Structure of the southern Juan de Fuca Ridge from seismic reflection records

Twenty-four-channel seismic reflection records were obtained from the axial region of the southern Juan de Fuca Ridge. Two profiles are normal to the strike of the spreading center and intersect the ridge at latitude 44°40′N and 45°05′N; a third profile extends south along the ridge axis from latitude 45°20′N and crosses the Blanco Fracture Zone. Processing of the axial portions of the cross-strike lines resolved a weak reflection centered beneath the axis. The reflector is at a depth similar to seismically detected magma chambers on the East Pacific Rise and a Lau Basin spreading center; we suggest that the reflector represents the top of an axial magma chamber. In the migrated sections the top of the probable magma chamber is relatively flat and 1–2 km wide, and the subbottom depth of the chamber is greater where the depth to the ridge axis is greater.

[1]  W. Normark,et al.  Submersible observations along the southern Juan de Fuca Ridge: 1984 Alvin Program , 1987 .

[2]  K. V. Damm,et al.  Chemistry of hydrothermal solutions from the southern Juan de Fuca Ridge , 1987 .

[3]  J. Mutter,et al.  Multi-channel seismic imaging of a crustal magma chamber along the East Pacific Rise , 1987, Nature.

[4]  D. Clague,et al.  Gabbroic xenoliths and host ferrobasalt from the southern Juan de Fuca Ridge , 1986 .

[5]  J. McClain,et al.  The East Pacific Rise in cross section: A seismic model , 1985 .

[6]  D. Clague,et al.  Mineralogy and chemistry of massive sulfide deposits from the Juan de Fuca Ridge , 1984 .

[7]  P. Newman.  Seismic Response to Sea-Floor Diffractors , 1984 .

[8]  J. Eissen,et al.  Time and space constraints on the evolution of medium-rate spreading centers , 1983 .

[9]  Robert D. Ballard,et al.  The East Pacific Rise near 21°N, 13°N and 20°S: inferences for along-strike variability of axial processes of the Mid-Ocean Ridge , 1983 .

[10]  C. Lister,et al.  On the intermittency and crystallization mechanisms of sub-seafloor magma chambers , 1983 .

[11]  D. Clague,et al.  Active hydrothermal vents and sulfide deposits on the southern Juan de Fuca Ridge , 1983 .

[12]  N. Sleep,et al.  Reinterpretation of seismic reflection data over the East Pacific Rise , 1982 .

[13]  J. Delaney,et al.  The Juan de Fuca Ridge—Hot Spot—Propagating Rift System: New tectonic, geochemical, and magnetic data , 1981 .

[14]  P. Stoffa,et al.  Structure of the East Pacific Rise crest from multichannel seismic reflection data , 1978 .

[15]  E. Davis,et al.  Seismic structure of the Juan de Fuca Ridge: Ocean bottom seismometer results from the Median Valley , 1976 .

[16]  C. H. Dix.  REFRACTION AND REFLECTION OF SEISMIC WAVES—II DISCUSSION OF THE PHYSICS OF REFRACTION PROSPECTING , 1939 .

[17]  W. Normark.  Submarine fissure eruptions and hydrothermal vents on the southern Juan de Fuca Ridge: preliminary observations from the submersible Alvin , 1986 .

[18]  J. B. Rapp,et al.  Basalt samples and water-column samples from the southern Juan de Fuca Ridge; preliminary results of cruise L13-82-WF , 1983 .

[19]  J. Delaney,et al.  Photogeology and evolution of the Juan de Fuca Ridge , 1983 .

[20]  D. Clague,et al.  Preliminary description of basalt from the southern Juan de Fuca Ridge , 1982 .

[21]  J. Delaney,et al.  Geologic setting of massive sulfide deposits and hydrothermal vents along the southern Juan de Fuca Ridge , 1982 .

[22]  Jon F. Claerbout,et al.  Velocity estimation in laterally varying media , 1979 .

[23]  A. Cooper,et al.  Collection, reduction, and interpretation of marine seismic sonobuoy data , 1978 .