11th International Conference on Methods and Applications of Radioanalytical Chemistry (MARC XI) introduction

Nuclear terrorism has led to newer investigative methods for building national nuclear forensic libraries. The objective of this work was to resolve these signatures by applying the ICP-MS for isotope ratio (IR) analysis on uranium containing samples. Lead (Pb) isotope ratios for the studied gold mine has ²⁰⁷Pb/²⁰⁴Pb values between 13–20 and ²⁰⁶Pb/²⁰⁴Pb values ranging from 16–25, which confirm that the Carletonville gold fields are of uraninite detrital pyrite deposits. Trace elemental concentrations indicated a pyrite type of uranium deposit. Uranium in the deposit exhibits geochemical signatures of the radiogenic formations of the ore enhanced in ²⁰⁶Pb.     

黔西南卡林型金矿床稀土元素地球化学特征

分析了黔西南地区板其、、丫他及戈塘等卡林型金矿床的(La/Yb)N、(La/Sm)N、∑REE及LREE/HREE等稀土元素的含量及参数特征.结果表明,该区金矿床相对富集LREE;该区戈塘金矿具有明显的MREE富集及正Eu异常的特点,表明成矿热液应该是一种还原性流体,来源于深部或至少经历过对富含斜长石源区的水-岩反应矿...     

富蕴县阿克塔斯铜金矿床火山岩地球化学

阿克塔斯铜金矿区位于新疆富蕴县内,矿区主体位于东准噶尔北部,靠近阿尔泰与北准噶尔两个具有不同构造特征和演化历史的构造单元。阿克塔斯金铜矿体主要赋存于石英脉、斜长花岗岩、蚀变安山岩及接触带内的千枚岩破碎带中。根据安山岩的微量元素分配模式的研究发现,岩浆在演化的过程中有大陆地壳的物质加入其中并进行混染。通过对含矿石英脉中黄铁矿和黄铜矿中的硫进行同位素分析,表明黄铁矿、黄铜矿中硫可能都来源于地幔。矿区区域地球化探异常发育,金、铜、砷元素含量高、相关性好,并与火山―岩浆岩有密切空间关系,是寻找评价与火山岩以及浅成岩有关铜金矿的有利地段。     

Substoichiometric determination of traces of gold by radioactive isotope-dilution analysis

A radioactive isotope-dilution method for the determination of traces of gold has been developed. It is based on the solvent extraction of gold diethyldithiocarbamate from 0-5N sulphuric acid containing ascorbic acid, by means of a substoichiometric amount of zinc diethyldithiocarbamate in chloroform. The separation has been applied to the analysis of gold-doped semiconductor-grade silicon and of gold-bearing ores. Amounts of gold down to 5 x 10(-7)g 20 ml of test solution can be determined.     

Multielemental automated INAA system for gold ore samples

A methodological approach to the activation analysis of bulk samples up to 300 g mass on a reactor is proposed. As applied to the analysis of massive gold-bearing ore samples, the questions of representativity of the samples with inhomogeneous distribution of the component under examination, specific effects caused by gold particles as well as large sample dimensions and mass are studied and ways for taking into account their influence are suggested. An automated system of multielemental neutron activation analysis of large samples of gold-bearing ores has been developed. The system has found application in geological prospecting and the mining industry.     

Improvements in the Grinding of Gold-Bearing Geochemical Samples and Their Sampling for Fire Assay

The effect of fine grinding of gold-bearing geochemical samples on the representative sample size and the recovery of gold and silver in fire-assay fusion was studied experimentally. A method is proposed for the improvement of grinding and sampling procedures in fire assay.     

Analysis of geological samples by the micro-PIXE facility at KFUPM

Summary The scanning microprobe facility of the 3 MV Tandetron accelerator at King Fahd University of Petroleum and Minerals (KFUPM) has been applied extensively in various fields, including geology. This paper reviews a number of geological investigations carried out on samples of gold-bearing rocks, phosphorite ores and volcanic sediments. Elemental composition and distribution maps across single mineral grains, fluid inclusions, grain boundaries and matrices were measured. The microscopic data obtained are discussed to understand fundamental geological processes and ore genesis, and the provenance of economically important trace minerals contained in these samples.     

