Different TDM/CH4 hydrothermal plume signatures: TAG site at 26N and serpentinized ultrabasic diapir at 15 degrees 05'N on the Mid-Atlantic ridge

Journal Article · Fri Nov 01 04:00:00 EST 1991 · Geochimica et Cosmochimica Acta; (United States)

DOI:https://doi.org/10.1016/0016-7037(91)90484-M· OSTI ID:5247928

Charlou, J L; Bougault, H ^[1]; Appriou, P ^[2]; Nelsen, T; Rona, P ^[3]

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1. IFREMER Centre de Brest, Plouzane (France)
2. Univ. de Bretagne Occidentale, Brest (France)
3. NOAA-AOML-OCD, Miami, FL (United States)

As a part of the 1988 NOAA VENTS Program, CH{sub 4} and Mn tracers were used to identify and compare hydrothermal plumes found above the TAG Field (26{degrees}N) and in the rift valley at 15{degrees}N close to the eastern intersection of the ridge axis with the 15{degrees}20'N Fracture Zone at the Mid-Atlantic Ridge (MAR). Active hydrothermal venting was confirmed at TAG, based on elevated concentrations of total dissolved Mn (TDM up to 30 nmol/kg), high CH{sub 4} concentrations (up to 200 nL/L), and elevated nephelometry signals. Plumes of a different composition were identified at 15{degree}N with high CH{sub 4} concentrations (up to 400 nL/L), low total dissolved Mn concentrations (TDM < 1 nmol/kg) and no significant nephelometry signal. The different properties of these tracers and the different tracer ratios can be used to deduce vent fluid characteristics and compare one hydrothermal area to another. TDM/CH{sub 4} and Nephel/CH{sub 4} ratios at TEG are of the same order of magnitude as those observed at other spreading axis hydrothermal fields. At 15{degrees}N, the low TDM/CH{sub 4} ratio provides evidence of fluid circulation into ultrabasic rocks and offers a potentially useful and single method of exploring for hydrothermal activity associated with serpentinization. Mantle degassing through hydrothermal activity associated with serpentinization is an important process with respect to chemical and thermal exchanges between the upper mantle and the ocean. Different ratios of hydrothermal tracers (i.e., TDM/CH{sub 4}) provide a useful framework for identifying subseafloor processes along mid-oceanic ridges.

• OSTI ID: 5247928
• Journal Information: Geochimica et Cosmochimica Acta; (United States), Journal Name: Geochimica et Cosmochimica Acta; (United States) Vol. 55:11; ISSN GCACA; ISSN 0016-7037
• Country of Publication: United States
• Language: English

Related Subjects

15 GEOTHERMAL ENERGY
152001* -- Geothermal Data &amp; Theory-- Properties of Aqueous Solutions
58 GEOSCIENCES
580000 -- Geosciences
ALKANES
CHEMICAL COMPOSITION
DEGASSING
EARTH MANTLE
ELEMENTS
FLUIDS
FUMAROLES
FUMAROLIC FLUIDS
GEOCHEMICAL SURVEYS
GEOTHERMAL FLUIDS
GEOTHERMAL SYSTEMS
HYDROCARBONS
HYDROTHERMAL SYSTEMS
ISOTOPE APPLICATIONS
MANGANESE
METALS
METHANE
MID-ATLANTIC RIDGE
MINERALS
ORGANIC COMPOUNDS
PLUMES
SERPENTINE
SILICATE MINERALS
SURVEYS
TRACER TECHNIQUES
TRANSITION ELEMENTS