@article{Violay*_Pezard_Ildefonse_Célérier_Deleau_2012, title={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}, volume={37}, url={https://www.ofioliti.it/index.php/ofioliti/article/view/402}, DOI={10.4454/ofioliti.v37i1.402}, abstractNote={<p>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.</p>}, number={1}, journal={Ofioliti}, author={Violay*, Marie and Pezard, Philippe A. and Ildefonse, Benoit and Célérier, Bernard and Deleau, Agathe}, year={2012}, month={Jun.}, pages={1-11} }