Discovery voyage DY094: Minerals and life at the Rio Grande Rise

By Bramley Murton, chief scientist

The Rio Grande Rise is a lost land of dinosaurs, ravines and plateaus the size of Wales that formed 72 million years ago by huge eruptions of volcanic lava and drowned 22 million years ago. Now 700 m below sea level, the Rio Grande Rise lies 1400 km east of Brazil, in the South Atlantic. Surrounded by water over 3000 m deep, the relatively shallow Rio Grande Rise is of interest for seafloor mineral deposits rich in iron, manganese and other metals that are important to modern society.

Map showing the location of the Rio Grande Rise and mineral exploration blocks (in red) licensed to the Brazilian Geological Survey (courtesy of GEBCO).

Two of these metals in particular are critical to any future effort to reduce our dependence on hydrocarbons: cobalt and tellurium. Cobalt is essential in rechargeable batteries that are needed if we are to move to electric vehicles. Tellurium is essential for high-efficiency solar-electric power generation. Our voyage aims to enhance understanding of the processes controlling the formation and composition of these deep-ocean mineral deposits and the biology that colonises them.

Cobalt-rich crusts recovered during the MarineE-tech programme in 2016 by the robotic submarine Isis, North Atlantic (courtesy, B Murton).

Cruise DY094 sailed from Santos, Brazil, on the 20^th of October with a scientific team from the National Oceanography Centre, British Geological Survey, University of Edinburgh and the University of Sao Paulo. We have with us the autonomous robotic submarine Austosub6000 and the remotely operated submarine HyBIS. With these machines, we will explore the Rio Grande Rise, mapping it in great detail with our sonars and filming and sampling the seabed mineral deposits and their biology.

RRS Discovery in Santos with the yellow Autosub6000 on the after deck (courtesy: Paul Lusty).

Entering the secure dock areas and boarding the RRS Discovery at the port of Santos, Brazil. RRS Discovery in Santos with the yellow Autosub6000 on the after deck (courtesy: Paul Lusty).

Science team discuss their plans for the voyage while on their way to the Rio Grande Rise, on board the RRS Discovery  (courtesy: Paul Lusty).

Map showing the location of one of our study areas where we have started exploring the sea floor (courtesy of our partners at the University of Sao Paulo).

So far we have seen a varied and fascinating seafloor includes a huge rift over 1500 m deep and 250 km long that cuts the Rio Grande Rise in two, mysterious sinkholes, and the ancient remains of beaches long since drowned under hundreds of metres of water. Although ours is purely a scientific voyage of discovery, our results will tell us a lot about the potential value of the mineral deposits to future renewable energy industries and how vulnerable the life on the seafloor is to mining.