Trace element zoning in pyrite determined by PIXE elemental mapping: evidence for varying ore–fluid composition and electrochemical precipitation of gold at the Spitskop deposit,Saldania Belt,South Africa

The geochemistry of pyrite associated with mesothermal ‘invisible’ gold mineralization in the Neoproterozoic Saldania Belt was studied with micro‐PIXE. The petrologically observed weak zoning of pyrite was clearly visible on elemental maps generated by this analytical method. It also allowed the positive identification of two generations of pyrite. Early, irregular pre‐ to syn‐tectonic grains are As‐poor and display strongly zoned later, possibly post‐tectonic, overgrowths rich in As, Ni, Sb and Pb. This late phase also produced a generation of individual, distinctly zoned euhedral grains of similar composition. Gold is extremely fine‐grained and hosted by the zoned pyrite grains as submicroscopic specks located on the boundary between As‐poor and As‐rich bands. This association is indicative of the electrochemical precipitation of gold. Zoning of the elements Ni, Sb and Pb in the late‐stage pyrite is attributed to selective precipitation in response to changes in composition and physico‐chemical conditions of the mineralizing fluids that have been derived from devolatilization of the enclosing metamorphosed volcano‐sedimentary pile. Copyright © 2004 John Wiley & Sons, Ltd.     

Comparison of trace elements analysis of nephrite samples from different deposits by PIXE and ICP‐AES

Comparing values of trace elements determined by external‐beam proton‐induced X‐ray emission (PIXE) and inductively coupled plasma atomic emission spectrometry (ICP‐AES) is important to find the provenience of raw materials of ancient nephrite artifacts, because most previous elemental characterizations of nephrite minerals were obtained by ICP‐AES, but PIXE presents the possibility of nondestructive analysis for largely and integrally ancient nephrite artifacts. In this work based on 12 nephrite minerals, it shows that the distribution of trace elements of nephrite samples both in PIXE and ICP‐AES data are generally consistent, although large differences exist in some elements. According to the trace elements, the two types of nephrite mineralization origins can be distinguished, determined by PIXE and ICP‐AES, respectively. Moreover, depending on the PIXE and ICP‐AES data, Sr can be regarded as fingerprint element of Xiaomeiling nephrite minerals, and the differentiation of Sr content between Xiaomeiling nephrite minerals and ancient nephrite artifacts from Liangzhu culture (3300–2300 bc ) is clear evidence that the raw materials of the artifacts are not from Xiaomeiling deposit. The nephrite minerals from Wenchuan deposit can be distinguished from other samples because of their high values of Mn/Fe. Therefore, the PIXE can be used with ICP‐AES to judge mineralization mechanism and find fingerprint elements of raw materials of ancient nephrite artifacts. Copyright © 2012 John Wiley & Sons, Ltd.     

LA-ICP-MS analysis of platinum-group elements and other elements of interest in ancient gold

One of the most promising methods for ancient gold analysis is laser ablation–inductively coupled plasma mass spectrometry (LA-ICP-MS). It is a quasi-non-destructive multi-elemental analytical method with detection limits in the range of ppm or below, depending on the element. Internal and external standardizations are used. Different types of standards are necessary to measure major (required for the internal standardization), minor and trace elements. High-purity gold standards doped with trace elements as well as ancient gold coins were found suitable for that purpose. The reproducibility and the accuracy of the results obtained are good enough to consider LA-ICP-MS as reliable to determine trace-element concentrations in ancient gold. PACS 81.70; 82.80     

