Project ULTRA – Ultramafic Resource Mineral Evaluation
Project ULTRA is led by Professor Bramley Murton of the National Oceanography Centre (UK), and involves a two expedition project aboard the RRS James Cook in order to investigate metallic sulphide deposits formed in magnesium-rich mantle rocks 3km deep at the Mid-Atlantic Ridge. Among the science team are several CREATE members, affiliates, and collaborators, including Dr. Andrew Martin (Memorial University), Dr. John Jamieson (Memorial University), and Dr. Sven Petersen (GEOMAR). The following is a blogpost from Dr. Andrew Martin that details his experience aboard the first expedition of Project ULTRA.
Project ULTRA – Dr. Andrew Martin (April 5, 2022)
Welcome aboard the RRS James Cook! On the 25th of February myself and John Jamieson boarded the James Cook in Southampton, UK, bound for 13°30’ north on the Mid-Atlantic Ridge – a voyage that would take use nearly two weeks to reach our study site! The aim of the research expedition, called “ULTRA – Ultramafic Resource Mineral Evaluation”, led by Bramley Murton of the National Oceanography Centre (UK) is to understand how seafloor hydrothermal deposits form and are preserved in ultramafic-hosted environments. To investigate this we set sail to the Semenov vent field, a site that is hosted on an exposed section of mantle rocks called an oceanic core complex. We arrived on site on the 16th of March ready to start doing some science!
One critical aspect of the research expedition is to explore the “3rd dimension”, i.e., what do the rocks look like below the seafloor? To do this we used the British Geological Surveys Rock Drill 2 – a seafloor drilling system capable of coring to a depth of 50 meters below the seafloor. Rock Drill 2 is a technologically complex bit of kit weighing in at over 6 tonnes! The core recovered from below the seafloor was incredible, so many different alteration mineral assemblages, sulfide minerals and structures, it was completely different to what anyone expected. We also have a remote underwater vehicle called HyBIS onboard. HyBIS is used to survey the seafloor and collect samples – it is amazing seeing how the morphology and lithology exposed on the seafloor changes over a small area. HyBIS data was key in building a geological map of the seafloor, an important component in linking magmatism, faulting and hydrothermal fluid flow.
In between using the Rock Drill and HyBIS, the evenings are spent taking gravity and mega-core samples – a common technique used to collect sediments. These cores are used to understand how the hydrothermal deposits are preserved on the seafloor as iron-rich sediments, that form when sulfide minerals are oxidized by seawater, accumulate in bathymetric depressions, providing a record of how the deposits oxidize over time. We’ve also been busy dredging for samples, this method is great for obtaining bulk rock samples over a relatively large area – we recovered ~100 kg of rocks from the seafloor, mainly basalts.
It’s been a privilege to sail on the RRS James Cook. Having the opportunity to observe such a range of diverse scientific techniques related to seafloor exploration is very exciting. The one thing I will take away from this cruise is just how complex seafloor geology is. This may seem naïve, but the typical “layer-cake” ophiolite stratigraphy is much more complex in reality, or in the case of 13°30’ north, completely different! I think there is a real need to continue to explore the 3rd dimension, every time we drill below the seafloor we redefine our understanding of hydrothermal processes – this research expedition has been no exception!
Andrew Martin
Postdoctoral Fellow, Marine Mineral Resources, Memorial University of Newfoundland
