HR: 1340h
AN: T23B-1410 INVITED    [Abstracts]
TI: Quantifying the Role of Active Detachment Faulting in Lithospheric Accretion Along Slow–Spreading Ridges (MAR 12-35°N)
AU: Escartín, J J
EM: escartin@ipgp.jussieu.fr
AF: CNRS, IPGP Case 89, 4 Place Jussieu, Paris, 75252, France
AU: * Smith, D K
EM: dsmith@whoi.edu
AF: Woods Hole Oceanographic Institution, MS 22, Woods Hole, MA 02543, United States
AU: Schouten, H
EM: hschouten@whoi.edu
AF: Woods Hole Oceanographic Institution, MS 22, Woods Hole, MA 02543, United States
AU: Cannat, J
EM: j.cann@see.leeds.ac.uk
AF: University of Leeds, School of Earth and Environment, Leeds, LS2 9JT, United Kingdom
AB: We have systematically examined the seafloor morphology along both flanks of the Mid-Atlantic Ridge (MAR) axis between the Marathon and the Oceanographer Fracture zones (FZs), using available multibeam data. We find that detachment faulting may be active along more than 35% of this section of the northern MAR. Our interpretation is based on the findings that showed that the seafloor along the 12- 14°N section of the the MAR [Smith et al. 2006] is characterized by prominent linear ridges with significant outward facing slopes, and associated striated fault surfaces exposed at the seafloor. This terrain, which is interpreted to be the result of detachment faulting and core complex formation, is common throughout the northern MAR, and is systematically associated with zones of enhanced seismicity. The proportion of the axis dominated by detachment faulting varies from ~15% between the Hayes and Oceanographer FZs to >60% between the Marathon and Fifteen-Twenty FZs. Magmatic terrain is characterized by volcanic morphology and fault-bound abyssal hills subparallel to the axis. This terrain, which is associated with limited tectonic extension and aseismic zones, dominates accretion along 30% of the ridge axis. The remaining seafloor flanking the axis (25%) is difficult to classify, and corresponds to either oblique portions of the MAR with complex tectonic and magmatic features, or to areas with limited data coverage. Detachment faulting thus appears to play a larger role in lithospheric accretion along slow spreading ridges than that suggested by the striated fault surfaces alone. The two distinct seafloor morphologies correspond to sections of the ridge with different thermal states, as indicated by the seismic patterns, and probably linked to differences in magmatic supply to the axis.
DE: 3045 Seafloor morphology, geology, and geophysics
DE: 8004 Dynamics and mechanics of faulting (8118)
DE: 8010 Fractures and faults
DE: 8034 Rheology and friction of fault zones (8163)
DE: 8164 Stresses: crust and lithosphere
SC: Tectonophysics [T]
MN: 2007 Fall Meeting