利用PIXE和ICP-AES 对蛇纹石原料及中国古代蛇纹石玉器的微量元素分析

以蛇纹石这一中国传统的玉材为对象,旨在通过微量元素含量分析来探索古代蛇纹石玉器原料的可能来源。采用无损的外束质子激发X射线荧光技术(PIXE)对来自中国几个典型矿区的蛇纹石样品主量元素和微量元素进行了分析。同时也采用有损的电感耦合等离子体原子发射光谱技术(ICP-AES)对这些蛇纹石样品的微量元素含量进行了比较分析。结果表明,两种分析方法所获取的蛇纹石微量元素含量趋势具有一致性,说明PIXE无损分析技术可以应用于蛇纹石的微量元素分析研究。讨论了蛇纹石的微量元素含量与地质成因之间的关系,这些蛇纹石的微量元素含量存在明显的差异,这种差异可以用来区分不同地质成因的蛇纹石。Ⅰ型地质成因的蛇纹石中微量元素中Ni含量较低,且几乎不含Cr和Co,而Ⅱ型地质成因的蛇纹石中则含有较高微量元素的Cr,Co和Ni。采用PIXE技术分析了来自浙江、江苏、河南、安徽和湖北等省出土的新石器时代至战国时期(4585 BC—221 BC)14个遗址或墓葬出土的18件蛇纹石玉器的化学成分,通过与两种地质成因类型蛇纹石的微量元素比较分析,初步推测了这些蛇纹石玉器原料的可能来源。以蛇纹石微量元素含量与地质成因类型之间的关系来探索古代蛇纹石玉器玉料可能的来源是一种有益的尝试。     

现代仪器在泌尿系结石元素分析中的运用

对泌尿系结石所含元素进行准确的分析可为治疗尿石症和预防其复发提供重要的参考,文章综述了现代仪器分析技术在泌尿系结石元素分析中的运用及其研究进展,这些技术包括：X射线光电子能谱(XPS)、质子激发X射线发射光谱(PIXE)、能量分散X射线分析(EDX)、电子束探针微区分析(EPMA)、原子发射光谱(AES)、原子吸收光谱(AAS)、电感耦合高频等离子体发射光谱(ICP)、X射线荧光光谱(XRF)及离子选择性电极等。     

Über Anwendungsmöglichkeiten der PIXE-Methode in der Luftstaubanalytik

Application of PIXE to the Element-Analysis of Airborne Dust The method of particle-induced X-ray emission (PIXE) is used in various fields of trace element analysis. Because of the small sample masses needed for PIXE it is shown, that this method in combination with time sequential sampling is able to measure short-term variations of trace element concentrations in the air.     

Application of PIXE for the determination of transition elements in the grouping study of archaeological clay potteries

Trace element concentrations play an important role in grouping and provenance studies of archaeological artifacts. Particle‐inducedX‐ray emission (PIXE) using low energy proton beams (1.5 and 3 MeV) from a tandem particle accelerator was used to analyze the ancient clay potteries collected from an ancient Buddhist site in India. Concentrations of 13 elements, including eight transition elements, were determined. The concentrations of transition elements were used for the grouping study by statistical cluster analysis according to the similar and dissimilar elemental distribution within the samples. Two International Atomic Energy Agency Reference Materials (RMs) were analyzed to validate the PIXE method. Two samples were analyzed by both PIXE and instrumental neutron activation analysis (INAA) as a part of quality assurance. Grouping results were used for preliminary provenance study. Copyright © 2017 John Wiley & Sons, Ltd.     

Quantitative determination of mineral phase effects observed in APXS analyses of geochemical reference materials

Calibration of the Curiosity Rover's alpha particle X‐ray spectrometer (APXS) was accomplished using geochemical reference materials and a fundamental parameters treatment of the X‐ray fluorescence and particle‐induced X‐ray emission (PIXE) excitation processes. For most major and minor elements the influence of different rock types was not significant. For the three light elements, Na, Mg, and Al, which are excited almost entirely by PIXE, systematic differences among felsic and mafic rocks were observed. A qualitative explanation is found in the very shallow interrogation depth (a few microns), which suggests that the X‐rays of these elements must emerge from a single mineral rather than an assumed average over the various minerals present. A quantitative explanation was sought by determining the mineralogy of several reference materials and computing their expected PIXE X‐ray yields with an adaptation of the yield prediction sub‐routine GUYLS in the Guelph PIXE software package GUPIX. The complexity of assigning the certified overall element mass fractions to specific minerals limited this exercise to cases with only a few minerals present. Good agreement was found between the X‐ray yields determined in the calibration exercise and those predicted in this new approach. It is expected that automation of the computational approach may enable examination of mineralogically more complex reference materials. This might also offer a means of coupling results from the X‐ray diffraction and APXS instruments on Mars. Copyright © 2014 John Wiley & Sons, Ltd.     

