Field Analytical Techniques for Geochemical SurveysReport as inadecuate




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1 BRGM - Bureau de Recherches Géologiques et Minières

Abstract : Obtaining geochemical results in the field has been a persistent dream for exploration geologists in the last century, and a few practical geochemical? tests were developed, but shipping samples to faraway labs and waiting weeks for results was the rule. This remained a dream until around 1990, when technology developments of portable instruments allowed on-site measurement of the first key metals in solids. This development progressed rapidly and by 2010, most geochemists could have access to portable field analytical methods, if they decided so. These instruments were soon used for environmental investigations too. At the same time, field instruments for water analysis were developed, with applications in the environmental, ore processing and exploration domains. Impassioned debate followed development since 1995 about the quality of field analyses vs. laboratory analyses, with often non-neutral contributions from instrument suppliers and from the laboratory profession. Beyond instrument limitations, it appeared soon that sample preparation and sample representativeness were key issues to interpret field analytical results. This is still the case today, even if documented evidence of field-lab concordance is frequently published – by geochemists who pay attention to sample preparation and representativeness. The late apparition of relevant standards, to the notable exception of EPA 6200 1998, did nothing for a smooth acceptance of field methods or their beneficial introduction in the analytical toolbox of applied geochemists. Benefits of field analysis comprise in-situ analysis, without transport issues, implementation of dynamic and adaptive sampling plans along results collection Robbat, 1997; Crumbling, 2001; US-DOE, 2001, Triad, increase of data density and quality through larger data sets and better representation of transient phenomena.Possible pitfalls include improper interpretation of field data as a result of insufficient understanding of the sampling and measurement processes, use of heterogeneous data sets collected by different methods, and the lack of critical examination of data.Current developments of new or adapted technologies cover mineralogy portable XRD, micro Raman, IR spectroscopy, light inorganic elements LIBS, pXRF, organic substances IR spectroscopy, GC, GC-MS and more focused applications.Field techniques offer their best value when they cooperate with the laboratory throughout the investigations.





Author: Bruno Lemière -

Source: https://hal.archives-ouvertes.fr/



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