FN Archimer Export Format
PT J
TI Methane thermometry in deep-sea hydrothermal systems: evidence for re-ordering of doubly-substituted isotopologues during fluid cooling
BT 
AF Labidi, J.
   Young, E.D.
   Giunta, Thomas
   Kohl, I.E.
   Seewald, J.
   Tang, H.
   Lilley, M.D.
   Früh-Green, G.L.
AS 1:1,2;2:1;3:3,4;4:1,5;5:6;6:1;7:7;8:8;
FF 1:;2:;3:;4:;5:;6:;7:;8:;
C1 Department of Earth, Planetary, and Space Sciences, UCLA, Los Angeles, CA, USA
   Université de Paris, Institut de physique du globe de Paris, CNRS, Paris, France
   IFREMER, Unité des Géosciences Marines, 29280 Plouzané, France
   Université de Bretagne Occidentale, Laboratoire Géosciences Océan, 29280 Plouzané, France
   Thermo Fisher Scientific, Bremen, Germany
   Marine Chemistry and Geochemistry Department, Woods Hole Oceanographic Institution, Woods Hole, MA, USA
   School of Oceanography, University of Washington, Seattle USA
   Department of Earth Sciences, Eidgenössische Technische Hochschule Zurich (ETH-Z), Zurich, Switzerland
C2 UNIV CALIF LOS ANGELES, USA
   IPGP, FRANCE
   IFREMER, FRANCE
   UBO, FRANCE
   THERMO FISHER SCIENTIFIC, GERMANY
   WHOI, USA
   UNIV WASHINGTON, USA
   ETH ZURICH, SWITZERLAND
SI BREST
SE PDG-REM-GM-LCG
UM LGO
IN WOS Ifremer UPR
   copubli-france
   copubli-europe
   copubli-univ-france
   copubli-int-hors-europe
IF 5.01
TC 35
UR https://archimer.ifremer.fr/doc/00643/75521/76402.pdf
LA English
DT Article
DE ;Abiotic methane;Doubly-substituted isotopologues;High-resolution mass spectrometry;Hydrothermalism;Black smokers
AB Deep-sea hydrothermal fluids are often enriched in carbon dioxide, methane, and hydrogen. Methane effuses from metal-rich black smokers such as the Rainbow hydrothermal field, at temperatures higher than 200 °C. At the Lost City field, CH4 emanates from alkaline fluids at < 100 °C. The abundance of the rare, mass-18 CH4 isotopologues, 13CH3D and 12CH2D2, can mitigate degeneracies in the conventional isotopic signatures of methane. We studied the isotopologue compositions of methane from the Rainbow, Lucky Strike, Von Damm, and Lost City hydrothermal fields. At Rainbow, where the vented fluids are at ∼360°C, our coupled Δ12CH2D2 - Δ13CH3D data establish that methane is in internal equilibrium at °C. This may track the formation temperature of abiotic methane, or it may be the result of equilibration of methane isotopologues within the carrier fluid. Lucky Strike and Von Damm have fluid temperatures < 300°C and although Δ13CH3D values are indistinguishable from those at Rainbow, 12CH2D2 abundances are marginally higher. At Lost City, Δ13CH3D data show a range of values, which at face value correspond to apparent temperatures of between °C and °C, far hotter than fluid temperatures. A unique aspect of the Lost City data is the range of large 12CH2D2 excesses. The Δ12CH2D2 data correspond to temperatures of between °C and °C, showing a near-perfect match with fluid temperatures. We find that mixing scenarios involving microbial methane may not account for all of the isotope data. We suggest that Δ12CH2D2 values, unlike Δ13CH3D values, are prone to near-complete re-equilibration at host fluid temperatures. We suggest that 13CH3D isotopologue data are consistent with abiotic methane being synthesized at ∼350 °C. On the other hand, 12CH2D2 isotopologue ordering records post formation residence temperatures. We explore a possible mechanism decoupling the re-equilibration systematics of the doubly-substituted isotopologues. 
PY 2020
PD NOV
SO Geochimica Et Cosmochimica Acta
SN 0016-7037
PU Elsevier BV
VL 288
UT 000574843100002
BP 248
EP 261
DI 10.1016/j.gca.2020.08.013
ID 75521
ER

EF