Emission and plume transport of methane and hydrogen from the Mid-Atlantic Ridge

• Antragsteller: Dr. Robin Keir; Dr. Oliver Schmale
• Fachliche Zuordnung: Mineralogie, Petrologie und Geochemie
• Förderung: Förderung von 2003 bis 2010
• Projektkennung: Deutsche Forschungsgemeinschaft (DFG) - Projektnummer 5415833

Methane is emitted at mid-ocean ridges by hydrothermal venting and, in slow spreading centers, by serpentinization of ultramafic rocks. The latter process is indicated by observations on the mid-ocean ridge in the North Atlantic, where methane plumes emanate from ultramafic outcrops on the sidewalls of the rift valley. These plumes contain little of the ³He and Mn anomalies that are typically associated with hydrothermal venting. The relative contribution of the mid-ocean ridge sources to the inventory of methane in the deep sea is not known; especially unclear is the amount of methane that may be generated by serpentinization. The methane produced by either of these processes within the ridge probably contains a heavy 13C/12C isotopic ratio, which leaves a signature of the mid-ocean source. As part of the SPP, we propose to investigate the input of methane to the ocean at the Mid-Atlantic Ridge between 2° and 11°S, which is a region that until now has not been explored for hydrothermal activity. In addition we will measure the activity of Rn²²² in order to estimate the methane oxidation rate. Water samples takem from the CTD/Rosette collectors will be degassed and analyzed on board for dissolved methane by gas chromatography. The remainder of the gas sample will be returned to GEOMAR and subsequently analyzed for the 13C/12C ratio of methane by in-line ratio monitoring mass spectrometry.

• DFG-Verfahren: Schwerpunktprogramme
• Teilprojekt zu: SPP 1144: Vom Mantel zum Ozean: Energie-, Stoff- und Lebenszyklen an Spreizungsachsen
• Beteiligte Person: Professor Dr. Gregor Rehder