Plate boundary geometry to Moho depths within the 9 deg 03 min N and 12 deg 54 min N overlapping spreading centers of the East Pacific Rise

Details Plate boundary geometry to Moho depths within the 9 deg 03 min N and 12 deg 54 min N overlapping spreading centers of the East Pacific Rise Plate boundary geometry to Moho depths within the 9 deg 03 min N and 12 deg 54 min N overlapping spreading centers of the East Pacific Rise

Dec 1994

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1994e%26psl.128...99b&link_type=abstract

Earth and Planetary Science Letters (ISSN 0012-821X), vol. 128, no. 3-4, p. 99-112

Mathematics

Logic

5

Bathymeters, Magma, Plate Theory, Sea Floor Spreading, Seismic Energy, Seismology, Three Dimensional Bodies, Amplitudes, Earth Crust, Earth Mantle, Reflectance, Spatial Distribution, Topography, Volcanoes

Scientific paper

Multichannel seismic reflection data from the East Pacific Rise (EPR) provide a three-dimensional view of overlapping spreading centers (OSCs) at 9 deg 03 min N and 12 deg 54 min N. Previous studies of the 9 deg 03 min N OSC, based on position of the axial magma chamber top, are extended to the base of the crust using the observation that the Moho reflection is disrupted in the vicinity of the ridge axis. The smaller 12 deg 54 min N OSC is investigated for comparison. Like the shallower features, the Moho disruption is offset within the OSCs. At the larger 9 deg 03 min N OSC, misalignment between the morphologic ridge axis and the axial magma body extends to the base of the crust, where the axial gap in the reflection Moho does not consistently underlay the shallower structures. Spatial relationships within the OSCs between axial topography, axial magma chamber and axial gap in reflection Moho, suggest that ridge tips propagate first by brittle fracturing of the upper crust, followed by intracrustal magma residence, followed finally by establishment or capture of magma pathways from the mantle. Interpreting all three features as demarcating the axial zone of weakness, along which new magma enters the crust, the axial plane within the 9 deg 03 min N OSC appears to dip and to rotate with depth. The sense of overlap in the shallow crust is dextral while the sense of offset in the deep crust is sinistral. Spatial relationships within the 9 deg 03 min N OSC suggest that the northern, propagating ridge tip has already captured a portion of the deep crustal magma conduit connected with the southern ridge.

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