Comparison of oceanic crust accretion features with...

RUSSIAN JOURNAL OF EARTH SCIENCES VOL. 2, NO. 3, PAGES 295–301, doi:10.2205/2000ES000046, 2000

Comparison of oceanic crust accretion features with low-velocity and ultralow-velocity spreading

E. G. Astafurova, N. I. Gurevich, E. D. Daniel', and S. P. Mashchenkov

VNII Oceanology, Sankt-Peterburg, Russia

Abstract

[1] The aim of this study was to compare the main characteristics of the axial zones of the low-velocity Mid-Atlantic Ridge (MAR) in the strip of the Canary-Bahama Islands between 24^o N and 29^o N and in the southeastern segment of the Gakkel ultralow-velocity spreading ridge in the Polar Ocean, between 81^o 16 N and 84^o 30 N. The results of this comparison showed that the colder thermal conditions of the lithosphere during the super-low velocity spreading, associated with the lower amount of the melt rising from the mantle, led to the predominance of tectonic extension and to the more scarce formation of volcanic centers in the vicinity of the Gakkel Ridge axis, compared to MAR; to the broader and deeper rift valley of the Gakkel Ridge, which can be filled by local volcanic cones because of the varying magma supply; to the differences in the style of the geomorphologic segmentation, expressed in the absence of the displacements of the rift valley and its floor in the vicinity of the boundaries between the Gakkel Ridge segments, and in the topographic differences along the axial profiles of the Gakkel and Mid-Atlantic ridges; to the thinning of the earth crust and to its other features along its variations in the Gakkel Ridge, compared to the MAR crust. These differences are reflected in the types of their geophysical fields. Owing to the insignificant crustal thickness variations, most of the Gakkel Ridge segments are not marked by any mantle Bouguer anomalies. At the same time, the segments including volcanic centers, are marked by highly variable mantle Bouguer anomalies and, hence, by highly variable crustal thickness, compared to those of the Middle Atlantic Ridge. This proves that the Gakkel Ridge shows a more complicated association between its anomalous magnetic field and volcano-tectonic conditions, compared to the Middle Atlantic Ridge.

Received 16 November 2000; published 15 January 2001.

Keywords: oceanic crust, accretion, spreading, Mid-Atlantic Ridge, Gakkel Ridge.

Citation: Astafurova, E. G., N. I. Gurevich, E. D. Daniel', and S. P. Mashchenkov (2000), Comparison of oceanic crust accretion features with low-velocity and ultralow-velocity spreading, Russ. J. Earth Sci., 2, No.3, 295-301, doi:10.2205/2000ES000046.