Mission Serpentine

The cruise will occur from February 26th until April 6th 2007 on the Mid-Atlantic Ridge (MAR), offshore from South America and Africa at about the same latitude than Kingston, Jamaica and Dakar, Sénégal.
More scientifically between 13° and 17°N on board of the Pourquoi pas ?. This cruise is one of the results of a 30 year-old French-Russian scientific collaboration. The multidisciplinary aspect of the cruise has to be noted. Geochemistry, Geology, biology and microbiology are indeed all highly represented on board !

Global aim

It consist of the study of diversity, as well as the biological and geological interactions within deep ultramafic hydrothermal systems. Achadze (4000m) is one of these sites and the deepest on earth known up until now.

The project aims at analysing the impact of tectonics (the ridge spreads out at a rate of 2cm/year) on hydrothermal processes.

Multidisciplinary studies on the same samples will focus on understanding the interactions among fluids, bacteria, mineral and animals.

A bit of a geology lesson now! 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.

In the absence of volcanism, outcrops of mantle rocks occur on the slow spreading ridges (spreading out < 2 cm/year). Considering the high pressure and the presence of cracks, seawater permeates the mantle. A change in the temperature drives a circulation pattern within the mantle, which leads to intense reactions with non-hydrated minerals.

One of the goals of Serpentine is t o study these reactions that have impacts in various fields like geology, geochemistry, biology and microbiology.

Research themes

They are numerous and deal with life science as much as with geosciences.

- Study of hydration processes and chemical exchanges between ocean and mantle. Hydrogen is of extremely high concentration in the fluids and is at the root of hydrocarbons and prebiotic molecules production. These phenomena revive the interest for ultramafic hydrothermal systems as origin of life location.

- Study of metallogenic aspects (deposit formation). The sulphur deposits, like in the 16°38’ zone, are very rich in copper, zinc, cobalt, silver and gold. This kind of deposit is hardly known on terrestrial fossil ores.

- Biological studies on the biodiversity and the specificity of hydrothermal populations (worms, corals, shrimps, mussels…).

- Microbiology of piezzophilic bacteria, plasmids and viruses. They all play an important role in biogeochemical cycles.

- Bathymetry and gravimetric measures. Very little data is available for these zones. The “en route” measurement module of Victor 6000 will enable a detailed mapping of the hydrothermal sites.