Data/hora: 08/06/2024 11:31:45

Provedor de dados: 	5	
País: 	France	
Título: 	Geological context and vents morphology of the ultramafic-hosted Ashadze hydrothermal areas (Mid-Atlantic Ridge 13 degrees N)	
Autores: 	Ondreas, Helene; Cannat, Mathilde; Fouquet, Yves; Normand, Alain.	
Data: 	2012-11	
Ano: 	2012	
Palavras-chave: 	Ashadze; Mid-Atlantic Ridge; Hydrothermal activity; Hydrothermal explosion crater; Ultramafic rocks.	
Resumo: 	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.	
Tipo: 	Text	
Idioma: 	Inglês	
Identificador: 	http://archimer.ifremer.fr/doc/00111/22223/19895.pdf

DOI:10.1029/2012GC004433	
Editor: 	Amer Geophysical Union	
Relação: 	http://archimer.ifremer.fr/doc/00111/22223/	
Formato: 	application/pdf	
Fonte: 	Geochemistry Geophysics Geosystems (1525-2027) (Amer Geophysical Union), 2012-11 , Vol. 13 , N. 1 , P. Q0AG14	
Fonte: 	2012. American Geophysical Union. All Rights Reserved.