HAL : hal-00617528, version 1

DOI : 10.1029/2010JB007931

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Journal of Geophysical Research 116 (2011) B07103

Drilling constraints on lithospheric accretion and evolution at Atlantis Massif, Mid-Atlantic Ridge 30 degrees N

D. K. Blackman 1, Benoit ILDEFONSE 2, B. E. John 3, Y. Ohara 4, D. J. Miller 5, N. Abe 6, M. Abratis 7, E. S. Andal 8, Muriel Andreani 2, 9, S. Awaji 10, J. S. Beard 11, D. Brunelli 12, A. B. Charney 13, D. M. Christie 14, J. Collins 15, A. G. Delacour 16, H. Delius 17, Marion Drouin 2, F. Einaudi 2, J. Escartin 18, B. R. Frost 3, G. Frueh-Green 19, P. B. Fryer 20, J. S. Gee 1, Marguerite GODARD 2, C. B. Grimes 21, A. Halfpenny 22, H. -E. Hansen 23, A. C. Harris 24

(2011)

Expeditions 304 and 305 of the Integrated Ocean Drilling Program cored and logged a 1.4 km section of the domal core of Atlantis Massif. Postdrilling research results summarized here constrain the structure and lithology of the Central Dome of this oceanic core complex. The dominantly gabbroic sequence recovered contrasts with predrilling predictions; application of the ground truth in subsequent geophysical processing has produced self-consistent models for the Central Dome. The presence of many thin interfingered petrologic units indicates that the intrusions forming the domal core were emplaced over a minimum of 100-220 kyr, and not as a single magma pulse. Isotopic and mineralogical alteration is intense in the upper 100 m but decreases in intensity with depth. Below 800 m, alteration is restricted to narrow zones surrounding faults, veins, igneous contacts, and to an interval of locally intense serpentinization in olivine-rich troctolite. Hydration of the lithosphere occurred over the complete range of temperature conditions from granulite to zeolite facies, but was predominantly in the amphibolite and greenschist range. Deformation of the sequence was remarkably localized, despite paleomagnetic indications that the dome has undergone at least 45 degrees rotation, presumably during unroofing via detachment faulting. Both the deformation pattern and the lithology contrast with what is known from seafloor studies on the adjacent Southern Ridge of the massif. There, the detachment capping the domal core deformed a 100 m thick zone and serpentinized peridotite comprises similar to 70% of recovered samples. We develop a working model of the evolution of Atlantis Massif over the past 2 Myr, outlining several stages that could explain the observed similarities and differences between the Central Dome and the Southern Ridge.

1 :	University of California, San Diego, La Jolla
	inconnue
2 :	Géosciences Montpellier (GM)
	CNRS : UMR5243 – Université Montpellier II - Sciences et techniques
3 :	University of Wyoming, Laramie
	inconnue
4 :	Ocean Research Laboratory, Tokyo
	inconnue
5 :	Texas A&M University, College Station
	inconnue
6 :	JAMSTEC, Yokosuka
	inconnue
7 :	Friedrich Schiller University of Jena
	inconnue
8 :	8Philex Mining Corporation, Pasig City
	inconnue
9 :	Laboratoire de Géologie de Lyon - Terre, Planètes, Environnement (LGL-TPE)
	CNRS : UMR5276 – INSU – Université Claude Bernard - Lyon I – École Normale Supérieure - Lyon
10 :	University of Tokyo,
	inconnue
11 :	11Virginia Museum of Natural History, Martinsville
	inconnue
12 :	Universita Modena, Modena
	inconnue
13 :	Oregon State University, Corvalis
	inconnue
14 :	University of Alaska Fairbanks
	inconnue
15 :	Woods Hole Oceanographic Institution, Woods Hole
	inconnue
16 :	Laboratoire de Dynamique Terrestre et Planétaire
	Observatoire Midi-Pyrénées – Université Paul Sabatier [UPS] - Toulouse III
17 :	University of Leicester
	inconnue
18 :	Institut de Physique du Globe de Paris (IPGP)
	CNRS : UMR7154 – INSU – IPG PARIS – Université Pierre et Marie Curie [UPMC] - Paris VI – Université Paris VII - Paris Diderot – Université de la Réunion
19 :	Eldgenössische Technische Hochschule Zürich (ETH Zürich)
	ETH Zurich
20 :	University of Hawaii at Manoa, Honolulu,
	inconnue
21 :	Mississippi State University
	inconnue
22 :	Australian National University, Canberra
	inconnue
23 :	University of Bergen, Bergen,
	inconnue
24 :	Norwich University, Northfield, Vermont
	inconnue

Équipe de recherche : Manteau et Interfaces

Domaine

:

Planète et Univers/Sciences de la Terre/Océanographie

Mots Clés : Atlantis Massif – Integrated Ocean Drilling Program – Oceanic Core Complex

hal-00617528, version 1

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Contributeur : Gm Aigle <>

Déposé pour le compte de : Benoit ILDEFONSE <>

Soumis le : Vendredi 20 Janvier 2012, 10:54:23

Dernière modification le : Mercredi 15 Février 2012, 15:22:18