COMPARISON OF OCEANIC CRUST ACCRETION FEATURES WITH LOW-VELOCITY AND ULTRALOW-VELOCITY SPREADING
Рубрики: ОРИГИНАЛЬНЫЕ СТАТЬИ
Авторы:
1.
VNII "Okeanologia" Sankt-Petersburg, Russia
2.
VNII "Okeanologia" Sankt-Petersburg, Russia
3.
VNII "Okeanologia" Sankt-Petersburg, Russia
4.
VNII "Okeanologia" Sankt-Petersburg, Russia
Тип:
Статья
Страницы:
с 295
по 301
Статус:
Опубликован
Получено:
25.02.2001
Одобрено:
25.02.2001
Опубликовано:
25.02.2001
Язык материала:
английский
Ключевые слова:
oceanic crust, accretion, spreading, Mid-Atlantic Ridge, Gakkel Ridge.
Аннотация (русский):
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 24o N and 29o N and in the southeastern segment of the Gakkel ultralow-velocity spreading ridge in the Polar Ocean, between 81o 16 N and 84o 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.
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 24o N and 29o N and in the southeastern segment of the Gakkel ultralow-velocity spreading ridge in the Polar Ocean, between 81o 16 N and 84o 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.
Ключевые слова:
oceanic crust, accretion, spreading, Mid-Atlantic Ridge, Gakkel Ridge.
oceanic crust, accretion, spreading, Mid-Atlantic Ridge, Gakkel Ridge.
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3. Mevel, Inter Ridge News, v. 7, no. 1, 1998.
4. Purdy, Marine Geophys. Res., v. 12, 1990.
5. Sempere, Nature, v. 344, 1990.