Studies on the composition of ancient Indian punch‐marked silver coins

Punch‐marked coins are the oldest known numismatic objects used in ancient India. Seven punch‐marked silver coins were analysed by using the non‐destructive multi‐elemental PIXE technique. A 3 MeV proton beam from a pelletron accelerator was used for irradiation of these samples to obtain the spectral data and GUPIX software was employed to derive the elemental concentrations. The results reveals that silver, copper, gold and lead are significant constituents of the punch‐marked silver coins and there are also traces of elements such as Ti, Cr, Mn, Fe, Co, Ni, As and Y, which seems to imply that PIXE can be used effectively for the non‐destructive quantitative analysis of ancient coins. Copyright © 2004 John Wiley & Sons, Ltd.     

Multivariate analysis applied to particle‐induced X‐ray emission mapping

The use of particle‐induced X‐ray emission (PIXE) for elemental speciation and quantification has gained new attention thanks to mapping capabilities. Microprobes are able to raster a proton beam and produce elemental maps on the micrometre scale. Moreover, recent developments of in‐air PIXE instrumentation have enabled the acquisition of large area elemental maps. However, the amount of data produced is very large, and the data processing is not trivial. In this paper, we propose the use of multivariate analysis to process data of PIXE mapping. First, we apply the non‐negative matrix factorization (NMF), which is a nonsupervised machine‐learning algorithm, to decompose the data into a smaller number of components; then, we use the k‐means algorithm to divide the pixels into categories regarding similarities in the NMF results; finally, we sum the spectra of all pixels in the same category so that the results can be analyzed by standard procedures for PIXE quantification. This last step is important to enable the quantification of the elements found in each component by correctly accounting for matrix self‐absorptions. With the procedure described in this paper, not just, we reduced the number of variables, facilitating the reasoning process on the data by employing the multivariate analysis, but we also increased the counting statistics by summing similar pixels leading to better results concerning the quantification of trace elements. We also propose methods for both, the automatic determination of the optimal number of components to describe the dataset, and for the combined analysis of multiple detectors.     

Fish otolith trace element maps: new approaches with synchrotron microbeam x‐ray fluorescence

Otoliths, the carbonate earstones of fishes, take up minor and trace amounts of elements as they accrete through a fish's life. We apply synchrotron microbeam x‐ray fluorescence methods to establish a breakthrough in high‐resolution, simultaneous area mapping of multiple trace elements in otoliths, with spatial resolution down to 20 µm and trace element detection down into the part per million range for multiple elements. Concentration maps of Ca, Sr, Zn and, for the first time, Ba, Mn, and Se are obtained simultaneously. Combinations of these elemental maps provide new insights into the environmental history of fishes and their lifetime movements, illustrated by several case studies. This method helps pave the way toward improved spatial analysis of otolith microchemistry. Copyright © 2007 John Wiley & Sons, Ltd.     

Micro‐PIXE studies of low‐level gold solubility in natural magmas: Experiments on two felsic magmas

