Pourquoi pas? HERMINE (GApr07)

Cruise plan

Cruise Info. 
Ship name (ship code)Pourquoi pas? (35PK)
Cruise identifierHERMINE (GApr07)
Cruise period2017-03-16 — 2017-04-27
Port of departureMindelo, Cape Verde
Port of returnPonta Delgada, Portugal
ObjectivesThe hydrothermal activity along mid-ocean ridges is a fundamental process controlling the exchanges of heat and chemical species between the oceanic crust and seawater. Hydrothermal vents can serve as sources or sinks for many trace elements in the ocean. It has long been thought that Fe and other trace metals, which play a key role in the primary productivity of many regions in the oceans, were mostly removed in the vicinity of the vents, being incorporated into oxy-hydroxide or sulfide minerals, and thus not exported into the deep ocean. However, recent studies showed that Fe can be stabilized in hydrothermal plumes and transported, together with other trace metals, far across the ocean, up to thousands kilometers away from the vent source. However, little is known so far on the processes occurring from the fluid exit to the distal far-field non-buoyant plume, particularly in regions where seafloor massive sulfide (SMS) deposits are observed, such as at the vicinity of slow-spreading ridges and back-arc basins.

The objectives of this GEOTRACES process study are:
1. What are the concentrations of metals, their physical (particulate/dissolved) and chemical (redox/organic/inorganic) speciation within the plume?
2. What role do biogeochemical processes play in controlling trace element and gas distribution in hydrothermal plumes? What are the dispersal and biogeochemical reactivity of these elements?
3. Can we establish a reliable baseline for the actual hydrothermal plume functioning, using a multiscale chemical and microbial mapping of hydrothermal plumes in order to further assess the potential impact of seabed mining?

Chief scientistIves Fouquet (IFREMER, Brest)
ProjectGEOTRACES -Trace elements and their isotopes in the water column
Ocean/sea areas 
GeneralNorth West Atlantic Ocean (limit 40W)
SpecificMid Atlantic Ridge, TAG and Snake Pit sites (21-26°N/44.5-46.5°W)