A magnetic survey of Explorer Seamount— Recent spreading at the Explorer trench |
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| Authors: | Wu Mingxian Patrick J C Ryall Joanne Bryan |
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| Institution: | (1) Shandong College of Oceanology, Shandong, China;(2) Department of Geology, Dalhousie University, Halifax, Nova Scotia |
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| Abstract: | In 1981 a magnetic and bathymetric survey was carried out over Explorer Seamount located approximately between 48°50′ and
49°30′N and 130°40′ and 131°30′W. During the cruise four pillow fragments were dredged from peaks in this area. Based on the
observed magnetic data, it was identified that the main peak of Explorer Seamount should be of the Bruhnes age while the magnetic
high in the NW of study area would be Gauss. This would yield a spreading rate of about 2 cm per year for the Matuyama epoch.
The results of intensities of remanence measured from the pillow fragments indicate that the ages are less than 106 years. Similarly the Curie temperature is consistent with ages of around 106 years. An attempt was made to model the observed magnetic field using a series of uniformly magnetized NE-SW trending blocks
of alternating polarity. Agreement between the model and observed results is satisfied. Oxidation ratios calculated from measured
samples suggest that the main peak of Explorer Seamount is not far from the present day ridge axis, which agrees with the
younger interpretation from the magnetic profiles.
The results mentioned above strongly, but not conclusively, favour an interpretation in which the southeastern peak of Explorer
Seamount is of the Bruhnes age and the recent spreading is at Explorer trench, then the Sovanco Fracture Zone should be thought
of as a complex triangular area between the northern end of Juan de Fuca Ridge and Explorer Seamount rather than as a simple
transform fault as defined conventionally. |
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