

MATPLOT:一款基于MATLAB的地球化学数据分析成图软件

地球化学数据统计分析图解是目前岩石地球化学研究工作中常用的手段。目前常用的软件或多或少都存在一些不足之处。本文提出的MATPLOT是一款应用MATLAB编写而成的地球化学数据成图软件,可以在Windows/Mac OS/Linux多种操作系统平台中运行。与现有常用软件相比,该软件更具优势：可以更方便地实现较大地球化学数据量的导入,无需对数据进行繁琐的格式整理;更便捷地对数据进行二元散点图、三角图、标准化折线图、柱状图、概率密度图和同位素演化图等6种常用图解类型的成图,以及对数据图的展示内容和效果进行各种调整。此外,MATPLOT还可以对数据进行多种平均值计算（普通平均值、图基双权加权平均值和误差相关加权平均值）和相关性分析。

     

深部矿产资源立体地球化学勘查方法技术体系

深部矿产资源的勘查是战略性矿产资源勘查的一个重要方面。找矿实践证明，化探方法技术在矿产勘查乃至深部找矿中发挥了重要的、不可或缺的作用。找矿工作的不断深入和找矿难度的不断加大，促使化探方法技术不断的发展和完善，在传统方法技术的基础上，研发出了许多新的方法技术。本文从方法论和系统论的角度出发，对现有的找寻深部隐伏矿盲矿的有效化探方法技术进行了系统的归纳和总结，提出了立体地球化学勘查方法技术体系的概念，将立体地球化学勘查方法技术划分为地面地球化学测量方法技术和地下地球化学测量方法技术，建立了深部矿产资源立体地球化学勘查方法技术体系。不同的方法技术有不同的优势和不同的适用条件，实际工作中应当根据不同的勘查阶段，不同的勘查目的和不同的地质地球化学条件选择不同的立体方法技术组合才能发挥出最大效益，取得最大效果。     

Scoresum — A technique for displaying and evaluating multi-element geochemical information, with examples of its use in regional mineral assessment programs

A technique called SCORESUM was developed to display a maximum of multi-element geochemical information on a minimum number of maps for mineral assessment purposes. The technique can be done manually for a small analytical data set or can be done with a computer for a large data set. SCORESUM can be used with highly censored data and can also weight samples so as to minimize the chemical differences of diverse lithologies in different parts of a given study area.The full range of reported analyses for each element of interest in a data set is divided into four categories. Anomaly scores — values of O (background), 1 (weakly anomalous), 2 (moderately anomalous), and 3 (strongly anomalous) — are substituted for all of the analyses falling into each of the four categories. A group of elements based on known or suspected association in altered or mineralized areas is selected for study and the anomaly scores for these elements are summed for each sample site and then plotted on a map. Some of the results of geochemical studies conducted for mineral assessments in two areas are briefly described. The first area, the Mokelumne Wilderness and vicinity, is a relatively small and geologically simple one. The second, the Walker Lake 1° × 2° quadrangle, is a large area that has extremely complex geology and that contains a number of different mineral deposit environments. These two studies provide examples of how the SCORESUM technique has been used (1) to enhance relatively small but anomalous areas and (2) to delineate and rank areas containing geochemical signatures for specific suites of elements related to certain types of alteration or mineralization.     

A spherical electron-channelling pattern map for use in quartz petrofabric analysis

Electron channelling patterns (ECP's) are formed in the scanning electron microscope (SEM) by the interaction between the incident electrons and the lattice of crystalline specimens. The patterns are unique for a particular crystallographic orientation and are therefore of considerable potential in petrofabric studies provided they can be accurately indexed. Indexing requires an ECP-map of the crystallographic stereogram or unit triangle covering all possible orientations and hence ECP patterns. Due to the presence of long-range distortions in planar ECP-maps, it is more convenient to construct the maps over a spherical surface. This also facilitates the indexing of individual ECP's. A spherical ECP-map for quartz is presented together with an example of its use in petrofabric analysis.     

