1. * Institut de Physique du Globe Paris
Implementation of an observatory strategy in the Lucky Strike vent field
The MOMAR (“Monitoring the Mid-Atlantic Ridge”) project has been developed to promote a coordinated and multidisciplinary long-term study of hydrothermal environments at the Mid-Atlantic Ridge (MAR) near the Azores (35°N to 40°N).
Apologize for Javier - all mistakes are competely my own
Goal of talk: Present overview to provide background to the present status of the MOMAR project and is based on colleagues input (figures, help, information,…) during the last few years
One of the central goals of our community of ridge scientists is to understand the causal links among magmatic, tectonic, hydrothermal, biochemical and biological activities at the ridge crest, as well as the influence of these activities on the chemistry and biology of the Earth's ocean. A prerequisite is to acquire a wide set of data, including data about how a particular ridge environment changes with time. The objective of the MOMAR project is to promote international cooperation to establish long-term multidisciplinary MOnitoring on the Mid-Atlantic Ridge near the Azores. MOMAR will combine long-term monitoring of biological and physico-chemical activity at hydrothermal vents, with broader scale monitoring of tectonic, volcanic and hydrothermal processes at the ridge axis.
3.- Take advantage of this meeting to coordinate and define projects to achieve scientific goals spelled out in the I MOMAR meeting in Lisbon, October 1998 , provided a forum for discussion of both the scientific questions to be addressed, and the technology available with which to address them and begin to complete the science plan that was defined at the II MOMAR meeting.
Javier Escartin*, Pierre Marie Sarradin**, Céline Rommevaux-Jestin* & Mathilde Cannat*
* Institut de Physique du Globe Paris
** Ifremer Brest

2. Humphris and McCollum, Oceanus, 41 (2), 1998
Hydrothermal circulation at mid-ocean ridges is a fundamental process that controls the transfer of energy and matter from the interior of the Earth to the crust, hydrosphere and biosphere.
Mid-ocean ridges are environments in which tectonic plates move apart, magma migrates in the subsurface and erupts at the seafloor, seismic and aseismic deformation occurs in the host rock, and seawater-derived hydrothermal fluids circulate.
The circulation of these fluids transfers heat within the basement and from the basement to the seawater, extracts and/or deposits metal sulfides and modifies the chemistry of the overlying ocean. The same fluids support a variety of life forms, from thermophilic microorganisms in the subsurface and hot vents, to macro-organisms on the seafloor.
These processes affect the chemical, thermal and biological balance of oceanic environments, and they also provide the best modern insights into primitive earth systems which harbored, and, conceivably, initiated, life.
Humphris and McCollum, Oceanus, 41 (2), 1998

3. Ridge spreading rate & Hydrothermal Circulation:
Fast
vs.
Slow
1.- One of the main processes controlling the thermal structure and active processes at mid-ocean ridges is hydrothermalism, which has been observed at ridges of all spreading rates.
2.- Hydrothermalism also sustains ecosystems at the seafloor and therefore provides a link between the biosphere and deep-seated heat sources
3.- These processes are better understood at fast spreading ridges, as the geometry of the lithosphere, position of the magma chamber, and the observation of near-real time events have been well observed.
4.- Slow spreading ridges are poorly constrained. While many haydrothermal sites have been identified, no good geophysical images of the crust and the heat source are available. Studies are also more limited than at fast-spreading ridges, and no integrated study effort has been done to date, similar to those at the EPR or the JdF. ? ?
The MOMAR project: a contribution to understanding the causal links among magmatic, tectonic, hydrothermal, biochemical and biological processes at slow spreading ridge environments

4. The MOMAR Area Slow-spreading Mid-Atlantic Ridge (12 mm/yr half-rate)
In proximity to the Azores
36°to39°N - consists of several ridge segments: good targets for establishing integrated studies at regional scale, segment scale, and individual vent sites
So to study slospreading ridge axis processes, with particular focus on hydrothermal circulation, the MOMAR are has been identified by the scientific community, now for a few years, to coordinated projects and establish a de facto integrated study site, encompassing all disciplines, and over long periods of time.
1.- Momar are is located in the northern mid atlantic ridge,
2.- Located in close proximity to the Azores hot spot, which is slightly offset to the E of the axis
3.- MOMAR area adopts a multi-bull’s eye approach - a long portion of the ridge axis with several segments, extending from ~36° to 39°N, and immediately S of the Azores Plateau.

