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Oceanography, 2012
 | | » | 40. R2K Seismic Studies
Oceanography, 2012
| | » | 39. Melt bodies off the EPR
Nature Geoscience, 2012
| | » | 38. JdF Plate: Gravity structure
G-cubed, 2011
| | » | 37. JdF Plate: Layer 2B structure
G-cubed, 2011
| | » | 36. Kane waveform tomography
GRL, 2010
| | » | 35. Kane Oceanic Core Complex
G-cubed, 2009
| | » | 34. Geophysical signatures of oceanic core complexes
GJI, 2009
| | » | 33. Accretion of the lower crust
Nature, 2009
| | » | 32. Faulting of the Juan de Fuca plate
EPSL, 2009
| | » | 31. Axial topography os the Galapagos Spreading Center
G-cubed, 2008
| | » | 30. Juan de Fuca Ridge flanks
G-cubed, 2008
| | » | 29. Seismic structure of oceanic core complexes
G-cubed, 2008
| | » | 28. Juan de Fuca Ridge: structure and hotspots
G-cubed, 2008
| | » | 27. Structure of the TAG segment, Mid-Atlantic Ridge
G-cubed, 2007
| | » | 26. Detachment faulting at TAG, Mid-Atlantic Ridge
Geology, 2007
| | » | 25. Structure of the Endeavour segment, Juan de Fuca Ridge
JGR, 2007
| | » | 24. Magma beneath Lucky Strike Hydrothermal Field
Nature, 2006
| | » | 23. Magma chamber of the Cleft segment, Juan de Fuca Ridge
EPSL, 2006
| | » | 22. Topography and magmatism at the Juan de Fuca Ridge
Geology, 2006
| | » | 21. Structure of the southern Juan de Fuca Ridge
JGR, 2005
| | » | 20. Sub-crustal magma lenses
Nature, 2005
| | » | 19. Constructing the crust at the Galapagos Spreading Center
JGR, 2004
| | » | 18. Atlantis core complex
EPSL, 2004
| | » | 17. Morphology of the Galapagos Spreading Center
G-cubed, 2003
| | » | 16. Crustal structure of the East Pacific Rise
GJI, 2003
| | » | 15. Plume-ridge interaction along the Galapagos Spreading Center
G-cubed, 2002
| | » | 14. Compensation of the Galapagos swellEPSL, 2002
| | » | 13. Structure of Tenerife, Canary Islands
JVGR, 2000
| | » | 12. Underplating in the Canary Islands
JVGR, 2000
| | » | 11. Structure of the Mid-Atlantic Ridge (MARK, 23?20'N)
JGR, 2000
| | » | 10. Structure of the Mid-Atlantic Ridge (35?N)
JGR, 2000
| | » | 9. Structure of Gran Canaria, Canary Islands
J. Geodyn., 1999
| | » | 8. Structure of overlapping spreading centers in the MELT area
GRL, 1998
| | » | 7. Crustal thickness in the MELT area
Science, 1998
| | » | 6. The MELT experiment
Science, 1998
| | » | 5. The Canary Islands swell
GJI, 1998
| | » | 4. Morphology of the Galapagos Spreading Center
JGR, 1997
| | » | 3. Faulting of slow-spreading oceanic crust
Geology, 1997
| | » | 2. Flexure beneath Tenerife, Canary Islands
EPSL, 1997
| | » | 1. Elastic thickness in the Canary Islands
GRL, 1994
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Canales, J.P., B.E. Tucholke, and J.A. Collins, Seismic imaging of an oceanic detachment fault: Atlantis Megamullion (Mid-Atlantic Ridge, 30?10'N), Earth Planet. Sci. Lett., 222, 543-560, 2004
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Abstract
We present multichannel seismic reflection data collected over the Atlantis megamullion, at the eastern ridge-transform intersection of Atlantis fracture zone on the northern Mid-Atlantic Ridge, and over its conjugate crust. These data image for the first time the internal structure of a young, well developed megamullion dome formed by tectonic extension across a long-lived oceanic detachment fault. The exposed, corrugated detachment-fault surface exhibits a sharp, coherent reflection that contrasts with less organized reflectivity of surrounding basaltic seafloor. At the termination of the megamullion the fault is imaged ~13 km along-strike beneath a volcanic hanging-wall block at a sub-seafloor depth of 0.2-0.5 s two-way travel time, reaching north as far as 30?19?N. The eastward dipping of the fault beneath the hanging-wall block is estimated to be ~6?-14?. The corrugated fault surface is underlain by a continuous, strong, and relatively smooth reflection (D) at 0.2-0.25 s sub-bottom below the central axis of the dome. This reflection deepens up to 0.6 s sub-bottom beneath the western slope and it appears to intersect the seafloor on the eastern slope. We suggest that Atlantis massif formed by sequential slip on two different detachment faults that merged at depth, with breakaways as little as ~2 km apart. The initial detachment is represented by reflection D, and the second corresponds to the presently exposed fault surface. In this interpretation, much of the sliver between the faults is interpreted to be strongly serpentinized peridotite with reduced seismic velocity; it lies in contact with less altered, higher-velocity mantle below the first detachment, resulting in the strong, smooth character of reflection D. Mantle rocks exposed in the megamullion indicate that the feature formed during a period of extreme tectonic extension and probably limited magmatism. In conjugate crust corresponding to termination of the megamullion, observed sub-bottom reflections are interpreted as base of seismic layer 2A. This layer is as thick as or thicker (~570-900 m) than layer 2A in normal Atlantic crust, and it suggests that relatively normal crustal accretion occurred by the time the megamullion stopped forming. |
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