General concepts of geochemical mapping at global, regional, and local scales for mineral exploration and environmental purposes

Abstract

RESUMOO planejamento de uma campanha de amostragem geoquímica eficaz para atender aos objetivos da pesquisa deve se basear no uso escalonado ou gradual dos métodos geoquímicos aplicados, a partir de um estudo de escritório da área de trabalho que coleta e avalia todos os dados e informações disponíveis. Isto é seguido por uma investigação de campo, que deve começar com um estudo orientativo, no qual uma variedade de meios amostrais, técnicas de preparação de amostras e protocolos analíticos são testados com o objetivo de encontrar a metodologia mais eficaz em termos de custo a ser aplicada nas etapas seguintes do follow-up e de pesquisa de detalhe. A amostragem é a parte mais importante em qualquer pesquisa geoquímica para fins de exploração mineral ou de diagnóstico ambiental. Além da amostragem, outra parte significativa de uma pesquisa é a preparação da amostra. Erros na amostragem e preparação da amostra são difíceis de rastrear e afetam os resultados finais e o sucesso de uma pesquisa. Portanto, estas são as duas partes de uma pesquisa geoquímica que devem ser realizadas com o máximo cuidado. São descritos procedimentos de amostragem para sedimentos de riachos, sedimentos de superfície ou de várzea, águas de riachos, águas subterrâneas, rochas e solos residuais, bem como amostragem em laboratório. A importância da randomização de amostras e implementação de procedimentos rigorosos de controle de qualidade também são discutidos. Finalmente, enfatiza-se que o sucesso de qualquer levantamento geoquímico, incluindo o mapeamento geoquímico global, depende das capacitação do geólogo como geoquímico aplicado. Palavras-Chave: levantamento geoquímico, amostragem, preparação de amostras, controle de qualidade, exploração mineral ABSTRACT Planning an effective geochemical sampling campaign to meet survey objectives should be based on a phased or stepwise use of applied geochemical methods, starting from a desktop study that collects and evaluates all available data and information. This is followed by a field investigation, which should begin with an orientation survey, where a variety of sampling media, sample preparation methods, and analytical protocols are tested with the objective of finding the most cost-effective methodology to be applied in the succeeding steps of the follow-up and detailed investigations. Sampling is the most important part in any geochemical survey for mineral exploration or environmental purposes. Apart from sampling, another significant part of a survey is sample preparation. Mistakes in sampling and sample preparation are difficult to trace and affect the final results and success of a survey. Hence, these are the two parts of a geochemical survey that should be performed with the utmost care. Sampling procedures for stream sediment, overbank or floodplain sediment, stream water, ground water, rock, and residual soil are described, as well as sampling in the laboratory. The importance of randomisation of samples and implementation of strict quality control procedures are also discussed. Fi...

Detection of REEs with lightweight UAV-based hyperspectral imaging

“…The specimens are then sent to laboratories for whole-rock geochemical analysis. The mapping and geochemical analyses occur before drilling and can be costly and time-consuming 31 . Our solution can give the field geologist a rapid estimation of relative REE distribution and thus improve the sampling strategy by identifying zones of high REE concentrations within the rock outcrops.…”

Geochemical background - what a complex meaning has such a simple expression!

“…Geochemical surveys use some well-known sampling media to describe the distribution of chemical elements or compounds in an area. Each sampling medium (Figure 1) has properties, accordingly to its constitution, and capacities in terms of its representativeness and the influence it suffers from abrupt changes in local climatic conditions (DEMETRIADES et al, 2018).…”

“…Planned in this way, the survey will produce a necessary and sufficient geochemical database for the calculation of statistical estimators, or for reliable surfaces to be estimated, representing the background with the necessary reliability. As the base maps are being detailed and improved, the background can be recalculated for the new geological, pedological or land use units (DEMETRIADES et al, 2018).…”

Methodological approach and general guidelines to geochemical mapping and background-baseline analysis for environmental assessment: a case study in the Carajás Mineral Province, Brazil

“…In addition to the experience established by geological surveys in regional geochemical studies around the world, several studies have been carried out on geochemical mapping at continental and regional scales (Birke et al 2015b, Liu et al 2015, Woodruff et al 2015. Continental mapping scales range from 1:10,000,000 (1 sample/10,000 km 2 ) to 1:5,000,000 (1 sample/1,600 km 2 ), while regional mapping scales range Methodological approach and general guidelines to geochemical mapping and background-baseline analysis for environmental assessment: a case study in the Carajás Mineral Province, Brazil from 1:1,000,000 (1 sample/100 km 2 ) to 1:10,000 (1 sample/10,000 m 2 ) (Demetriades et al 2015(Demetriades et al , 2018. Geochemical mapping data are typical geospatial data, where X and Y represent geographic coordinates and Z represents geochemical attributes, and the development of computational geographic information system (GIS) platforms has facilitated the manipulation of geochemical data and geospatial statistical analysis (Smith et al 2018).…”