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Expedition IODP 357 – Life and serpentinization of the Atlantis Massif

An international team of 32 scientists, including 3 IPGP members, led by Gretchen Früh-Green from ETH Zurich (Switzerland) and Beth Orcutt from the Bigelow Laboratory for Ocean Sciences (USA) is taking part in the IODP 357 expedition "Atlantis Massif Serpentinization and Life".

Publication date: 01/01/2016

Research

Related themes : Origins

This programme, planned and led by the European consortium ECORD as part of the international IODP programme, aims to study the Atlantis Massif of the Mid-Atlantic Ridge by integrating the three biological, chemical and tectonic aspects. Following an oceanographic campaign on board the British ship James Cook (from October 26th to December 11th 2015), all the scientists are currently gathered in Bremen to study the cores.

Live from Bremen: signs of life identified in hydrous mantle rocks!

An initial preliminary study of an unpublished sequence of samples taken from rocks of mantle origin has enabled the international team to identify signs that could indicate the presence of active ecosystems in these rocks, which we are also trying to understand how they are unearthed from the ocean floor at slow ridges.

The Atlantis massif is an undersea mountain around 4,000 m high, located close to the Mid-Atlantic Ridge, within one of the longest mountain chains in the world, stretching from the Arctic Ocean to the South Atlantic. This massif is the result of a particular tectonic context which, unlike the other ridge massifs made up of volcanic rocks, allowed rocks from the Earth’s mantle to outcrop on the ocean floor.

These rocks are chemically and mineralogically different from most other rocks on the ocean floor. In particular, they alter in the presence of seawater, in a process called serpentinisation, which produces hydrogen, methane and heat.

It is these reactions that are of particular interest to the scientists on the expedition, as they represent a possible driving force for the appearance and development of life in the absence of light, and the conditions that prevail in these deep environments could be similar to those encountered on other planets, or at the beginning of the Earth’s history.

These bio/geo/chemical processes are also at the origin of the spectacular ‘Lost city’ underwater site, with its large white carbonate towers, up to 60 m high, formed by the emission of warm hyperalkaline water percolating through the mantle rocks. These structures also represent a deep-sea ‘oasis’ and are home to unique micro-organisms that draw their energy from the hydrogen and/or methane emitted.

 

The scientific objectives of the IODP 357 expedition

The main scientific objectives of the IODP 357 expedition to the Atlantis Massif revolve around three main themes (biological, chemical and tectonic) and will attempt to answer a number of questions, including the following:

  • What is the nature and structure of the microbial communities hosted by the serpentines and to what depth can this microbial activity take place?
  • How do these communities differ from or interact with communities in sediments or basaltic oceanic crust of the same age?
  • What are the consequences of serpentinisation processes for the major (bio)geochemical cycles?
  • How are carbon phases distributed locally and regionally? What are the rates of carbon fixation, in the form of biomass or solid carbonate, in crustal rocks during low-temperature hydrothermal activity? What role does serpentinisation play in carbon sequestration?
  • How are mantle-derived rocks exhumed from the ocean floor at slow ridges and what role do exhumation faults play in hydrothermalism and serpentinisation?

 

The programme

Nine members of the scientific team embarked with scientists and engineers from the ECORD Science Operator (ESO) on board the British ship James Cook for 6 weeks of exploration of the Atlantis Massif (from 26 October to 11 December) during the at-sea phase of the expedition. During this period, the team collected rocks from the Atlantis Massif using two types of drill, operated by the British Geological Survey (BGS, UK) and MARUM (Germany). This is the first IODP expedition to use this type of remotely operated drilling technology. Only a few initial measurements were carried out on board on the cores, as well as archiving the samples intended for microbial ecology, which are more sensitive to degradation and contamination.

All the members of the scientific team and ESO are now together for the onshore phase of the expedition, which began on 20 January at the IODP core library and MARUM laboratory in Bremen, Germany. The cores are now being fully described and sampled for various analyses, and the initial results of the expedition will be published in peer-reviewed journals and in the IODP proceedings. After a period of one year, the cores can be used by any scientist wishing to study them for further research.

 

IPGP researchers involved in the IODP 357 mission

Mathilde Cannat will be focusing on the relationship between the mantle and the magma exhumed along the Atlantis Massif. Her aim is to understand the magmatism and volcanism of the ridge during mantle exhumation.

Javier Escartin will study the outcrop zone and deformation mechanisms along faults. He will be working on the links between fluid deformation and the biosphere.

Bénédicte Ménez will seek to characterise the biological or abiotic (without the intervention of living organisms) origin of the organic carbon found in these rocks. This will provide a better understanding of the processes capable of synthesising molecules of prebiotic interest in these environments, as well as identifying the sources of carbon used by chemosynthetic ecosystems drawing their energy from the serpentinisation reaction, far from any source of light.

 

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