Introduction to the Special Issue Challenges for mineral exploration in the 21st century: Targeting mineral deposits under cover

The global demand for mineral resources has dramatically increased in the last 50 years. The challenge to keep pace with this demand is the driving force for innovation, and also drives mineral exploration in regions where mineral deposits are under cover, and therefore not exposed or near surface, for which novel techniques are required to locate these mineral deposits hidden beneath this often hundreds of meters thick cover material. Generalizing, regions under cover can be globally divided into three end-member types: (1) regions with intensely weathered cover in tropical or dry (desert and semi-arid) climatic domains (based on Köppen-Geiger's climate classification); (2) regions covered by sedimentary sequences (that can span from the Proterozoic to the Cenozoic) and glacial sediments; and (3) regions under water (seawater, freshwater or ice). This special issue aims to contribute to the debate in the field of mineral exploration in regions that are dominated by and present the complexity of cover by presenting different case studies and technology approaches to detect the distal footprint of mineral systems and deposits at depth.