Intense CH{sub 4} plumes generated by serpentinization of ultramafic rocks at the intersection of the 15{degree}20[minutes]N fracture zone and the Mid-Atlantic Ridge

Journal Article · Wed Jul 01 04:00:00 EDT 1998 · Geochimica et Cosmochimica Acta

DOI:https://doi.org/10.1016/S0016-7037(98)00138-0· OSTI ID:655493

Charlou, J L; Fouquet, Y; Bougault, H; Donval, J P; Etoubleau, J ^[1]; Jean-Baptiste, P; Dapoigny, A ^[2]; Appriou, P ^[3]; Rona, P A ^[4]

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1. IFREMER Centre de Brest, Plouzane (France). Dept. Geosciences Marines
2. CEA Saclay, Gif-sur-Yvette (France)
3. Univ. de Bretagne Occidentale, Brest (France)
4. Rutgers-the State Univ. of New Jersey, New Brunswick, NJ (United States)

As part of the FARA French-US Program designed to study the Mid-Atlantic Ridge (MAR) between 15{degree}N and the Azores, twenty-three dives with the submersible Nautile were conducted during the French-US Faranaut 15N cruise on the eastern and western parts of the Fracture Zone/Ridge axis intersection. South of the eastern ridge-transform fault intersection, nine Nautile dives were made within the rift valley and along the western rift valley wall. CH{sub 4} concentrations in the bottom waters reach 53.2 nmol/kg along faulted zones on top and on the east flank of the ultramafic inner corner high where serpentinized rocks outcrop. No {sup 3}He anomaly is associated with methane, ruling out any primary mantle component. High CH{sub 4} anomalies (up to 22 nmol/kg) are also present in the bottom waters of the rift valley northern segment on both the western and eastern valley walls and on the inner high adjacent to the eastern wall where ultramafic rocks outcrop. Seven vertical hydrocasts carried out in the axial valley (4500 M deep) show an intense CH{sub 4} anomaly, with a maximum (35.8 nmol/kg) at 3200 m depth. CH{sub 4} concentrations of 9.9--14.9 nmol/kg are also present on the western wall along the 3200 m isobath. CH{sub 4} output from ultramafic outcrops on the western and eastern intersections of the Fracture Zone with the MAR is believed to reflect ongoing serpentinization.

• OSTI ID: 655493
• Journal Information: Geochimica et Cosmochimica Acta, Journal Name: Geochimica et Cosmochimica Acta Journal Issue: 13 Vol. 62; ISSN GCACAK; ISSN 0016-7037
• Country of Publication: United States
• Language: English

Related Subjects

03 NATURAL GAS
58 GEOSCIENCES
METHANE
MID-ATLANTIC RIDGE
MINERALIZATION
NATURAL GAS DEPOSITS
ORIGIN
SEEPS
SERPENTINITES