Introduction: New developments in field portable geochemical techniques and site technologies and their place in mineral exploration.
Résumé
There is an ongoing need to be innovative with the way we undertake mineral exploration. Recent technological advances that have enabled successful mineral exploration include on-site or portable instruments, on-site laboratory technologies, various core scanners, and technologies for fluid analysis. Portable or field technologies such as pXRF, pXRD, pNIR-SWIR, µRaman, and LIBS, aid in obtaining chemical and mineralogical information. Spectral gamma tools, a well-known technology, recently took advantage of improved ground and airborne (drone) instruments, to complement hyperspectral imagery. Novel, groundbreaking technology Lab-at-Rig®, was developed by CSIRO, Imdex and Olympus at the Deep Exploration Technologies CRC, and is currently being retrofitted to diamond drilling. Cuttings are separated from drilling fluids in a Solid Removal Unit (SRU), producing one meter composite mud which is sub-sampled, dried and analyzed by both X-ray Fluorescence (XRF) and X-ray Diffraction (XRD) sensors that deliver the chemistry and mineralogy of a sample, respectively. These data are automatically uploaded to a cloud-based storage platform and subjected to a range of statistical analyses with results returned to the geologist in a matter of seconds, allowing decisions to be made in near real time. At a mine site, core scanners become a useful tool to analyse meters of core as it is being drilled. Core scanners include hyperspectral and XRF systems, such as Corescan, HyLogger and Minalyzer CS, for example. Fluid analyses are not as common as analyses of solid materials, but there are advances in such technologies as ASV, polarography, and ion exchange electrodes aiming for analysis of commodity or environmentally important elements. In this session we will introduce some techniques which appeared since 2007 or underwent major progress and discuss their benefits, challenges and pitfalls, why use them and what to expect from them. WHY USING FIELD TECHNIQUES, WHAT TO EXPECT FROM THEM Field portable technologies have seen rapid development over the past two decades, and especially in the last one. This is the result of recent technology advances that made on-site analysis possible and a credible alternative to laboratory work. We provide here a review of the main technologies involved. However, application of field technologies was slower in the more regulated exploration industry because there were quality compromises compared with conventional laboratory technologies, and therefore the same accuracy was not achievable initially. By offering analytical results on the spot, in almost real time, on-site technologies fit the increasing needs of exploration teams for fast information that provides decision making support during field work and drilling operations, and sample screening before laboratory requests. The gain in time and flexibility, even without any consideration of lower analytical costs, has a significant impact on the efficiency and cost-effectiveness of field operations, especially in remote areas. For instance, field analyses allow the selection of the most promising formations (Gałuszka et al., 2015, Zhang et al, 2017), stream or soil areas, and to focus immediately on potential targets. At a drill site, they help the geologists to identify target formations, to sample mineralised sections more precisely, and to stop drilling when necessary. Benefits are therefore expected for field costs and the length of operations. But the most important benefits are for exploration efficiency, and for improved chances to hit targets, due to continuous feedback of information. SOME TECHNIQUES WHICH APPEARED SINCE 2007 OR UNDERWENT MAJOR PROGRESS Analytical technologies designed for the laboratory are increasingly adapted for on-site use, in order to address mineral exploration needs for faster or more efficient decision making (Lemiere, 2015). This includes elemental and mineralogical solids analysis, water analysis, and other more integrated strategies. The scope of this presentation covers handheld instruments, able to operate in the field, and site portable instruments, able to operate at remote sites, with limited logistics. All should provide decision-making results within minutes or on the same day as sampling and analysis. The fast evolution of technology implies that many of them were far less advanced or even non-existent for Exploration'07.
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