Deep-sea sediments may serve as potential indicators for discovering nearby seafloor massive sulfide (SMS) deposits.
Researchers have found that seafloor sediments adjacent to active and recently inactive hydrothermal vents generally contain higher metal concentrations compared to those that are farther away from such features.
The two main mechanisms that generate metalliferous sediments are plume fallout and mass wasting. Both processes create spatial geochemical variations that could serve as indicators for locating SMS sites.
At the Deep Sea Minerals conference in Bergen in April, PhD student Acer Figueroa (National Oceanography Centre and University of Southampton) will present some of the latest findings from the ULTRA project.
Participants in the project conducted sediment coring during two expeditions in 2022 and 2023 at the Semenov Hydrothermal Field, which is located at approximately 13°N along the Mid-Atlantic Ridge.
Core analysis revealed three styles of SMS mineralization:
- Inactive SMS mounds that lack hydrothermal input at the surface but display deeper mineral signatures.
- Recently inactive SMS mounds, where hydrothermally influenced sediments decrease in concentration as you move away from the mounds.
- Mineralized fault zones, characterized by metal-enriched sediments that diminish in concentration away from the fault.
Metal enrichments were detected up to 1 km away from the recently inactive mounds and at least 200 meters from the fault zones.
Figueroa will also highlight an intriguing observation from some of the gravity cores: a previously undescribed black layer. This 35-centimeter layer, which may extend over hundreds of meters, is heavily enriched in copper minerals, with concentrations reaching 60 weight percent.
The supergene (close to the surface) black layer appears to have been preserved by overlying sediments and could potentially serve as both an exploration marker and a co-product for SMS mining.
In summary, the researchers believe that coring and sediment studies at and distal to SMS deposits may offer a meaningful, cost-effective exploration tool.
Norwegian participants in Project ULTRA are the University of Bergen, Equinor, and Green Minerals. Other partners include the National Oceanography Centre, the British Geological Survey, the universities of Cardiff, Southampton, Leeds, and the Memorial University (Canada), as well as GEOMAR (Germany).
Deep Sea Minerals 2025 will take place in Bergen from 1-3 April. The program and registration page can be found on the conference website.