FN Archimer Export Format
PT J
TI Evidence for methane isotopic bond re-ordering in gas reservoirs sourcing cold seeps from the Sea of Marmara
BT 
AF Giunta, Thomas
   Labidi, J.
   Kohl, I.E.
   Ruffine, Livio
   Donval, Jean-Pierre
   Géli, Louis
   Çağatay, M.N.
   Lu, H.
   Young, E.D.
AS 1:1,2;2:3,4;3:4;4:1;5:1;6:1;7:5;8:6;9:4;
FF 1:;2:;3:;4:PDG-REM-GM-LCG;5:PDG-REM-GM-LCG;6:PDG-REM-GM-LAD;7:;8:;9:;
C1 IFREMER, Unité des Géosciences Marines, 29280 Plouzané, France
   Université de Bretagne Occidentale, Laboratoire Géosciences Océan, 29280 Plouzané, France
   Université de Paris, Institut de Physique du Globe de Paris, CNRS, F-75005 Paris, France
   University of California Los Angeles, Department of Earth, Planetary and Space Sciences, CA 90095, Los Angeles, USA
   Istanbul Teknik University, Faculty of Mines, Department of Geological Engineering, TR-34469 Istanbul, Turkey
   Peking University, Department of Energy & Sciences, College of Engineering, Beijing 100871, China
C2 IFREMER, FRANCE
   UBO, FRANCE
   UNIV PARIS, FRANCE
   UNIV CALIF LOS ANGELES, USA
   UNIV TECH ISTANBUL, TURKEY
   UNIV PEKING, CHINA
SI BREST
SE PDG-REM-GM-LCG
   PDG-REM-GM-LAD
UM LGO
IN WOS Ifremer UPR
   copubli-france
   copubli-univ-france
   copubli-int-hors-europe
   copubli-sud
IF 5.785
TC 24
UR https://archimer.ifremer.fr/doc/00653/76556/77851.pdf
LA English
DT Article
CR MARSITECRUISE
BO Pourquoi pas ?
DE ;cold seeps;methane;clumped isotopologues;bond-ordering
AB The measurement of methane clumped isotopologues ( and ) allows exploring isotope bond ordering within methane molecules, and may reveal equilibrium temperatures. Whether such temperature reflects the formation or re-equilibration temperature of the methane is not well understood, but would have critical implications for the use of methane clumped isotopologues as geo-thermometers. Here we investigate gas bubbles from vigorous emissions at cold seeps (n = 14) in the Sea of Marmara, Turkey. These cold seeps are sourced from deeper sedimentary reservoirs. Conventional geochemical tracers such as carbon and hydrogen bulk isotopic ratios (13C/12C and D/H) or n-alkane molecular ratios, suggest these gases reflect various degrees of mixing between thermogenic and microbial sources. Some samples would generally be considered purely microbial in origin (; ‰). We report measurements of and showing that a fraction of those gases are in internal thermodynamic equilibrium, with the abundances of the two mass-18 isotopologues indicating concordant temperatures of ∼90 °C and ∼130 °C. These concordant temperatures are recorded by gases of putative microbial and thermogenic origin; the temperatures of equilibration are irrespective of the formation mechanism of the gases. We conclude that the two high-temperatures recorded by and are best explained by non-enzymatic re-equilibration at two local subsurface temperatures. First principles suggest that unequal rates of exchange are possible. Disequilibrium signatures where the two isotopologues yield discordant apparent temperatures are exhibited by other samples. In those cases the data define a trend of variable at nearly constant . These signatures are enigmatic, and we investigate and reject multiple possible explanations including mixing, diffusion or Anaerobic Oxidation of Methane. Different rates of re-equilibration between the two rare isotopologues are implied, although lacks experimental foundation at present. In general, all of these data point towards re-equilibration of the mass-18 methane isotopologues as an important process. 
PY 2021
PD JAN
SO Earth And Planetary Science Letters
SN 0012-821X
PU Elsevier BV
VL 553
UT 000593204200008
DI 10.1016/j.epsl.2020.116619
ID 76556
ER

EF