LING ZiLong,
GAO JinYao,
ZHAO LiHong et al
.2019.The asymmetric crustal structures of basement ridges of the Gakkel Ridge Chinese Journal of Geophysics(in Chinese),62(5): 1755-1771,doi: 10.6038/cjg2019M0366
1. Shandong University of Science and Technology, Qingdao 266590, China; 2. Key Laboratory of Submarine Geosciences, State Oceanic Administration, Second Institute of Oceanography, Ministry of Natural Resources, Hangzhou 310012, China; 3. Laboratory for Marine Mineral Resources, Pilot National Laboratory for Marine Science and Technology, Qingdao 266237, China; 4. Nanjing University, School of Geography and Ocean Science, Nanjing 210023, China
Abstract：The ultraslow-spreading Gakkel Ridge has six linear basement ridges (A-F) along the spreading direction. They show different degrees of asymmetric geophysical signatures and crustal structures. The spreading rates, residual mantle bouguer anomaly, crustal thickness, and non-isostatic topography of Gakkel Ridge were calculated based on topographic data, free-air gravity anomaly data, and aeromagnetic data. Based on the comparison of topography and crustal thickness on conjugated flanks, we divide basement ridges into symmetric and asymmetric types. In general, the asymmetric amplitude (the absolute value of the difference between conjugated flanks) of topography and crustal thickness of basement ridges in B zone, D zone, and F zone are relatively small, and the asymmetric amplitude of topography is~157 m,~125 m,~208 m, the asymmetric amplitude of crustal thickness is~1 km,~0.06 km,~0.3 km. However, the asymmetric amplitude of topography and crustal thickness of basement ridges in A zone, C zone and E zone are relatively large, and the asymmetric amplitude of topography is~510 m,~410 m,~673 m, the asymmetric amplitude of crustal thickness is~2 km,~2.5 km,~1.1 km. We therefore suggest that B, D, and F have a relatively symmetric crustal structures, while A, C and E have an asymmetric crustal structures. According to the asymmetry of non-isostatic topography on conjugated flanks and compensation state of asymmetric topography, the asymmetry of A zone may due to uneven distribution of magma on conjugated flanks. The asymmetry of C zone and E zone may be caused by concentrated tectonism on one flank of basement ridge. We speculate that changes in the strike of ridge may facilitated the concentration of tectonism on one flank of the Gakkel Ridge.
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