Media release

Serpentine scientific cruise: discovering the diversity of geological and biological processes on the Mid-Atlatic Ridge (MAR)

Paris, february 21

On February the 26th a French-Russian scientific team will board the French R/V Pourquoi pas? and explore during 6 weeks 3 ultramafic hydrothermal systems on the MAR. The highlight of the cruise is the first time ever sampling of Achadze, the deepest vent worldwide. The Remote Operated Vehicle (ROV) Victor 6000 will carry out the sampling.
Yves Fouquet, chief scientist, is responsible for the multidisciplinary program "studies of deep sea extreme environments" (GEODE) and head of the geochemistry and metallogeny laboratory at Ifremer, Brest, France. The cruise will gather geologists, geochemists, biologists and microbiologists.

Why Serpentine for a name?

Geologically speaking, the mantle is the layer located between the core and the terrestrial crust. It is also the upper part of the lithosphere, which forms the group of tectonic plates. It is usually coated by the continental crust (couple of decades kilometres thick) or by the volcanic oceanic crust (couple of km).

The oceanic ridges are borders between plates moving away from each other. As such the MAR spreads out at a rate of 2 cm/year. This eventually leads to the formation of new sea floor. Researchers will focus on studying non-volcanic zones of the ridge during the serpentine cruise. These areas are indeed unique places where the mantle outcrops. Seawater permeates the mantle through cracks there. A change in the temperature drives a circulation pattern within the mantle, which leads to intense reactions with non-hydrated minerals. These underwater areas hold a major role in the matter and heat exchanges ocean/Earth.

The serpentine or serpentinite is a type of rock that results of the alteration of peridotites (major part of the mantle) by water and heat. The cruise has thus been named after this rock that stands in the heart of processes occurring in ultramafic-hosted hydrothermal vents.

Research interests: from rock to life…

The research themes are various and deal with life sciences as much as geosciences. The aim of the cruise is indeed the study of diversity as well as biological and geological interactions in ultramafic-hosted hydrothermal systems of the deep sea.

One of the fundamental aim of Serpentine is to better understand hydration processes and chemical exchanges between the ocean and the Earth mantle.

Previous cruises enable the team of the geochemistry and metallogeny laboratory from Ifremer, Brest, France to be the first to show that hydrogen is a product of mantle hydration. Its concentration in the fluids is high counting for about 40% of the total gas content. Besides hydrogen and carbon are the fundamental building blocks in the synthesis of organic (living) molecules from minerals, especially hydrocarbons and prebiotic molecules. These phenomena revive the interest for ultramafic-hosted hydrothermal systems as likely places for the origin of life location. Furthermore organic molecules as well as hydrogen can be used as energy source for bacterial communities. That is the reason why the study of fluids/minerals/bacteria/animals interactions will hold a major place in the Serpentine cruise.

Elsewhere, another focus will be on the formation of multimetallic sulphur mounts by hydrothermal vents. These sulphur deposits are the richest of the oceans in valuable metals (Cobalt, Copper, Silver, Gold, Zinc…). This kind of deposit is hardly known on terrestrial fossil ores.

Specialists in biology of deep environments will be on board of the Pourquoi pas? in order to study the biodiversity and the specificity of the fauna of ultramafic-hosted hydrothermal vents (worms, shrimps, clams, mussels…). Microbiologists will look at so-called piezzophil bacteria (i.e. adjust to high pressure environment), plasmids, viruses and other microorganism living under these high pressures. These organisms raise a particular interest as they play a key role in biogeochemical cycles.

Finally, bathymetric and magnetism studies will be carried out to obtain more data on the zones that are still barely known. The "en route" measurement module of Victor 6000 will enable a detailed mapping of the hydrothermal sites. This will also lead to explanations on the relationship of hydrothermal activity with cracks formation due to the opening of the Atlantic Ocean.

Serpentine: strategy issues

The exploration and access to the deep ocean are true scientific and technological challenges. Scientifical, economical and geopolitical issues have raised more and more importance over the past few years. Energy and mineral resources have indeed been spotted. Moreover it becomes compulsory to keep on going the listing of the biodiversity. France, the United-States, Japan and Russia are leading in terms of knowledge and exploration of the deep sea, but the future is uncertain since China, South Corea and India are getting heavily involved. Thanks to the French-Russian cooperation and the Serpentine cruise, France and Russia should be able to keep their number one rank in the world as far as knowledge on hydrothermal processes along the MAR are concerned.

France-Russia: more than 35 years of scientific collaboration

The first oceanographic cooperation program between France and Russia started in 1969 and included a field trip. This geosciences project was a milestone in the fruitful exchanges and group program between URSS, later Russia, and France.

The R/V Professor Logatchev had a stopover in Brest in 2004 to give evidence of this old and still active collaboration between the two countries.

For 35 years, the aim of this collaboration has been to better understand the deep ocean as well as the ocean/mantle relations, to count out potential mineral resources and to understand the ecology of hydrothermal systems mineral resources and a preservation of the environment.

Studied areas during Serpentine

Three ultramafic-hosted hydrothermal zones will be looked at. These sites were discovered a couple of years ago only! And two of them haven’t been sampled by a submersible yet! There are hardly any data about them.

Achadze
Its own particularity is to be the deepest (4100m) hydrothermal system in the world known so far. Ultramafic rocks and animals are present at this active site.

Logatchev
This vent is located at 2970m depth. Its mineral composition is very similar to the one of the Rainbow site. Animals live there but the area is inactive.

Krasnov
It spreads out from 15° to 17°N. The whole area is covered with continuous hydrothermal vents, which consist of sulphur mounts at 3700 to 3900m depth.
It is the largest sulphur deposit known in the Atlantic Ocean. It seems to be off and in a process of splitting into two. If this is right, a natural geological cut will appear. This will enable sampling of the third dimension of the hydrothermal deposit. This site will help to understand the future of hydrothermal deposit and of the biological activity when the activity stops! No studies have been carried out on this topic.