Modern an ancient VMS-forming hydrothermal systems

Publicerad: 11 januari 2016

Coordinator: Iceland GeoSurvey (ÍSOR)

Participants:

Geological Survey of Norway  (NGU)

Geological Survey of Sweden (SGU)

Geological Survey of Denmark  and Greenland (GEUS)

University of Bergen (UiB)

Norwegian University of Science and Technology (NTNU)

SINTEF

University of Iceland

Geological Survey of Finland (GTK)

Jardfeingi- Faroese Earth and Energy Directorate

Summary

 

VMS deposits (volcanic massive sulphide)  are and have been a key source for many important metals,such as copper, zinc, gold and silver. Almost all VMS mining activities have been on land,and are related to onshore deposits,or represent old oceanic vent systems,abducted onto continents during plate tectonic  events. As need for these resources rises,interest in mining active or young systems on the sea floor is likely to increase. With this in mind it is paramount that we build up the knowledge bank for potential offshore VMS deposits. Knowledge of the onshore resources, exploited for hundreds of years,will be fundamental to future mining in the deep sea,and conversely, monitoring and studies of the active processes on the sea floor will increase our understanding of onshore resources.

The aim of this project is to develop new sensitive technologies for on- and offshore exploration and environmental monitoring, giving new insight into deposit characteristics and how the deposits are distributed and formed  in 2D, 3D and possibly 4D. An important part of the project will be building a bridge between on- and offshore systems by acquiring new knowledge and understanding that benefits both on- and offshore exploration and mining. Main focus will be on the ore forming systems, the hydrothermal mechanisms and the geodynamic systems that drive them.

Mineral exploration for undiscovered VMS deposits needs to be based on characterization of VMS ore forming systems. Further knowledge of the metal sources, transportation and deposition within VMS systems is required. We also need a better understanding of the preservation potential for VMS deposits, as well as refining the geological, geochemical and geophysical source indicators and vectors that allow effective targeting of VMS ore deposits.

Geodynamic and tectonic setting of VMS-deposits is another key issue for discovery of new deposits, both in young or active VMS systems, as well as in the classical onshore VMS deposits.

Mineral prospectivity mapping (MPM) and mineral resource assessment (MRA) are two predictive modelling processes for deriving information that is essential for strategic planning in mineral exploration and development. MPM, which could be either data- or knowledge driven,aims to model the prospectivity or likelihood of mineral deposit occurrence regardless of size or grade. MRA aims to (1) outline  geologically permissive terrains where certain types of mineral deposits  likely exist, (2) estimate the amount of metals in geologically permissive terrains and (3) estimate the number of undiscovered mineral deposits of each type within geologically permissive  terrains.

Seafloor massive sulfide (SMS) deposits represent a potential future source for base and precious metals. The extent of this resource is highly debated and estimates of the total deep sea Cu-Zn resource range from 530 GT to 3 GT- with only 30 MT being accessible. Still, the first vessel designed for mining SMS deposits is currently being built. Norway, Iceland and Greenland have around 5% of the global mid-ocean ridge system within their national waters. A number of hydrothermal systems and associated SMS deposits have been discovered along these ridges in recent years. Until now, only parts of the ridge system present within Nordic waters have been systematically explored for hydrothermal activity and possible SMS occurrences. In order to better constrain the available resources, new effective search strategies have to be tested and further developed, and larger ridge segments have to be systematically explored.

A major issue with deep sea mining is the complete lack of knowledge on environmental consequences. Environmental impacts may result from the mining activities directly at the seafloor through habitat  removal, plume generation, noise/vibration and reduced water quality and an assessment will be made on the environmental impact encountered when we perform our activities.