Gas hydrates from the Sea of Marmara : Variability in composition and origin of the hydrate-forming gases L. Ruffine1*, J. P. Donval1, J. L. Charlou1, L. Geli1, P. Henry2, G. Etiope3 1 Département Géosciences Marines, IFREMER Centre de Brest, Plouzané, Cedex 29 280, France. 2 CEREGE / Collège de France, 13545 Aix en Provence, France 3 Istituto Nazionale di Geofisica e Vulcanologia Sezione Roma 2, * Corresponding author