GGR Biennial Critical Review: Analytical Developments Since 2014

This GGR biennial critical review covers developments and innovations in key analytical methods published since January 2014, relevant to the chemical, isotopic and crystallographic characterisation of geological and environmental materials. In nine selected analytical fields, publications considered to be of wide significance are summarised, background information is provided and their importance evaluated. In addition to instrumental technologies, this review also presents a summary of new developments in the preparation and characterisation of rock, microanalytical and isotopic reference materials, including a précis of recent changes and revisions to ISO guidelines for reference material characterisation and reporting. Selected reports are provided of isotope ratio determinations by both solution nebulisation MC‐ICP‐MS and laser ablation‐ICP‐MS, as well as of radioactive isotope geochronology by LA‐ICP‐MS. Most of the analytical techniques elaborated continue to provide new applications for geochemical analysis; however, it is noted that instrumental neutron activation analysis has become less popular in recent years, mostly due to the reduced availability of nuclear reactors to act as a neutron source. Many of the newer applications reported here provide analysis at increasingly finer resolution. Examples include atom probe tomography, a very sensitive method providing atomic scale information, nanoscale SIMS, for isotopic imaging of geological and biological samples, and micro‐XRF, which has a spatial resolution many orders of magnitude smaller than conventional XRF.     

用对氧的电子探针定量分析值测定石榴子石中Fe~(2+)与Fe~(3+)的含量

本文用对氧的电子探针定量分析值测定了几种石榴子石中Fe~(2+)与Fe~(3+)的含量,讨论了这种新方法中氧的测量精度,详细叙述了实验过程,并与常用的电价差值法和剩余氧计算法进行了比较。     

不可见金的赋存状态研究

电子探针、扫描电镜和溶矿试验研究证明，在某地“卡林型”金矿中，黄铁矿是最主要的载金矿物。黄铁矿由先期形成的含Au和As很低的自形晶核心和后期形成的含Au和As很高的环边组成，其中Au和As呈正消长关系。因此，根据As的分布情况即可研究和认识Au的分布规律。研究结果为改善矿石的氧化焙烧、氯化处理和氰化浸出工艺设计提供了科学依据。     

AUSTRALIS: A new tool for the study of isotopic systems and geochronology in mineral systems

AUSTRALIS (AMS for Ultra Sensitive TRAce eLement and Isotopic Studies) is a microbeam accelerator mass spectrometry (AMS) system designed for in situ microanalysis of geological samples for trace elements and radiogenic and stable isotope data. The AMS method eliminates molecular and isobaric interferences in in situ mass spectrometric measurements, opening up new opportunities in geochronology and tracer applications. Tests have been carried out for measurements of Pb, S and Os isotopes, conducted mainly at 1.5 MV accelerating voltage. In Pb and S tests, precision as high as 0.3‰ has been obtained, made possible by a fast isotope switching system to counter the effect of instabilities in the ion source and beam transport system. In trace‐element analysis, a detection limit for Au at the sub‐ppb level was obtained.     

Natural Clinopyroxene Reference Materials for In Situ Microanalysis

Two clinopyroxene megacrysts, DMP-2 and DMP-3, were collected from Cenozoic alkali basalts in the Hannuoba region of China. They were characterised for major and trace element compositions for in situ microanalysis. EPMA and LA-ICP-MS analyses indicate homogeneity in the element mass fractions in both clinopyroxene samples. Bulk analyses using various techniques (XRF, ICP-OES and solution ICP-MS) also reveal good consistency in their major and trace element data. They, thus, can be used as potential reference materials for elemental in situ microanalysis. Accordingly, element mass fractions are recommended for thirty-two elements.     

Electron Probe Microanalysis of Environmental Samples: Preparation of Reference Materials, Correction for Particle Size Effects and Representative Results on Sediments Recovered from Snow, Power Station Fly Ash and Bone Samples

In this paper we report the results of electron probe X-ray microanalysis (EPMA) that was used to study environmental materials. The mode of preparation and certification of reference samples based on a basaltic glass matrix for environmental applications of EPMA is described. These samples were prepared containing scandium, strontium and barium (from 0.03 up to 7% m/m) and an evaluation was made of homogeneity, their stability to local heating, followed by analysis by independent methods for certification of composition. Matrix correction procedures for the EPMA technique have been developed for particles having a size commensurable with the volume of X-ray generation. An analytical equation for the size factor is proposed and two techniques for selecting optimum conditions for the analysis of environmental samples by EPMA are reported. These procedures provided satisfactory results when utilized in analysing sediments recovered from snow, coal fly ash and the bones of animals and fish, results from which can be used as indicators for evaluating the pollution level of the lower atmosphere, surface and ground water, as well as revealing pollution mechanisms.     

U-Th-Pb副矿物的原地原位测年微束分析方法比较与微区晶体化学研究

系统地对比分析了各种微束分析技术在原地原位测年中的优势和局限性,并对近年发展的微区原位化学测年技术(EPMA)和质子激发X射线微探针分析技术(μ-PIXE)进行了探讨.阐明了矿物微区晶体化学研究的各种方法及其对实现精确原地原位测年的重要性.介绍了北大别黄土岭麻粒岩锆石测定点的晶体化学特征,应用激光剥蚀微探针-感应耦合等离子体质谱(LAM-ICPMS)技术对其进行了锆石的U-Pb表面年龄的测定,结果表明该岩石的麻粒岩相变质发生在2.050 Ga前,锆石来源为多源区.     

Intercomparison of Boron Isotope and Concentration Measurements. Part I: Selection, Preparation and Homogeneity Tests of the Intercomparison Materials

In 1999 the Istituto di Geoscienze e Georisorse (IGG), with the support of the International Atomic Energy Agency (IAEA), undertook the collection, preparation and distribution of eight geological materials intended for a blind interlaboratory comparison of measurements of boron isotopic composition and concentration. The materials came from Italian sources and consist of three natural waters (Mediterranean seawater and two groundwaters) and five rocks and minerals (tourmaline, basalt, obsidian, limestone and clay). The solid materials were crushed, milled and mixed, in preparation for distribution. Extensive assays performed at the IGG on these materials demonstrated that their boron isotopic and chemical compositions are homogeneous.
Additional homogeneity tests were carried out on solid material fragments at the GeoForschungsZentrum Potsdam, with the specific objective of investigating the suitability of some of them for the calibration in situ of micro-analytical techniques. Two materials, B4 (tourmaline) and B6 (obsidian), proved to be isotopically homogeneous and may become excellent references for in situ microanalyses of boron isotopes.
The materials described here were used as the basis of a major laboratory intercomparison study and are now available for further distribution from either the IAEA (solid materials) or the IGG (waters).