A trace-element geochemical model for imperfect fractional crystallization associated with the development of crystal zoning

Although many petrological studies of volcanic rocks have suggested that crystallization proceeds within magma bodies, highly compatible trace elements do not display the marked variations and extreme depletions predicted to result from perfect fractional crystallization. Imperfect crystal-liquid separation is a key process in explaining this paradox. The presence of suspended crystals greatly affects variations in highly compatible elements, and has been quantitatively modeled by assuming perfect equilibrium between the suspended crystals and the liquid (equilibrium crystallization and imperfect separation; ECIS); however, volcanic rocks generally contain zoned phenocrysts that reflect the absence of solid-state equilibration. The present study develops a mass-balance model for zoned crystallization and imperfect separation (ZCIS). The ZCIS process is more efficient than the conventional ECIS process in generating depleted compatible elements. These two end-member models are able to explain the compositional range of igneous rocks that experienced imperfect fractional crystallization under natural conditions. The predicted compositional regions in bivariate trace-element diagrams successfully account for the sizes and shapes of the regions defined by whole-rock and melt-inclusion data from the Bishop Tuff, CA, USA.     

Integrating multivariate statistical analysis with GIS for geochemical assessment of groundwater quality in Shiwaliks of Punjab,India

The dependency of people on groundwater has increased in the past few decades due to tremendous increase in crop production, population and industrialization. Groundwater is the main source of irrigation in Shiwaliks of Punjab. In the present study the samples were collected from predetermined location as was located on satellite image on basis of spectral reflectance. Global positioning system was used to collect samples from specific locations. Principal components analysis (PCA) together with other factor analysis procedures consolidate a large number of observed variables into a smaller number of factors that can be more readily interpreted. In the present study, concentrations of different constituents were correlated based on underlying physical and chemical processes such as dissociation, ion exchange, weathering or carbonate equilibrium reactions. The PCA produced six significant components that explained 78% of the cumulative variance. The concentration of the few trace metals was found to be much higher indicating recharge due to precipitation as main transport mechanism of transport of heavy metals in groundwater which is also confirmed by PCA. Piper and other graphical methods were used to identify geochemical facies of groundwater samples and geochemical processes occurring in study area. The water in the study area has temporary hardness and is mainly of Ca–Mg–HCO₃ type.     

A new rating system approach for risk analysis of rock slopes

In this paper, an approach is presented to analyze the stability risk of rock slopes based on a new rating system. Three factors are used to estimate the risk level of rock slopes: (1) failure probability, (2) element at risk rating, and (3) vulnerability rating. Element at risk and vulnerability ratings are both given a range from 0 to 10, and the probability of failure is varied between 0 and 1, so the risk rating ranges between 0 and 100. This risk rating can be used to determine both the quantitative and qualitative risk levels of slopes at the same time. The method is tested on the western sector of the slopes facing Songun copper plant phase III, Iran, to clarify its procedures and assess its validity. Deterministic kinematic analyses showed that the slope has a potential for circular failure. Risk assessments revealed that the risk levels of the slope in both static and pseudo-static conditions are “very low” and “high,” respectively.

     

A new rating system approach for risk analysis of rock slopes

In this paper, an approach is presented to analyze the stability risk of rock slopes based on a new rating system. Three factors are used to estimate the risk level of rock slopes: (1) failure probability, (2) element at risk rating, and (3) vulnerability rating. Element at risk and vulnerability ratings are both given a range from 0 to 10, and the probability of failure is varied between 0 and 1, so the risk rating ranges between 0 and 100. This risk rating can be used to determine both the quantitative and qualitative risk levels of slopes at the same time. The method is tested on the western sector of the slopes facing Songun copper plant phase III, Iran, to clarify its procedures and assess its validity. Deterministic kinematic analyses showed that the slope has a potential for circular failure. Risk assessments revealed that the risk levels of the slope in both static and pseudo-static conditions are “very low” and “high,” respectively.     

