Soil gases in mineral exploration: A review and the potential for future developments

To meet the increasing demand for metals to assist in a successful and rapid energy transition, it is crucial to discover more first-class mineral deposits. With most of the world's major deposits occurring near surface, improved methods for detection at deeper levels are required. This paper summarizes the soil gas studies that have been published in English discussing the use of soil gas as a sample medium for mineral exploration. The potential and the reliability of various methods and gas species (O2/CO2, sulphur gases, polymetallic studies, gaseous hydrocarbons, radiogenic daughters (He, Rn), hydrogen and other gases) are reviewed and the challenges for the broad-scale adoption of soil gas measurement as an exploration tool are discussed. Soil gas composition has promising potential for mineral exploration, but much remains to be understood about the origins and processes affecting soil gas composition. There has been a great deal of variation among the studies in sampling and analytical techniques, targeted gas(es), targeted commodities and mineralization type, climatic conditions and environmental settings. Improvement is needed in technical consistency, systematic monitoring of the environmental factors shortly before and after sampling, and the impact of microbes on the composition of the gases. In addition, further study is needed into the impact of climate, the cover composition and structure as well as the biological impact of microbes and plant roots before soil gas composition is a reliable exploration method. Supplementary material: https://doi.org/10.25919/5eww-8f16 Thematic collection: This article is part of the Reviews in Exploration Geochemistry collection available at: https://www.lyellcollection.org/topic/collections/reviews-in-exploration-geochemistry