Overlapping spreading centres: new accretion geometry on the East Pacific Rise

  title={Overlapping spreading centres: new accretion geometry on the East Pacific Rise},
  author={Ken C. Macdonald and Paul J. Fox},
In a detailed Seabeam investigation of the East Pacific Rise (EPR) from 8°N to 18°N, a new kind of volcano-tectonic geometry associated with fast-spreading centres has been discovered (Figs 1, 2). At several locations along the rise axis the neovolcanic zone is discontinuous, and is laterally offset a short distance (1–15 km). In contrast to a classic ridge–transform–ridge plate boundary, however, the offset ridge terminations overlap each other by a distance approximately equal to or greater… 
Fine scale study of a small overlapping spreading center system at 12°54′ N on the East Pacific Rise
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A Seabeam and magnetometer survey of the Pacific-Nazca plate boundary around 5.5°S mapped a “nontransform offset” whose geology and kinematics seem typical of a whole class of structures formed where
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Summary. Overlapping spreading centres (OSCs) represent a new type of plate boundary interaction in which en echelon rise segments overlap significantly and are not joined by a transform fault.
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Asymmetric sea-floor spreading and a nontransform axis offset: The East Pacific Rise 20°S survey area
Data obtained from the East Pacific Rise near 20°S provide an opportunity to make a detailed study of an asymmetrically spreading rise crest. During the past 2.4 m.y., crustal accretion has occurred
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A deeply-towed instrument package was used in a detailed survey of the crest of the East Pacific Rise (EPR) near 3°25′S, where the Pacific and Nazca plates are separating at 152 mm/yr. A single 90
Northern East Pacific Rise' Magnetic Anomaly and Bathymetric Framework
The oceanic crust in the eastern Pacific between 7oN and 30oN and east of 127oW contains a fairly complete history of the spreading centers associated with the East Pacific Rise since 25 m.y.B.P.
Propagating rifts on midocean ridges
Spreading center jumps identified west of the Galapagos Islands near 95°W occur in a pattern consistent with the propagating rift hypothesis. A new rift is gradually breaking through the Cocos plate.
Mid-Ocean Ridges: Fine Scale Tectonic, Volcanic and Hydrothermal Processes Within the Plate Boundary Zone
A first order model of spreading centers as idealized linear boundaries of crustal and lithospheric generation provides only a gross understanding of global scale plate kinematics. As we attempt to
Evolution of oceanic crust: 2. Constraints, implications, and inferences
In part 1 (Rosendahl et al., 1976) of this study it was found that a wedge-shaped low-velocity zone underlies the axial block of the East Pacific Rise. This low-velocity zone, which occurs within the
Structure of the East Pacific Rise from an Ocean Bottom Seismometer Survey
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East Pacific Rise: Hot Springs and Geophysical Experiments
High-resolution determinations of crustal properties along the spreading center were made to gain knowledge of the source of new oceanic crust and marine magnetic anomalies, the nature of the axial magma chamber, and the depth of hydrothermal circulation.
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Fifty acoustically positioned samples of fresh basalt were collected by the submersible Alvin from the median valley of the Mid-Atlantic Ridge during the French American Mid-Ocean Undersea Study