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Global-scale, or continental-scale, geochemical surveys cover millions of square kilometers of the Earth’s surface generally at a very low sample density (1 site per 1,000 to 10,000 km2). Geochemical patterns produced from these low-density surveys reflect processes that act at the broad scale of sampling. These processes are related to many factors including tectonics, climate, weathering, geochemical and mineralogical composition of the original soil parent material, continental-scale glaciation, topography, regional-scale alteration and mineralization, and in some cases, human activity. A multi-element geochemical atlas of the Earth’s land surface based on this type of survey has been a topic of discussion among applied geochemists since the 1980s. Over the past 15 years, several global-scale geochemical surveys have been conducted (Australia, China, Europe, India, Mexico, United States of America) and the data and maps are being used as a tool to aid in environmental and resource management. In 2016, the establishment of both the International Union of Geological Sciences (IUGS) Commission on Global Geochemical Baselines and the United Nations Educational, Scientific and Cultural Organization (UNESCO) International Centre for Global-Scale Geochemistry has provided a hopeful future for continuing global-scale geochemical mapping in other parts of the world, with the ultimate product being a global geochemical database and atlas derived from this data set.

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. Finally, it is emphasised that the success of any geochemical survey, including global geochemical baseline mapping, depends on the training of the applied geochemist.