一种新的适合富有机质沉积岩的Re-Os同位素分析方法初探

虽然富有机质沉积岩中的Re和Os主要都富集在有机质中,但其中碎屑部分中的Re和Os也会影响其Re-Os等时线的准确度和精度。目前最常用的Cr O3-H2SO4溶样法虽然能尽量避免碎屑物质中Re和Os的溶出,但该方法具有Re流程空白高和环境污染严重等问题。因此,本研究尝试在富有机质沉积岩Re-Os同位素分析中使用H2O2-HNO3溶样来代替Cr O3-H2SO4溶样。本研究利用国际油页岩标样SGR-1b(USGS)为实验研究对象,分别对HCl-HNO3溶样、Cr O3-H2SO4溶样和H2O2-HNO3溶样3种溶样方法进行了对比研究。研究表明,H2O2与HNO3的体积比约为5﹕1的H2O2-HNO3溶液,不仅能保证样品和稀释剂的Re、Os同位素达到同位素交换平衡而且尽可能地避免碎屑物质中Re和Os的溶出。本方法相比于HCl-HNO3溶样,能尽量避免碎屑物质中Re和Os的溶出;而相比于Cr O3-H2SO4溶样,该方法具有本底低、无污染的优点。最后利用H2O2-HNO3溶样方法对广西金秀地区的泥岩样品和广东大宝山地区的碳质页岩样品进行了Re-Os同位素定年分析,分别得到了(404±5)Ma(IOs=1.57±0.13,n=8,MSWD=50)和(211±11)Ma(IOs=0.67±0.09,n=5,MSWD=11.1)的等时线年龄,这一结果与HCl-HNO3溶样得到的结果((412±11)Ma,IOs=1.18±0.38,n=8,MSWD=311;(223±18)Ma,IOs=0.59±0.14,n=5,MSWD=63)在误差范围内一致,但更为精确。     

利用地球化学资料评价水淹层方法研究:以大庆杏南油田为例

通过对水淹层地球化学资料的分析,总结出了不同程度水淹层的地球化学特征,提出了利用地球化学资料从定性识别到定量评价的水淹层评价思路,建立了水淹层水淹程度定性识别方法、剩余油饱和度和含水率定量评价模型.对储层物理性质、岩性、流体性质、水淹程度不同的108口井529层水淹层进行了评价,剩余油饱和度与经校正后的密闭取芯井岩芯分析剩余油饱和度非常接近,水淹级别、含水率与单层试油结果一致.证明利用地球化学资料评价水淹层方法是可行的,结果是可靠的,该方法有很好的推广应用前景.     

A simplified analysis approach for the effect of the installation of adjacent XCC pile on the existing single XCC pile in undrained clay

Acta Geotechnica - In this paper, a simplified two-stage analysis method is introduced to predict the lateral response of the existing X-section Cast-in-place Concrete (XCC) pile caused by adjacent...     

稳定同位素和微量元素在多源多汇体系中地球化学行为的理论模拟

根据地质体系多源多汇的特点,引进了一种新的定量地球化学理论模型,适用于模拟稳定同位素和微量元素在具有多个物质来源和多种分馏途径的地质体系中的变化规律。运用本文多源多汇模型研究岩浆同化-分异结晶过程中微量元素和稳定同位素的行为,所得的结果与前人AFC模型结果一致。运用此多源多汇模型对岩浆水与大气水混合过程中结晶出的石英进行模拟计算,发现其氧同位素组成随着结晶温度的降低而变大。大气中甲烷的产生和消耗有多种途径,是一种多源多汇体系,运用此模型研究它的碳同位素组成,发现其值随着甲烷总量的增多而变大。多源多汇模型不仅从更高的层次上包含了简单分馏模式、多元混合模式和AFC模式,而且可以研究这些模式不能解决的复杂地球化学过程。