Sestri Levante, Italy
19-22 September 2006
Workshop Report
By Jonathan Snow, Henry Dick, Elisabetta Rampone, Colin Devey
In recent years, Polar mid-ocean ridges have been the focus of some of the most exciting scientific results from mid-ocean ridges globally. 60 scientists from the international mid-ocean ridge community met in the Italian coastal town of Sestri Levante for four days in mid-September, 2006 to discuss the progress and future of research on polar mid-ocean ridges. These include the trans-Arctic Gakkel Ridge and the circum-Antarctic SW Indian and American-Antarctic ridges. These mid-ocean ridges belong primarily to the ultraslow class of mid-ocean ridges (<16 mm/yr full spreading rate). Ultraslow ridges have gained increased recognition in recent years because of the very successful exploration of the Arctic ridge system by a number of cruises since the drafting of the InterRidge Arctic Mapping and Sampling Plan in 1998 (ref). Since then, we have seen the first intentional hard rock sampling in pack ice (Jokat, 1999; Snow, 2001), mapping by submarine beneath the arctic ice (Edwards 1999) an extensive program of mapping and sampling on Gakkel Ridge (Michael, 2003; Jokat; 2003; Edmonds 2003), and on Lena Trough (Snow, 2006).
The venue turned out to be unexpectedly germane to the discussion of the geology and geophysics of mid-ocean ridges. Situated on ocean crust that had once formed part of the nonvolcanic rifted margin of the ancient Tethys ocean, the hills surrounding the conference are constructed of just the same type of rocks that make up much of the crust of the ultraslow spreading ridges. Through the presentations by Italian, French and Swiss participants new to mid-ocean ridges per se, it became clear during the meeting that the western Alpine Tethyan ophiolites form a powerful analog for the study of mid-ocean ridge spreading under conditions of magmatic starvation (Piccardo, Rampone refs Betta: what are the best ones here?). The western Tethyan ophiolites are a particularly good example of such rocks, and warrant further investigation and comparison in the future course of mid-ocean ridge studies.
A second convergence of thought and action came between the global mid-ocean ridge community and the community of scientists studying rifted margins. The Internaitonal Ocean Drilling Program scheduled a conference at nearly the same time in the Swiss Alpine town of Pontresina (an easy half-day drive away) to carry out a similar discussion for their scientific program – with a little hasty rescheduling, the two conferences took place back to back over the course of 10 days. Scientifically, the study of continental margins, particularly the non-volcanic ones, has converged to a surprising extent with the ultraslow mid-ocean ridge community. This is because the tectonics of late nonvolcanic continental rifting have a very similar constellation of geodynamic forcing functions (e.g. spreading rate, thermal structure).
Scientists at the conference presented some of their newer research stemming from the exploration of ultraslow spreading ridges. Particularly exciting new work was presented by Steven Goldstein, of the Lamont Doherty Earth Observatory, Chuanzhou Liu of the Max-Planck Institute for Chemistry in Mainz, and Sergei Silantiev, of the Vernadsky institute of Geochemistry, Russia. The common theme of these talks was the unusually continental nature of the magmatic, and tectonic processes of accretion along the Gakkel Ridge, something that had never before been suggested for a major mid-ocean ridge. Of particular interest to many in the seagoing ridge community was the detail with which tectonic and magmatic structures in ophiolites that were previously considered “dismembering” features during obduction have proven to be sea floor features with a direct relationship to magma starved rifting and tectonics (Gianreto Manatschal, Strasbourg; Francoise Chalot-Prat Nancy, Elisabetta Rampone, Genova)
In the workshop part of the meeting, delegates from 7 countries (Japan, Germany, Korea, France, Britain, China, Italy, and the US) discussed recent developments in polar ridge research in their countries and plans for the immediate future. Heartening developments include the plans in both China and Korea for increased participation in ultraslow and in particular polar mid-ocean ridge research, and the development of a new Autonomous Underwater Vehicle (AUV) by the US for mapping and sampling beneath ice, which is to be tested next summer. Another is the idea that a program similar to the SCICEX program may be in the offing. Somewhat discouraging is the sudden halt in activity on USCGC Healy due to a tragic accident this summer.
New programs that are evolving include detailed observations in several areas, including the SWIR and Gakkel Ridges, where general survey has already been completed. There is a strong sense that a further mapping and sampling survey of the Eastern Gakkel between the end of the AMORE 2001 program and the Siberian shelf edge. This survey may require a different set of techniques and competences and face a new set of challenges than previous legs. A planning meeting to discuss implementation of an international Eastern Gakkel Program is panned for early 2007 in Woods Hole.
