Modelling the Lost City hydrothermal field: influence of topography and permeability structure

Article English OPEN
Titarenko, SS ; McCaig, AM (2016)
  • Publisher: Wiley

The Lost City hydrothermal field (LCHF) is hosted in serpentinite at the crest of the Atlantis Massif, an oceanic core complex close to the mid-Atlantic Ridge. It is remarkable for its longevity and for venting low-temperature (40–91°C) alkaline fluids rich in hydrogen and methane. IODP Hole U1309D, 5 km north of the LCHF, penetrated 1415 m of gabbroic rocks and contains a near-conductive thermal gradient close to 100°C/km. This is remarkable so close to an active hydrothermal field. We present hydrothermal modelling using a topographic profile through the vent field and IODP site U1309. Long-lived circulation with vent temperatures similar to the LCHF can be sustained at moderate permeabilities of 10e-14 to 10e-15 m2 with a basal heatflow of 0.22 W m2. Seafloor topography is an important control, with vents tending to form and remain in higher topography. Models with a uniform permeability throughout the Massif cannot simultaneously maintain circulation at the LCHF and the near-conductive gradient in the borehole, where permeabilities <10e-16 m2 are required. A steeply dipping permeability discontinuity between the LCHF and the drill hole is required to stabilize venting at the summit of the massif by creating a lateral conductive boundary layer. The discontinuity needs to be close to the vent site, supporting previous inferences that high permeability is most likely produced by faulting related to the transform fault. Rapid increases in modelled fluid temperatures with depth beneath the vent agree with previous estimates of reaction temperature based on geochemical modelling.
  • References (61)
    61 references, page 1 of 7

    Allen DE, Seyfried WE (2004) Serpentinization and heat generation: constraints from Lost City and rainbow hydrothermal systems. Geochimica et Cosmochimica Acta, 68, 1347-54.

    Anderko A, Pitzer KS (1993) Equation-of-state representation of phase-equilibria and volumetric properties of the system NaClH2O above 573 K. Geochimica et Cosmochimica Acta, 57, 1657-80.

    Anderson BW, Coogan LA, Gillis KM (2012) The role of outcrop-to-outcrop fluid flow in off-axis oceanic hydrothermal systems under abyssal sedimentation conditions. Journal of Geophysical Research-Solid Earth, 117, B05103.

    Becker K (1991) In-situ bulk permeability of oceanic gabbros in Hole 735B, ODP Leg 118. Proc., scientific results, ODP, Leg 118, fracture zone drilling on the Southwest Indian Ridge, 333-47.

    Becker K, Sakai H, Adamson AC, Alexandrovich J, Alt JC, Anderson RN, Bideau D, Gable R, Herzig PM, Houghton S, Ishizuka H, Kawahata H, Kinoshita H, Langseth MG, Lovell MA, Malpas J, Masuda H, Merrill RB, Morin RH, Mottl MJ, Pariso JE, Pezard P, Phillips J, Sparks J, Uhlig S (1989) Drilling deep into young oceanic crust, Hole 504b, Costa Rica Rift. Reviews of Geophysics, 27, 79-102.

    Blackman DK, Cann JR, Janssen B, Smith DK (1998) Origin of extensional core complexes: evidence from the Mid-Atlantic Ridge at Atlantis Fracture Zone. Journal of Geophysical ResearchSolid Earth, 103, 21315-33.

    Blackman DK, Karson JA, Kelley DS, Cann JR, Fru€h-Green GL, Gee JS, Hurst SD, John BE, Morgan J, Nooner SL, Ross DK, Schroeder TJ, Williams EA (2002) Geology of the Atlantis Massif (Mid-Atlantic Ridge, 30 degrees N): implications for the evolution of an ultramafic oceanic core complex. Marine Geophysical Researches, 23, 443-69.

    Blackman DK, Ildefonse B, John BE, Ohara Y, Miller DJ, MacLeod CJ, Scientists E (2006) Oceanic core complex formation, atlantis massif. In Proceedings of the Integrated Ocean Drilling Program, Volume 304/305: Integrated Ocean Drill. Program Manage. Int. Inc., College Station, TX. http:// publications.iodp.org/proceedings/304_305/30405title.htm.

    Blackman DK, Ildefonse B, John BE, Ohara Y, Miller DJ, Abe N, Abratis M, Andal ES, Andreani M, Awaji S, Beard JS, Brunelli D, Charney AB, Christie DM, Collins J, Delacour AG, Delius H, Drouin M, Einaudi F, Escartin J, Frost BR, Fru€h-Green G, Fryer PB, Gee JS, Godard M, Grimes CB, Halfpenny A, Hansen HE, Harris AC, Tamura A, Hayman NW, Hellebrand E, Hirose T, Hirth JG, Ishimaru S, Johnson KTM, Karner GD, Linek M, MacLeod CJ, Maeda J, Mason OU, McCaig AM, Michibayashi K, Morris A, Nakagawa T, Nozaka T, Rosner M, Searle RC, Suhr G, Tominaga M, von der Handt A, Yamasaki T, Zhao X (2011) Drilling constraints on lithospheric accretion and evolution at Atlantis Massif, Mid-Atlantic Ridge 30 degrees N. Journal of Geophysical Research-Solid Earth, 116, B07103. doi:10.1029/2010JB007931.

    Blackman DK, Slagle A, Harding A, Guerin G, McCaig AM (2013) Atlantis Massif Oceanic Core Complex: velocity, porosity, and impedance contrasts within the domal core of Atlantis Massif: faults and hydration of lithosphere during core complex evolution. IODP Preliminary Report, 340T.

  • Similar Research Results (1)
  • Metrics
    No metrics available
Share - Bookmark