Mission Moho

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Understanding the Formation and Evolution of the Oceanic Lithosphere
September 7-9, 2006, Portland, Oregon, USA

An international workshop sponsored by
IODP-MI/JOI/Ridge 2000/InterRidge


 


Workshop Description


The goal of drilling a complete section through the oceanic crust and into the upper mantle has been reiterated throughout the history of scientific ocean drilling. It is highlighted in the IODP Initial Science Plan as the "21st Century Mohole" Initiative, one of eight high-priority scientific objectives.

Inherent in this goal is the need for scientific and technical growth, for a clearly defined scientific strategy, and for parallel development of essential technology and operational experience.

This workshop will develop the scientific and operational framework for Mission Moho, providing guidance for IODP's 21st Century Mohole Initiative for a decade or more. The workshop will focus on and define the "Road to Moho" by identifying the scientific and engineering objectives that can begin immediately with available technology while leading us toward the ultimate "Mohole," a complete, in situ section through ocean crust.

The workshop will be held in Portland, Oregon, September 7-9, 2006. Target attendance is 80, including a significant number of graduate students and early-career scientists and engineers.


Workshop Background

The formation and evolution of the oceanic lithosphere is a dominant process in the chemical differentiation and consequent physical modification of our planet. This evolution encompasses the transfer and transformation of material and energy from Earth's mantle to the crust and from the crust, to the ocean and atmosphere. Independent of sunlight, the evolving ocean crust supports life in unique subsurface and seafloor habitats that may resemble the earliest of Earth's ecosystems. From its formation until it returns by subduction to the mantle, the oceanic lithosphere interacts with seawater, sequesters surface materials (including water) and recycles them back into the mantle.

Mission Moho will provide an essential pathway to understand these processes. Mission Moho will encompass many branches of earth and biological sciences that are essential for understanding the formation and evolution of ocean lithosphere. The ultimate completion of a "Mohole" that penetrates a complete section of oceanic crust will be a giant step forward in our understanding of the lithosphere. But, it can only be achieved if its scientific context and geographic location are carefully chosen and thoroughly understood. Growth of our technical capabilities and operational experience is crucial to the success of the mission.

In planning for Mission Moho, workshop participants will discuss strategies for unraveling the relationships among geological, hydrological, and biological processes in the upper and lower crust and in the uppermost mantle. Strategies must combine observation, sample collection, remote and in situ data collection, and quantitative modeling studies to encompass: deep earth structure and material flow; magma formation and magma evolution; volcanic and tectonic construction at oceanic spreading centers; deep fluid circulation and fluid-rock interaction; and fluid behavior and chemical interactions at and near the seafloor. Strategies must also be developed for understanding the microbial ecosystems that may exist where fluids flow within the ocean crust. Microorganisms may mediate chemical budgets by catalyzing and deriving energy from a wide variety of geochemical reactions.


Purpose of the Workshop

Workshop participants will be challenged to redefine and prioritize the key scientific objectives and the technical and operational elements of a global drilling strategy to enhance our knowledge and understanding of the formation and evolution of the ocean lithosphere. Beginning with problems that can be addressed using current technology, they will provide a conceptual framework that prioritizes those problems and relates them to long-term IODP scientific goals.

IODP is unique in its ability to provide effective tools for direct scientific sampling and measurement in remote and hostile deep sub-seafloor environments. IODP platforms are the only tools readily available for direct scientific sampling of hard rock, consolidated sediment and fluids below the seafloor. Scientific drillholes also provide valuable access for short- and long-term sub-seafloor monitoring.

However, drillholes are spatially limited and they need to be understood in their broader context. Spatial context for ODP and IODP drillholes has primarily been provided before drilling occurs through site surveys. Workshop participants will consider ways in which IODP can pursue common objectives with other national and international programs, such as InterRidge and Ridge 2000 to enhance the overall science returns.