土壤地球化学在广南斗月金矿中的应用

对现已发现的超大型金矿和国内金矿资源进行统计,结果表明,大型、超大型矿床中与微细浸染型金矿相对应的金矿成因类型(如渗滤热液型金矿、含碳浅变质碎屑岩型金矿等)占有很大比例。因此开展对微细浸染型金矿的研究和找矿具有重要的实际意义。在广南斗月金矿开展1∶10000土壤地球化学测量(简称化探),了解测区以Au为主的As、Sb、Hg、Ag土壤地球化学背景,确定化探异常下限,圈定Au、As、Sb、Hg、Ag化探(次生晕)异常,根据各异常面积的大小、浓度的高低以及五个元素异常套合(组合)情况等综合因素,对化探综合异常进行评序和分级,结合地质简测等地质资料的综合研究分析,判别具有潜在找矿价值的异常区,为进一步地质勘探工作提供靶区。     

Kerogen as a geochemical marker of the thermal history of rocks

The study presents examples of the application of oxyreactive thermal analysis to the geological prospecting of bitumen deposits. Thermal analysis performed under properly chosen analytical conditions allows determination of characteristic features of organic matter and, at the same time, estimation of the thermal history of rocks. Thermal oxyreactivity curves document whether rocks were heated before or not. The results of the oxyreactive thermal analysis correlate well with the results of routine chemical analyses of organic matter (e.g. the composition of kerogen and bituminous fraction, Rock-Eval analysis and others). Our study clearly demonstrates that the composition of organic matter in facially, lithostratigraphically, and biogenetically identical rocks depends on their thermal history.     

云南老王寨金矿区煌斑岩稀土地球化学特征

广泛分布于云南老王寨金矿区的煌斑岩可分为新鲜（弱蚀变）、蚀变、矿化三种,虽然碱种煌斑岩稀土含量范围、分配模式为相似的富轻稀土型,但在ＬＲＥ／ＨＲＥ、ＮＬａ／Ｙｂ等参数也存在一定的差异。新鲜煌斑岩稀土地球化学研究表明,本区煌斑岩为富集地幔不同部分熔融程度的产物;煌斑岩蚀变、矿化过程中稀土元素活动规律的质量平衡计算结果表明,该区煌斑岩的蚀变流休和矿化流体均含有一定量的稀土元素,这些流体主要为伴随煌斑岩     

Characterization of self-assembled monolayers of fullerene derivatives on gold surfaces: implications for device evaluations

The widely employed approach to self-assembly of fullerene derivatives on gold can be complicated due to multilayer formations and head-to-tail assemblies resulting from the strong fullerene-fullerene and fullerene-gold interactions. These anomalies were not examined in detail in previous studies on fullerene self-assembled monolayers (SAMs) but were clearly detected in the present work using surface characterization techniques including ellipsometry, cyclic voltammetry (CV), and X-ray photoelectron spectroscopy (XPS). This is the first time that SAMs prepared from fullerene derivatives of thiols/thiol esters/disulfides have been analyzed in detail, and the complications due to multilayer formations and head-to-tail assemblies were revealed. Specifically, we designed and synthesized several fullerene derivatives based on thiols, thiol acetates, and disulfides to address the characterization requirements, and these are described and delineated. These studies specifically address the need to properly characterize and control fullerene-thiol assemblies on gold before evaluating subsequent device performances.     

Endlagerung radioaktiver Abfälle

Shales, granites and rock salt are currently under investigation as host rocks for radioactive waste. With respect to heat‐producing waste (spent fuel, high‐active waste) these rock types comprise contrasting mechanical and chemical behavior. The differences are due to the respective geological formations: Shales form by slow accumulation of fine‐grained minerals from seawater with subsequent compaction and diagenesis; crystallization of deep‐seated magmas at 700 to 850°C is the process that generates granitic rocks in the upper 20 km of the earth's continental crust; rock salt is a chemical sediment which forms by precipitation of chloride and sulfate minerals from seawater evaporation in shallow marine basins under arid conditions. The extent of chemical reactions between granitic rocks and migrating saline fluids upon canister‐induced heating is quite small. However, thermally induced reactions between sheet silicate minerals in shales may result in a gradual loss of adsorption capacities for released radionuclides. Canister‐induced temperature gain in rock salt results in increasing creep rates which lead to an enhanced enclosure process. Great care has to be taken in the selection of salt formations as host rocks with respect to brines; depending on their composition and temperature brines might react with e.g. potash‐seams.     