5. 4 known sites, 3 hydrothermal environments
MOMAR hydrothermal sites:
These sites correspond to 3 hydrothermal environments:
Peridotite hosted, at discontinuities, with high-T fluids and a magmatic heat source (Rainbow) or lower-T with serpentinization as driving mechanism (Saldanha, Menez Hom)
Basalt-hosted, magmatic heat source, at center of segment (Menez Gwen and Lucky Strike)
4 known sites, 3 hydrothermal environments
- Peridotite hosted, high T, end of segment at discontinuity - Rainbow
- Peridotite hosted, diffuse low T, end of segment - Saldanha
- Basalt-hosted, high T, center of segment - Menez Gwen and Lucky Strike

6. 4 known sites, 3 hydrothermal environments
MOMAR hydrothermal sites:
These sites correspond to 3 hydrothermal environments:
Peridotite hosted, at discontinuities, with high-T fluids and a magmatic heat source (Rainbow) or lower-T with serpentinization as driving mechanism (Saldanha, Menez Hom)
Basalt-hosted, magmatic heat source, at center of segment (Menez Gwen and Lucky Strike)
4 known sites, 3 hydrothermal environments
- Peridotite hosted, high T, end of segment at discontinuity - Rainbow
- Peridotite hosted, diffuse low T, end of segment - Saldanha
- Basalt-hosted, high T, center of segment - Menez Gwen and Lucky Strike

7. Axial rift Volcano flancs
Lucky Strike : a large hydrothermal vent field (2km/1km) at summit of rifted central volcanoe
Lucky Strike
Axial rift
Lucky
Strike
Volcano flancs
Fornari & Humphris
Lucky Strike is the selected MOMAR site for integrated & multiscale long-term monitoring of ridge hydrothermal processes and ecosystems

8. Lucky Strike : a large hydrothermal vent field (2km/1km) at summit of rifted central volcanoe
More than 40 identified high-T & low-T vents ….
A remarkable diversity of species….
A Marine Protected Area in the portuguese ZEE.
Humphris et al.

9. Vent ecosystem dynamics in the MOMAR area
Dispersal
Hydrothermal
Ecosystem
Hydrothermal
Fluxes
Propagule
input
Evénements magmatiques ou tectoniques, la nourriture n’est pas limitante, facteurs saisonniers liés à la reproduction ?, apports pélagiques, compétition intra et interspécifique pour l’espace ou la ressource, prédation, grazing…
Magmatic
Tectonic
Events
Photosynthetic
seasonal
input
Biological
Interactions
microbiology

10. Lucky Strike observatory design I 2006-2009
Light ASSEM buoy design
Time series sampling
Long term chemical monitoring
EM monitoring

11. Lucky Strike observatory design II 2009-
AUV for rapid response
Long term visual monitoring
EM monitoring

12. Lucky Strike end of site survey phase 2005-2006
Seafloor mapping and imaging
Volcanoe scale on bottom gravity survey
Segment scale seismic reflection & refraction cruise

13. EXOMAR (2005, Godfroy): Bio/ecological studies of MOMAR sites
Upcoming Cruises:
EXOMAR (2005, Godfroy): Bio/ecological studies of MOMAR sites
SISMOMAR (2005, W. Crawford): 3D seismic structure of the LS segment and central volcano:
Porosity of the segment and central volcano
Presence of fluids and heat sources
Velocity structure for microseismicity studies
GRAVILUCK (2005/2006, V. Ballu): Geodesy and seafloor gravity. Observatory design phase I (Long-term monitoring of seafloor vertical deformation and gravity)
MOMARETO (2006, Sarradin):
Ecosystem studies. Observatory design phase I (Visual and chemical monitoring of vent habitats).
Finally, additional work will be done in the area in coming months, in particular a large-scale seismic expetiments to image the lithospheric structure that will be critical to understand the distribution of porosite, provide constraints on the plumbing system and the heat sources, and give a velocity structure than can later be used for microsesmimicty studies. A geodey project is in principle funded with deployment of benchmarks.
And 2 other project, one linked to EXOCET/D for instrument deployment and testing, and another for ecological studies at different MOMAR sites, including Lucky Strike.
In addition other proposals submitted so a fair amount of field work that I think qualifies as initiation of an Integrates study in the area
We thus have a good base of data from the segment scale to the site scale for implementation of an integrated study site for long term studies, that can also serve as a basis for tempral studies, to monitor changes associated with the evolution of the system, or in response to events such as the 2001 seismic crisis.

14. Further implementation of Phase I and Phase II observatory design:
MoMAR is an international, InterRidge sponsored program with european leadership. MoMAR holds frequent workshops (last to date in Lisbon, april 2005).
It is supported by national funding agencies and marine institutes in France, the US, Portugal, the UK, with active involvment of individual scientists in other european countries.
It benefits from EC support through the STREP and MCRTN schemes. It is a component of the ESONET “european seafloor observatory network”.
MoMAR welcomes participation of interested scientists and engineers. For more information & contacts :
Finally, additional work will be done in the area in coming months, in particular a large-scale seismic expetiments to image the lithospheric structure that will be critical to understand the distribution of porosite, provide constraints on the plumbing system and the heat sources, and give a velocity structure than can later be used for microsesmimicty studies. A geodey project is in principle funded with deployment of benchmarks.
And 2 other project, one linked to EXOCET/D for instrument deployment and testing, and another for ecological studies at different MOMAR sites, including Lucky Strike.
In addition other proposals submitted so a fair amount of field work that I think qualifies as initiation of an Integrates study in the area
We thus have a good base of data from the segment scale to the site scale for implementation of an integrated study site for long term studies, that can also serve as a basis for tempral studies, to monitor changes associated with the evolution of the system, or in response to events such as the 2001 seismic crisis.