The limits of gold solubility in granitic magmas are poorly constrained, yet may be important for understanding the formation of several gold deposit types. This is largely due to the fact that this parameter cannot be readily measured in natural rocks. Experimental approaches are also difficult, as an analytical technique is required that combines a high level of spatial resolution (typically <5 µm) with the capability to measure gold in low concentrations. In an attempt to address this problem, experiments were conducted to investigate gold solubility in sulphur‐ and chlorine‐bearing granitic and syenitic magmas, and the products were analysed by micro‐PIXE (particle‐induced x‐ray emission). Starting glasses were synthesized from aluminosilicate gels fired at 1000°C, and were sealed within gold capsules, with 4.4 wt% H₂O and variable proportions of either chlorine or sulphur as potential gold complexing agents. The initially gold free glasses were equilibrated with the pure gold capsules at conditions of 1.5 MPa, 750°C and at fO₂≈NNO buffer, for a period of at least 150 h. All experiments produced quenched granitic and syenitic glasses containing a disseminated, high‐temperature silicate mineral assemblage, in addition to oxide and/or sulphide and small gold crystals. The gold, sulphur and chlorine concentrations of the glasses were analysed, and under the specific analytical conditions used in this study micro‐PIXE was able to detect gold in the glasses at levels as low as 2 ppm. The PIXE data demonstrate that, under the conditions used in this investigation, sulphur is a more effective complexing ligand than chlorine for incorporating gold into the melt structures, and that surprisingly high gold concentrations of up to 4400 ppm were attained in the syenitic magma with 1 wt% sulphur added. Thus, micro‐PIXE analysis has been shown to be capable of constraining the concentration of gold at the generally low values encountered in solubility studies on felsic natural magma compositions, thereby laying the groundwork for future research in this field using the PIXE technique. Copyright © 2004 John Wiley & Sons, Ltd.     

Combined PIXE and X‐ray diffraction analysis of accretionary lapilli from the Cretaceous/Paleogene boundary El Guayal Section,Tabasco, Mexico

By employing the techniques, X‐ray powder diffraction (XRPD) and particle‐induced X‐ray emission (PIXE), it could be obtained in a simply way an overall vision of the structure and chemical composition of a spheroid (lapillus) collected in the K/Pg deposit located at the place called El Guayal in Tabasco, Mexico. The XRPD analysis indicates the presence of an amorphous and four crystalline phases (quartz, calcite, ankerite, and montmorillonite) in the spheroid. None sulfur crystalline phases were detected. PIXE results show the presence of different atoms in a weight percentage that follows the sequence: Si > Al > Ca > Fe > Sr > Cu > Ti > Mn > Y > Rb > Zn > Pb. None of platinum group elements were detected. PIXE analysis by of the lapillus shows the presence of the most abundant atoms in the Earth's crust, but in this case, the relative abundance Fe‐Ca is inverted, and the Sr/Rb proportion is considerably higher than that observed in the crust. Additionally, nor sulfur or any of the platinum group elements was detected in the lapillus. Except for the case of trace elements detected, in general, no characteristic pattern is observed in the distribution of the most abundant elements. Copyright © 2015 John Wiley & Sons, Ltd.     

Determination of Pb,Zr, Ti,Sr, Cr,Nb and La in lead zirconate titanate ceramics by particle‐induced X‐ray emission

A particle‐induced X‐ray emission (PIXE) technique has been used in the determination of the principal components Pb, Zr and Ti and the substituting elements Sr, Cr, Nb and La in lead zirconate titanate ceramics. In general, precision of analysis was concentration dependent from each element under study. For Pb, precision varied between 0.13% and 0.16%, at higher concentration of 59.32–64.5%. It was around 6–9% for Sr, Cr and Nb at concentrations of 1% or lower. Particular attention was devoted to the estimation of the analysis trueness. With this purpose, three methods were applied: (1) comparison of PIXE and inductively coupled plasma optical emission spectrometry concentrations, (2) recovery study and (3) comparison with a laboratory standard. Trueness of analysis was around 100 ± 10% for the evaluated elements Pb, Zr, Ti, Sr and Cr. The expected stoichiometry and elemental composition homogeneity of a wide group of produced ceramics were confirmed by the PIXE technique. Copyright © 2012 John Wiley & Sons, Ltd.     

