Bj. Murton et Lm. Parson, SEGMENTATION, VOLCANISM AND DEFORMATION OF OBLIQUE SPREADING CENTERS - A QUANTITATIVE STUDY OF THE REYKJANES RIDGE, Tectonophysics, 222(2), 1993, pp. 237-257
New multi-beam swath bathymetry charts and high-resolution side-scan s
onar imagery provide detailed evidence for volcanic and magmatic segme
ntation along the Reykjanes Ridge. By combining these data sets, we ha
ve quantified some relationships between different orders of segmentat
ion, various characteristics of volcanism, and changes in tectonism al
ong the ridge axis. Three orders of segmentation along the Reykjanes R
idge have been recognised: (1) A long-wavelength depth variation, or s
well, that is related to the shoaling of the ridge towards Iceland; (2
) Intermediate-wavelength rises of the order of 40-120 km; and (3) A s
hort-wavelength, volcanic segmentation of the order of 5-30 km. The lo
ng-wavelength depth variation, which is probably controlled by the tem
perature of the underlying asthenosphere, has a maximum positive devia
tion from a predicted depth curve that forms a break in slope at 59-60
-degrees-N. This feature migrated southward along the ridge at between
5 and 10 cm/yr at least four times in the past 10 Ma. The intermediat
e-wavelength rises, which are also temporally and spatially unstable,
are probably related to local Rayleigh-Taylor style asthenospheric ins
tabilities. The short-wavelength segments have an evolutionary life-cy
cle, starting with eruption via fissure volcanoes, and progressing by
increasing magma flux to the formation of conical, and then shield-lik
e, volcanoes. These segments are tectonically dismembered by extension
al faulting, following a rapid decrease in magma supply. We propose a
model for the construction of the volcanic layer of the Reykjanes Ridg
e which involves a cyclicity of magmatic and tectonic activity.