Thick oxide growth on gold in base

The formation of thick oxide films (ca. 100 monolayer equivalents at 2.3 V) on a gold anode was observed under steady-state polarization conditions in base. As reported by other authors for acid, the layer produced was of duplex character with a compact, largely anhydrous inner film at the metal surface, and a much thicker, porous, highly hydrated outer film at the oxide-solution interface. These deposits were readily distinguished, and quantified coulometrically, due to differences in reduction potential under cathodic sweep conditions. The onset of thick film growth occurred in a potential region where linear Tafel behaviour is observed for oxygen gas evolution on gold, and changes in oxygen coordination of cations in the outer region of the compact layer under these conditions is assumed to enhance the conversion of material in the outer region of the latter to the more hydrated form. As compared with acid, oxide growth was much slower (and reached a limiting value) in base, the outer film was reduced less readily and inhibition of oxygen gas evolution in the thick film region (at ca. 2.35 V) was observed. The results were accounted for by assuming increasing hydroxide ion coordination by cations in the hydrous layer with increasing pH — the more highly coordinated species being thermodynamically more stable but kinetically less capable of rearranging to form a crystalline product. The relationship between the hydrous film on gold and those produced on a wide range of other transition metals is briefly outlined.     

Amyloid-mediated synthesis of giant, fluorescent, gold single crystals and their hybrid sandwiched composites driven by liquid crystalline interactions

We report for the first time on the templating effect of β-lactoglobulin amyloid-like fibrils to synthesize gold single crystals of several decades of μm in dimensions. The gold single crystals were produced by reducing an aqueous solution of chloroauric acid by β-lactoglobulin amyloid protein fibrils. Atomic force microscopy, conventional and scanning transmission electron microscopy, electron diffraction and optical microscopy techniques were combined to characterize the structure of the gold crystals. The single-crystalline features of these macroscopic gold crystals are witnessed by their distinctive hexagonal and triangular shape and are confirmed by selected area electron diffraction (SAED). UV-vis absorption spectrum, recorded after a reaction time of 6h at the heating temperature of 55°C showed a surface plasmon resonance peak at 540 nm. With the increase of reaction time to 24h, the absorption spectrum peaks shift to a very broad and higher wavelength region extending up to near infrared region. Remarkably, these single crystalline gold crystals show auto fluorescence when illuminated to UV lamp. Further increase in β-lactoglobulin amyloid fibrils concentration above the isotropic-nematic transition, drives the formation of gold single crystals microplates stacking together and self-assembling into new hierarchical, layered protein-gold hybrid composites.     

Distribution pattern of REE and other elements in the host rocks of the Gubrunde uranium occurrence,NE Nigeria

Prospecting for high grade uranium deposits in NE Nigeria has over the years among other reasons been handicapped by lack of adequate understanding of the elemental primary dispersion pattern associated with known occurrences in this region. Thirty six samples from a low grade uranium occurrence at Gubrunde consisting of disseminated ores and hostrocks were therefore analyzed for 38 elements by NAA, DNAA, EDXRF and flame AAS techniques. The analytical data were evaluated using multivariate statistical techniques. The results show three element groupings (associations). The first group consists of Pb, Ba, Ce, Sm (LREE), that are enriched with increasing uranium concentration in the mineralized zone and are therefore capable of serving as pathfinder elements for uranium. The second group comprising of MgO, K₂O, CaO, Na₂O and the HREE are depleted in the mineralized zone due to action of hydrothermal fluids and are indicative of altered/mineralized rocks. The third group consists of the rest bulk of elements which feature little or no significant enrichment with increasing uranium but associate with ferruginization (haematite) and possibly refractory minerals.     