豫西陆院沟金矿黄铁矿拉曼光谱特征及其对多期成矿的指示意义

豫西陆院沟金矿是熊耳山地区重要的破碎蚀变岩型金矿，黄铁矿是其主要的载金矿物，对黄铁矿主量元素、微量元素、同位素等进行测试能够分析金矿的成矿过程，常规的测试手段主要有电子探针、激光剥蚀电感耦合等离子质谱等方法，但这些方法具有测试时间长、成本高的缺点。不同温压条件下形成的黄铁矿其光谱特征不同，对黄铁矿进行激光拉曼测试，分析其拉曼特征位移峰及半高宽（FWHM）的变化可判断黄铁矿形成的温度和压力，进一步可推测金矿的成矿过程，该方法相比于传统的分析测试方法具有经济、高效的优势。通过对陆院沟金矿不同标高430~670 m的黄铁矿样品进行拉曼光谱分析发现其379 cm-1附近的特征拉曼位移A_g自标高430~500 m呈现不断增大的趋势，自标高500~580 m呈现不断减小的趋势，自标高580~670 m又呈现不断增大的趋势。A_g拉曼位移一般随着成矿压力的增大而增大，推断控矿断裂存在两期构造活动，第一期构造活动破碎带达到标高500 m左右，第二期构造活动是在第一期的基础上继续向上发展，达到标高约670 m的范围。379 cm-1处特征峰半高宽可指示黄铁矿晶体的结晶度和有序度，一般特征峰半高宽越宽其结晶度、有序度越差，黄铁矿结晶沉淀温度越高。从标高430 m至标高500 m，载金黄铁矿在379 cm-1附近峰的半高宽从7.94逐渐增大到12.81，自标高500 m至标高670 m，其半高宽从12.81逐渐减小到8.81。推测与两期构造相对应，存在两期热液活动。通过对标高430 m处的黄铁矿进行电子探针扫面分析，发现确实存在两期热液活动，第一期热液中As元素含量较低，第二期热液As元素含量较高。对标高430 m处第二期热液形成的黄铁矿进行拉曼光谱测试，其A_g为381.86，指示了较低的结晶沉淀压力；半高宽为12.80，指示了较高的黄铁矿结晶沉淀温度。上述事实证实了推测的地质过程。     

An upgraded external beam PIXE setup for multielemental analysis of atmospheric aerosol samples

The external beam particle‐induced X‐ray emission (PIXE) setup has been upgraded by introducing a new silicon drift detector with the aim of obtaining better minimum detection limits (MDLs) at the 2 × 1.7 MV Tandetron accelerator of the Beijing Normal University in China. The upgraded external beam PIXE setup is equipped with two silicon drift detectors for PIXE analysis of low and high Z elements. A surface barrier detector for Rutherford backscattering spectrometry monitors beam and helium flow. Two kinds of aerosol filter samples (quartz fiber filters and Teflon filters) were studied. A 200‐μm thick Mylar absorber in front of the medium‐high energy X‐rays detector was adopted, and it got the best MDLs for atmospheric aerosol samples analysis. Multielemental analysis of quartz fiber filter aerosol samples was achieved. For more accurate and better MDLs of low Z elements in PIXE analysis, it is necessary to keep sufficient helium flow behind the thin samples.     

Determination of the provenance of medieval silver coins: potential and limitations of x‐ray analysis using photons,electrons or protons

One hundred and fifty seven ‘Tiroler Kreuzer’, a medieval currency from the county of Tyrol/Austria, were analysed in order to determine their place of mintage. The silver coins were produced during the 15th century in the mints of Merano (South Tyrol) and Hall (North Tyrol) but they have no marks or punches which would allow a clear distinction. Energy‐dispersive x‐ray fluorescence analysis (EDXRF) was applied without sampling in order to determine the silver contents and also minor (Cu, Pb, Bi) and trace elements (Fe, Au, Hg, Ni). Owing to corrosion processes, which changed the chemical composition of the surfaces of the coins, investigations of cross‐sections were necessary using energy‐dispersive x‐ray microanalysis in a scanning electron microscope (SEM/EDX) to determine the stage of corrosion and the Ag concentration of the core of the coins. The results showed differences of up to 50% between the composition of the core and the surface. Finally, proton‐induced x‐ray emission (PIXE) at an external proton beam was applied, in order to detect also Ni, an element which could not be measured by either EDXRF or SEM/EDX in the ppm range. The data show a clear difference in the Ni content between the coins from Merano (～0.1% Ni) and Hall (～0.01% Ni). Copyright © 2003 John Wiley & Sons, Ltd.     

