| Type |
Article |
| Date |
2012-11 |
| Language |
English |
| Author(s) |
Ondreas Helene1, Cannat Mathilde2, Fouquet Yves1, Normand Alain1 |
| Affiliation(s) |
1 : IFREMER, Ctr Brest, FR-29280 Plouzane, France.
2 : Univ Paris Diderot, CNRS, Inst Phys Globe Paris, UMR 7154, FR-75238 Paris 05, France. |
| Source |
Geochemistry Geophysics Geosystems (1525-2027) (Amer Geophysical Union), 2012-11 , Vol. 13 , N. 1 , P. Q0AG14 |
| DOI |
10.1029/2012GC004433 |
| WOS© Times Cited |
22 |
| Keyword(s) |
Ashadze, Mid-Atlantic Ridge, hydrothermal activity, hydrothermal explosion crater, ultramafic rocks |
| Abstract |
Recent ROV dives and high-resolution bathymetric data acquired over the Ashadze fields on the Mid-Atlantic Ridge (13 degrees N) allow us to derive constraints on the regional and local geological setting of ultramafic-hosted hydrothermal fields. The active vent fields of Ashadze hydrothermal fields are located in the western axial valley wall, downslope from the termination of a prominent corrugated surface and in a transitional domain with respect to ridge segmentation. The study of the shipboard and ROV bathymetry shows that decameter (100 m by 60 m) to kilometer-scaled rockslides shape the axial valley wall slopes in this region. The Ashadze 1 vent field occurs on a coherent granular landslide rock mass that is elongated in an E-W direction. The Ashadze 1 vent field comprises hundreds of active and inactive sulfide chimneys. The Ashadze 2 vent field is located in a NNE-trending linear depression which separates outcrops of gabbros and serpentinized peridotites. Active black smokers in the Ashadze 2 field are located on ultramafic substratum in a 40-m diameter crater, 5-m deep. This crater recalls similar structures described at some vents of the Logatchev hydrothermal field (Mid-Atlantic Ridge 15 degrees N). We discuss the mode of formation for these craters, as well as that for a breadcrust-like array of radial fissures identified at Ashadze 1. We propose that hydrothermalism at Ashadze can be an explosive phenomena associated with geyser-like explosions. Our study also constrains the geological and geophysical context of the ultramafic-hosted Ashadze hydrothermal system that may use the oceanic detachment fault as a preferred permeability conduit. |
| Full Text |
| File |
Pages |
Size |
Access |
| Publisher's official version |
20 |
2 MB |
Open access |
|
