GEOLOGICAL FATE OF SEAFLOOR MASSIVE SULPHIDES AT THE TAG SEGMENT (MID-ATLANTIC RIDGE)

Submarine polymetallic massive sulphide deposits (SMS) are one of the oldest known mineral deposit types, having formed some of the largest deposits in Earth history. They are characterised by a diverse metal content, especially they are rich in strategic metals used in the electronic and green industry. Due to a growing global demand supply shortages are an identifiable risk for the economy and therefore new SMS deposits need to be discovered, explored and mined to secure the metal supply in a fast changing global economy.

Today 65 percent of SMS are formed in hydrothermal vent sites along mid-ocean ridges in extensional terrains. Currently, exploration parties predominately target active deposits as they can be easily identified by tracing hydrothermal related chemical and physical changes in the water column but due to their unique fauna, concerns regarding environmental impacts are growing. Extinct SMS deposits where hydrothermal activity has ceased (eSMS) are not colonised by any type of vent fauna and are likely to have higher metal concentrations as they have gone through a complete hydrothermal cycle including remobilisation and enrichment of metals. As these eSMS are under cover, fundamental questions arise such as the whereabouts, sub-surface structure, alteration, and preservation processes of the sulphides after hydrothermal activity ceased, as well as assessments of available resources are lacking resulting in an underestimation of the global metal resources.

These questions are being addressed by the Blue Mining project, funded by the European Union’s Seventh Framework Programme. Sub-seafloor imaging techniques and seafloor drilling will be used to investigate and compare several hydrothermally dead, eSMS deposits at the TAG segment (26°N, Mid-Atlantic Ridge) during two research cruises from early May to late August 2016. The findings of this unique research programme can then be translated into effective exploration and resource estimation techniques for future sustainable deep-sea mining of eSMS.