Juan de Fuca Ridge atlas: preliminary Seabeam bathymetry

Malahoff, Alexander; Currie, R G; Davis, Earl E.; Riddihough, R P; Sawyer, B

doi:10.4095/130002

Cited by 3 publications

(2 citation statements)

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“…Figure 3. Therefore the latitude of each division is given in Tables 1 and 2, for reference to the 1:50,000 charts [Malahoff et al, 1984].…”

Section: Subsegmentation Of the Sermentioning

confidence: 99%

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Petrologic and geologic variations along the Southern Explorer Ridge, northeast Pacific Ocean

Michael¹,

Chase²,

Allan³

1989

J. Geophys. Res.

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Mid‐ocean ridge basalts (MORB) from the well‐defined Southern Explorer Ridge segment (SER) in the northeast Pacific Ocean are moderately to strongly enriched in incompatible elements. Enriched MORB were erupted at the highest and widest part of the segment (culmination) where the magma supply may be the greatest and also at the northern and southern ends of the SER. Variations in basalts' incompatible element enrichment occur over short distances and suggest that the underlying mantle is heterogeneous on a small scale. The variations also preclude the existence of a long‐lived, well‐mixed magma chamber beneath the robust culmination. Instead, magma chambers are probably temporally and spatially isolated, as evidenced by the presence of highly differentiated lavas. Less enriched (transitional) MORB were erupted along the central part of the SER, 11–27 km south of the culmination, and were supplied to the ridge separately from a less enriched pan of the mantle. A more continuous magma chamber cannot be ruled out for this section on geochemical grounds. All of the MORB from the SER have undergone significant amounts of fractional crystallization. Unlike certain segments of the East Pacific Rise, the most evolved MORB were erupted near the culmination of the ridge segment. Aphyric lavas have been recovered only from the vicinity of the culmination, while phyric lavas have erupted along the entire length of the SER. There is no correlation between composition and total crystal abundances. Despite the requirement of multiple parental magmas, most of the lavas from the culmination and the distal ends of the ridge fall on a common liquid line of descent, indicating that they formed at similar depths and extents of partial melting. The transitional MORB from the central part of the ridge have probably formed by lesser extents of partial melting and separated from their mantle source at greater depths based on abundances of Na and moderately incompatible elements such as Sm and Zr. Enriched, high‐melt fraction lavas at the magma‐starved southern end of the SER closely resemble lavas from the culmination. Either the southernmost lavas have flowed laterally within the crust from near the culmination, or there is another melting anomaly that supplies the southern end of the SER. If the latter case is true, correspondence between ridge morphology and mantle thermal state is poor.

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“…Figure 3. Therefore the latitude of each division is given in Tables 1 and 2, for reference to the 1:50,000 charts [Malahoff et al, 1984].…”

Section: Subsegmentation Of the Sermentioning

confidence: 99%

“…The ED is a 4 to 8-km-wide basin, up to 3100 m deep [Grill et al, 1981]. Morphology is well depicted on a series of Sea Beam charts [Malahoff et al, 1984;Davis et al, 1985Davis et al, , 1987.…”

mentioning

confidence: 98%

Petrologic and geologic variations along the Southern Explorer Ridge, northeast Pacific Ocean

Michael¹,

Chase²,

Allan³

1989

J. Geophys. Res.

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The influence of primary magma composition, H2O and pressure on mid-ocean ridge basalt differentiation

Michael

Chase

1987

Contr. Mineral. and Petrol.

131

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Geological and geophysical characteristics of the Tuzo Wilson Seamounts: implications for plate geometry in the vicinity of the Pacific – North America – Explorer triple junction

Carbotte¹,

Dixon²,

Farrar³

et al. 1989

Can. J. Earth Sci.

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SeaMARC II imagery, SEABEAM bathymetry, seismic reflection profiles, and gravity and magnetic data are used to establish the tectonic significance of the Tuzo Wilson Seamounts, two submarine volcanic edifices located southwest of the southern end of the Queen Charlotte transform fault. SeaMARC II imagery reveals a parallel transform fault, an extension of the Revere–Dellwood Fault, bordering the southwest end of the Dell wood Knolls and terminating at the southwest end of the Tuzo Wilson Seamounts. This transform-fault system links spreading at the north end of Explorer Ridge to extension at the Tuzo Wilson Seamounts. An inactive continuation of this transform 50 km to the northwest of Tuzo Wilson Seamounts is inferred from seismic profiles. Between Dellwood Knolls and Tuzo Wilson Seamounts, this transform fault has offset Pleistocene (ca. 10 000 a) sea-bed features in a right-lateral sense by 250 m and has offset part of the Dellwood Knolls volcanic edifice by 6–8 km. Numerous normal faults at the Tuzo Wilson Seamounts and Dellwood Knolls are roughly orthogonal to the Queen Charlotte and Revere–Dellwood transforms and indicate rifting in an extensional jog between the transforms. Seismic profiles reveal sediments and basement back-tilted northwest and southeast away from the Tuzo Wilson Seamounts, also consistent with extension. Acoustic imagery indicates that the Tuzo Wilson Seamounts are surrounded by basalt flows that are largely free of sediment cover and thus postdate recent rapid sedimentation (< 10 000 a). In contrast, few of the flows around Dellwood Knolls are free of sediment. Basalts from the Tuzo Wilson Seamounts have high magnetizations (average 35 A/m) and are free of manganese encrustation. Tuzo Wilson Seamounts have a + 1000 nT magnetic anomaly, which can be modelled with normal, high-intensity (up to 40 A/m) magnetization and with geometry and depth matching the topography of the seamounts and surficial basalt flows. Their small, positive free-air gravity is largely accounted for by their topography; no appreciable local density contrast exists below the surrounding sea floor.The Tuzo Wilson Seamounts and Dellwood Knolls are separate sites of sea-floor spreading, although the partition of spreading between them is indeterminate. The 50 km inactive continuation of the Revere–Dellwood transform requires that a total of at least 100 km of sea floor has been created at the Tuzo Wilson and Dellwood spreading centres, probably within the last 2.5 Ma. The sea floor between the Tuzo Wilson Seamounts and Dellwood Knolls either is a separate microplate or is under going distributed strain. The triple junction of the Pacific, North America, and Explorer plates is not a discrete point; rather it occupies the strained and seismically active region between the northern Explorer Ridge and the Tuzo Wilson Seamounts.

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Juan de Fuca Ridge atlas: preliminary Seabeam bathymetry

Cited by 3 publications

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Petrologic and geologic variations along the Southern Explorer Ridge, northeast Pacific Ocean

Petrologic and geologic variations along the Southern Explorer Ridge, northeast Pacific Ocean

The influence of primary magma composition, H2O and pressure on mid-ocean ridge basalt differentiation

Geological and geophysical characteristics of the Tuzo Wilson Seamounts: implications for plate geometry in the vicinity of the Pacific – North America – Explorer triple junction

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