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

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Date
2011-07-19
Authors
Blackman, Donna K.
Ildefonse, Benoit
John, Barbara E.
Ohara, Y.
Miller, D. J.
Abe, Natsue
Abratis, M.
Andal, E. S.
Andreani, Muriel
Awaji, S.
Beard, J. S.
Brunelli, Daniele
Charney, A. B.
Christie, D. M.
Collins, John A.
Delacour, A. G.
Delius, H.
Drouin, M.
Einaudi, F.
Escartin, Javier E.
Frost, B. R.
Fruh-Green, Gretchen L.
Fryer, P. B.
Gee, Jeffrey S.
Grimes, C. B.
Halfpenny, A.
Hansen, H.-E.
Harris, Amber C.
Tamura, A.
Hayman, Nicholas W.
Hellebrand, Eric
Hirose, T.
Hirth, Greg
Ishimaru, S.
Johnson, Kevin T. M.
Karner, G. D.
Linek, M.
MacLeod, Christopher J.
Maeda, J.
Mason, O..U.
McCaig, A. M.
Michibayashi, K.
Morris, Antony
Nakagawa, T.
Nozaka, Toshio
Rosner, Martin
Searle, Roger C.
Suhr, G.
Tominaga, Masako
von der Handt, A.
Yamasaki, T.
Zhao, Xixi
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DOI
10.1029/2010JB007931
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Keywords
Atlantis Massif
Integrated Ocean Drilling Program
Oceanic Core Complex
Abstract
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° 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 ∼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.
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Author Posting. © American Geophysical Union, 2011. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Journal of Geophysical Research 116 (2011): B07103, doi:10.1029/2010JB007931.
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Journal of Geophysical Research 116 (2011): B07103
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