Estimation of trace elements in some medicinal plants used in anti‐cancer drugs by PIXE

A trace elemental analysis was carried out in various parts of 12 anticancer medicinal plants, using the PIXE (particle‐induced X‐ray emission) technique. A 3‐MeV proton beam was used to excite the samples, and spectra were recorded using a Si (Li) detector. Data analysis was done using the GUPIX software. The elements Cl, K, Ca, Ti, V, Mn, Fe, Ni, Cu, Zn, Br and Sr were identified, and their concentrations estimated. The results of the present study provide justification for the usage of these medicinal plants in the development of anticancer drugs. Copyright © 2012 John Wiley & Sons, Ltd.     

Determination of gold,platinum and uranium in South African ores by high‐energy XRF spectrometry

An automated energy‐dispersive x‐ray fluorescence spectrometer, called the AZTEC, was developed for the non‐destructive determination of gold, platinum and uranium in Witwatersrand ores, by utilizing the high‐energy spectral regions of the K x‐ray lines of these elements. It provides a viable alternative to fire assay, and measures gold concentrations down to <1 ppm. About 100 g of pulverized sample are presented for analysis in a 20 mm diameter tube, and the fluorescent x‐rays are detected by an array of up to 12 high‐purity germanium detectors. Count‐rates of up to 10⁶ counts per second per detector can be processed by the signal processing electronics. The AZTEC technique is a variant of the scattered radiation technique. Concentration is related to peak intensities corrected for background, matrix variations, density and line overlaps. Provided that the samples are finely pulverised, the AZTEC analyses compare well with those obtained by fire assay. Production instruments are being used mainly in the gold mining industry, where they have analysed over 10⁷ samples to date. Copyright © 2004 John Wiley & Sons, Ltd.     

基于元素对研究激光剥蚀-电感耦合等离子体质谱分析硫化物矿物的基体效应

基体效应是影响LA-ICP-MS分析结果准确性的主要因素之一,但目前却没有一种量化基体效应研究的方法。提出了一种以分析元素与内标元素的强度比(I_i/I_is)为纵坐标、浓度比(c_i/c_is)为横坐标绘制I_i/I_is-c_i/c_is图,以元素对I_i/I_is-c_i/c_is图的线性相关系数ｒ量化基体效应的思路。以Fe为内标,考察了13个常用玻璃标准物质与2个硫化物标准及多个硫化物矿物中6个元素对的基体效应,结果显示Cu/Fe和Zn/Fe的线性相关系数r都小于0.99,而痕量元素对Mn/Fe,Co/Fe,Ga/Fe,Pb/Fe的线性相关系数r都大于0.999;以S为内标,考察了2个硫化物标准与多个硫化物矿物中三个主量元素对Fe/S,Cu/S和Zn/S的基体效应,结果显示其线性相关系数r都小于0.999。无论是以Fe为内标结合玻璃标准为外标,还是以S为内标结合硫化物标准为外标分析硫化物矿物,主量元素大多数分析结果的误差大于10%;而以Fe为内标时,绝大多数玻璃标准获得的痕量元素分析结果与MASS-1较为一致,误差小于15%。研究表明,玻璃标准及硫化物矿物标准均与硫化物矿物存在一定的基体效应差异,而采用元素对I_i/I_is-c_i/c_is图的线性相关系数r量化基体效应具有一定的合理性与实用性。研究也表明了以Fe为内标,采用非基体匹配的玻璃标准可用于定量分析硫化物矿物中的痕量元素,尤其是具有较高痕量元素含量的NIST610。