The outcome of the workshop will be reported in a summary article in Eos and a workshop report that will provide guidance to IODP by describing the scientific objectives and recommending a drilling strategy that includes the technical and operational requirements for Mission Moho.

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Workshop Structure and Agenda

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The workshop will alternate plenary sessions with smaller breakout activities. There will be a limited number of keynote talks and reports on recent activities and an evening poster session.

Topics for the breakout sessions will be developed by the organizing committee. Some possible areas of discussion are listed below, but this list is neither complete, nor definitive.

Applicants are encouraged to submit one page white papers outlining an important question, opinion or issue relevant to the workshop. White papers will assist the steering committee in setting the workshop agenda. They will be posted on the workshop website and distributed to all attendees.

The Road to the Moho - Scientific Questions

• Extent and modes of fluid/rock interaction in the ocean crust and upper mantle
• Hydrothermal circulation, geochemical budgets and microbial interactions
• Distribution of heat flow and aging of the oceanic lithosphere
• Nature and extent of the sub-seafloor biosphere in crustal and upper mantle rocks
• Sources of seafloor magnetization in oceanic crust and upper mantle
• Petrological nature and evolution with age of seismic layer boundaries (layer 2/3, Moho)
• Magmatic accretion processes: melt/rock interactions in the upper mantle and lower crust
• Interactions of magmatic and tectonic processes at oceanic spreading centers
• Composition and properties of the evolving oceanic plate: mass transfer from and into the deep earth

The Road to the Moho - Strategies

• Consideration of contrasting or complementary environments - variations in spreading rate, mantle temperature or tectonic setting

• Consideration of drilling into deep crustal "windows" in core complexes and other faulted exposures such as Hess Deep.
• Balancing drilling along flow line(s) with drilling along isochrons
• Balancing drilling in relatively young crust vs. older crust -- defining "drillable" young crust
• Appraisal of existing deep holes
• Appraisal of geophysical studies at existing deep-drilled sites
• Consideration of existing drilling technology (e.g., riser drilling) and of required technological developments to drill deep in oceanic crust

Relationship To InterRidge, Ridge 2000 and other programs

One goal of the workshop is to identify areas in which Mission Moho potentially intersects and enhances the goals of other major programs. For example, the US Ridge 2000 program has targeted several "Integrated Studies Sites" - focus areas for multi-disciplinary projects that develop a whole-system "mantle-to-microbe" understanding of crustal accretion. Many of the key questions on evolution of oceanic lithosphere are being addressed at such sites. The better our knowledge of present day spreading processes, the better our experimental design and future understanding of ocean crust. Similar synergies can be found with the emerging ORION observatories, the European-led Mid-Atlantic Ridge (MOMAR) observatory site, and the Korean, Japanese and US program interests in the back-arc basins of the western Pacific.

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Steering Committee

David Christie (co-chair)
University of Alaska, Fairbanks
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Benoît Ildefonse (co-chair)
CNRS/Universite Montpellier 2
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Natsue Abe
JAMSTEC
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Shoji Arai
Kanazawa University
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Wolfgang Bach
Universität Bremen
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Donna Blackman
Scripps Institution of Oceanography
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Robert Duncan
Oregon State University
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Emilie Hooft
University of Oregon
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Susan Humphris
Woods Hole Oceanographic Institution
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Jay Miller
Texas A&M University
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Travel and Logistics

[Information for participants will be posted here in mid-May] 

The workshop will be held at 5th Avenue Suites Hotel in downtown Portland, Oregon .
Portland International airport (PDX) is 40 minutes and $2.00 away by light rail.
There are direct flights to PDX from Narita, Osaka, Frankfurt and many US cities.
Portland has numerous excellent and relatively inexpensive restaurants, a diverse arts and music scene and other attractions, including its Saturday Market. The Columbia Gorge, Mt St Helens, Mt Hood and the scenic Oregon coast are all within a two-hour drive. 


Links to Earlier Planning Documents and Workshop White Papers


Workshop Deliverables