2008 Update

Ultra-slow Spreading Ridges
2008 Working Group Update

Jonathan Snow, Working Group Chair

The Ultraslow Spreading Ridges WG has been quietly active over the past few years. The membership of the WG has been informal, including Jon Snow, Eric Hellebrand, Henry Dick and Peter Michael (all USA), Wilfried Jokat (Germany), and several others.
The community has made progress in the arctic ridges, the Southwest Indian Ridge, and other localities. Some of the highlights of research activities include, but not limited to, the following:

Research Cruises:
- Chinese cruise to the SWIR in 2007 that found the first ultra-slow black smoker system on the Southwest Indian Ridge (see: http://www.interridge.org/node/86 )
- Norwegian cruise in 2008 found the first high-temperature system on the Knipovich Ridge (see: http://www.interridge.org/node/5581 )
- Japanese cruise to the Southwest Indian Ridge near the Marion hotspot in January 2008 (see: http://www.interridge.org/node/5452 )
- USA and UK funding to study the Mid-Cayman Spreading Center in 2009 and 2010, respectively.

- IODP continental breakup symposium: Working group on arctic margins, Pontresina, Switzerland, 2006.
- Polar Ridges Meeting and Workshop, Sestri Levante, Italy, 2006.
- AGU Fall Meeting: V12-C, I-II-III (posters) “Tectonics, Petrology, and Geochemistry of Ultraslow Spreading Ridges: Recent Advances”, 2006.
- AGU Fall Meeting: Multiple presentations in session “Bringing Together Observations and Models at Rifted Margins and Extensional Basins”, 2007.
- International Lherzolite Conference, presentations by Dick, Snow, Hellebrand, von der Handt on Gakkel Ridge mantle dynamics, 2008.
- Geological Society of America, presentations by Snow and Dick on ultraslow spreading and continental breakup, 2008.
- AGU Fall Meeting: T05 “Magmatic, Tectonic, and Hydrothermal Interactions at (Ultra-) Slow Spreading Mid-Ocean Ridges,” and T07 “Evolution of Magma-Starved Rifts in Oceans, Continents and Backarcs”, 2008.

Selected Papers:
- Liu, et al. (2008) Ancient, highly heterogeneous mantle beneath Gakkel ridge, Arctic Ocean. Nature 452: 311-316.
- Goldstein, et al. (2008) Origin of a “Southern Hemisphere” geochemical signature in the Arctic upper mantle. Nature 453: 89-93.
- Sohn, et al. (2008) Explosive volcanism on the ultraslow Gakkel ridge, Arctic Ocean. Nature 453: 1236-1238.

The Ultraslow Spreading Ridges WG was formed as a merger of the Arctic and SW Indian Ridge WGs in 2004 as part of the InterRidge Next Decade Plan. Our objective at that time was to convene an international workshop on ultraslow spreading ridges, which we successfully held in 2006 in Sestri Levante, Italy, as listed above. Following the rules for IR WGs as described in the 2006 InterRidge News, our work is completed, and it is now time to disband the WG.

Note: At the IR Steering Committee meeting in October 2008, the decision to disband the WG in its current form was agreed upon, but it was noted that the Steering Committee would also welcome future proposals to develop a new WG on this theme at any time in the future.