Trace Element Analysis of Minerals in Magmatic-Hydrothermal Ores by Laser Ablation Inductively-Coupled Plasma Mass Spectrometry: Approaches and Opportunities

Nigel Cook,Cristiana Ciobanu,Kathy Ehrig,Luke George,Benjamin Wade,Zhi-Yong Zhu

doi:10.3390/min6040111

Abstract

Laser ablation inductively-coupled plasma mass spectrometry (LA-ICP-MS) has rapidly established itself as the method of choice for generation of multi-element datasets for specific minerals, with broad applications in Earth science. Variation in absolute concentrations of different trace elements within common, widely distributed phases, such as pyrite, iron-oxides (magnetite and hematite), and key accessory minerals, such as apatite and titanite, can be particularly valuable for understanding processes of ore formation, and when trace element distributions vary systematically within a mineral system, for a vector approach in mineral exploration. LA-ICP-MS trace element data can assist in element deportment and geometallurgical studies, providing proof of which minerals host key elements of economic relevance, or elements that are deleterious to various metallurgical processes. This contribution reviews recent advances in LA-ICP-MS methodology, reference standards, the application of the method to new mineral matrices, outstanding analytical uncertainties that impact on the quality and usefulness of trace element data, and future applications of the technique. We illustrate how data interpretation is highly dependent on an adequate understanding of prevailing mineral textures, geological history, and in some cases, crystal structure.

Highlights

Significant advances have taken place in laser ablation inductively-coupled plasma mass spectrometry (LA-ICP-MS) over the past two decades ([1] and references therein)
Significant differences in trace element distribution between ore systems can be related to temperature evolution, abundance of sulphides and availability of other minor elements (As, Te, Bi, etc.)
Datasets for Fe-oxides in iron oxide-copper-gold (IOCG) deposits—the fact that they are probably the only minerals that are continuously generated and reworked through cycles of brecciation. Such cycles will induce trace element heterogeneity associated with dissolution, recrystallization, pseudomorphic replacement and release of trace elements that will overprint pre-existing grains at the scale of the polished block. We demonstrate this variation by two contrasting examples of hematite from high-grade bornite ore at Olympic Dam, which have been dated by hematite Pb–Pb geochronology [7]

Summary

Introduction

Significant advances have taken place in laser ablation inductively-coupled plasma mass spectrometry (LA-ICP-MS) over the past two decades ([1] and references therein). Instruments have become widely available in laboratories worldwide and the number of applications in Earth science has been greatly expanded by ongoing technological development, with respect to analysis speed, resolution and sensitivity, and by the availability of reliable reference materials designed for specific purposes. The LA-ICP-MS method is cost-effective compared to other techniques, such as secondary ion mass spectrometry (SIMS). For these reasons, LA-ICP-MS has rapidly established itself. Minerals 2016, 6, 111 as the method of choice for generation of multi-element datasets for specific minerals. Applications have expanded from trace element ‘spot’ analysis to mapping of areas within a sample, greatly assisted by the widespread availability of software, such as iolite [2]. LA-ICP-MS-based geochronology is rapidly being extended to other dateable minerals, including hematite [7,8], apatite [9], cassiterite [10], and epidote-group minerals [11]

Results

Discussion

Conclusion