Ore-controlled Mechanism and Geochemical Characteristics of Gold-bearing Formation in Northwest Jiangxi Terrain

Based on the geological and geochemical studies on the Middle Proterozoic Jiuling Group in the Northwest Jiangxi Terrain, it is ascertained that this group is a kind of Au-bearing formation with Au-Ag-As association, and the volcanism is the key to its foundation. The Jiuling Group can be divided into two geochemical groups: high-Au layers and low-Au layers, which is due to the inhomogeneous metamorphic reformation. The discriminant functions F_1& F_2 can be established by means of Au, Ag, As, Ti, Cr, V, etc. eleven elements, and the diagram of F_1-F_2 is the distinguishing sign of the Au-bearing formation. Based on the systematic studies on two types of gold mineralization, namely, solo gold with metamorphic fluid and Au, Ag, etc. polymetallic association with magmatic fluid, the authors establish the metallogenic model of gold deposits in the area.     

Heavy metal pollution from phosphate rock used for the production of fertilizer in Pakistan

Phosphate rock belongs mainly to sedimentary, slightly to igneous, and negligibly to metamorphic rocks. It is used for the production of phosphorous based fertilizers, acids, detergents and many products of common use. The rock is mainly composed of phosphorous and minutely of many other elements. The aim of this study was to determine the concentration of Cd, Cu, Cr, Ni, Pb, Zn (environmental pollutants i.e. toxic elements), and Co, K, Mg, Mn, Na (common elements) in phosphate rocks used for production of fertilizer in Pakistan. Rock samples of local origin were collected from the geological rock formations around the city of Abbottabad and those of foreign origin were obtained from the fertilizer factories and research institutes in Pakistan. Analysis of phosphate rock for all the elements of interest was carried out with Flame Atomic Absorption spectrometer (FAAS) except for sodium which was analyzed using Flame Photometer, while the concentration of potassium was determined using both the techniques. The results showed that heavy metal content was lower in Pakistani phosphate than that in imported rock and were below the safe limits with the exception of lead whose concentration was found to be higher in local phosphate deposits than that in imported rock samples. Phosphate rock is a source of heavy metal pollution of air, soil, water, food chain etc, therefore requires removal of heavy metals (HMs) from the rock prior to its use.     

The gold-ammonia bonding patterns of neutral and charged complexes Au m 0+/-1-(NH3)n. I. Bonding and charge alternation

The gold-ammonia bonding patterns of the complexes which are formed between the ammonia clusters (NH(3))(1< or =n< or =3) and gold clusters of different sizes that range from one gold atom to the tri-, tetra-, and 20-nanogold clusters are governed by two basic and fundamentally different ingredients: the anchoring Au-N bond and the nonconventional N-H...Au hydrogen bond. The latter resembles, by all features, a conventional hydrogen bond and is formed between a typical conventional proton donor N-H group and the gold cluster that behaves as a nonconventional proton acceptor. We provide strong computational evidence that the gold-ammonia bonding patterns exhibit distinct characteristics as the Z charge state of the gold cluster varies within Z=0,+/-1. The analysis of these bonding patterns and their effects on the N-H...N H-bonded ammonia clusters are the subject of this paper.     

Formation of Au nanorods and nanoforks over MgO support

Summary Nanosized Au particles were prepared by various methods on MgO. Beside the formation of hexagonal particles, impregnation deposited gold on the supports as rod- and fork-shaped crystals of the nanometer size. The growth of these unusual formations is probably directed by the cracks in the layers of the support, but it must also be the inherent property of the deposited metal.</o:p>     

Resonance light scattering properties of Eu3+ in gold colloid

Gold colloidal containing rare-earth ions Eu3+ were prepared at room temperature. Fluorescence spectra and resonance light scattering (RLS) spectra of Eu3+ ions and gold colloid containing Eu3+ were measured. For solution containing Eu3+, RLS features show two peaks at the edges of the visible light wavelength region. The short wavelength peak takes place at about 400 nm and the longer wavelength peak is the corresponding 1/2 fraction frequency RLS peak, which takes place at about 780 nm. When gold colloids were added to the solution containing Eu3+, both these two RLS peaks were enhanced. We believe that the energies, which are absorbed by the surface plasmon resonance in the gold nanoparticles, are efficiently transferred into the Eu3+ ions to cause the increased scattering.