Structure of the hydrothermal root zone of the sheeted dikes in fast-spread oceanic crust : a core-log integration study of ODP hole 1256D, Eastern Equatorial Pacific - Archive ouverte HAL Access content directly
Journal Articles Ofioliti Year : 2012

Structure of the hydrothermal root zone of the sheeted dikes in fast-spread oceanic crust : a core-log integration study of ODP hole 1256D, Eastern Equatorial Pacific

Marie Violay
Philippe Pezard
  • Function : Author
  • PersonId : 861998
Benoit Ildefonse
Bernard Celerier
  • Function : Author
  • PersonId : 862906
Agathe Deleau
  • Function : Author

Abstract

Ocean Drilling Program Hole 1256D reached for the first time the transition zone between the sheeted dike complex and the uppermost gabbros. The recovered crustal section offers a unique opportunity to study the deepest part of the hydrothermal system in present-day oceanic crust. We present a structural analysis of electrical borehole wall images. We identified, and measured the orientations of four categories of structures: major faults, minor fractures, possibly hydrothermal veins, and dikes. All structures tend to strike parallel to the paleo-ridge axis. Three major fault zones (meter thick) and dikes are steeply dipping (~ 75° on average) outward the ridge. Centimeter-thick moderately conductive planar features are interpreted as hydrothermal veins, are organized in arrays of consistent spacing, thickness, and orientation, and are dipping about 15-20° toward the ridge. This structural pattern is interpreted as an on-axis paleohydrothermal circulation system, with vertical, dike-parallel fractures, and sub-horizontal high-temperature hydrothermal veins at the base of the sheeted dike, which was subsequently rotated ~ 15° westward around a ridge-parallel, sub-horizontal axis. This rotation can be caused by upper-crustal block rotation along a listric normal fault, and/or subsidence at the ridge axis.
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hal-00757592 , version 1 (27-11-2012)

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Marie Violay, Philippe Pezard, Benoit Ildefonse, Bernard Celerier, Agathe Deleau. Structure of the hydrothermal root zone of the sheeted dikes in fast-spread oceanic crust : a core-log integration study of ODP hole 1256D, Eastern Equatorial Pacific. Ofioliti, 2012, 37 (1), pp.1-11. ⟨10.4454/ofioliti.v37i1.402⟩. ⟨hal-00757592⟩
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