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综合利用洋脊轴部的深拖侧扫声纳资料和轴外的水深数据,研究了超慢速扩张的西南印度洋洋脊处洋壳增生过程的瞬时变化。在洋脊各段的侧扫声纳图像中可以观察到轴部火山洋脊的长度与高度的差异,及这些火山建造不同的变形程度。这些差异是由于轴部火山洋脊处于其生命演化周期的不同发育阶段,包括火山建造期和构造裂解期。利用轴外侧的水深数据确定了每个洋脊段中许多大小均匀的深海丘陵。这些深海丘陵均显示不对称的形状,面向轴部为陡峭的断层崖,背向轴部为平缓倾斜的火山岩斜坡。这些深海丘陵是被运移到两翼的、已被裂解的早期轴部火山洋脊的残留,它们形成于连续的岩浆建造期和构造裂解期之中,即一个岩浆—构造旋回。在厚地壳的洋脊区段观察到大型深海丘陵,而在薄地壳的洋脊区段观察到小型深海丘陵。这说明岩浆供给量控制着深海丘陵的大小。在薄地壳的洋脊区段,深海丘陵有规律地等间隔排列,表明岩浆—构造循环的伪周期性过程持续约0.4ma,比厚地壳的洋脊区段的周期时间短4～6倍。我们认为,有规律的深海丘陵样式与长寿命洋脊段下部几乎恒定的岩浆持续供给有关。相比之下,在岩浆供给急剧减少并极不连续的情况下,不再存在有规律的深海丘陵样式。
The instantaneous changes of oceanic crustal growth at the southwestern Indian Ocean ridges were studied by comprehensively using the data of deep-towed side scan sonar and the depth data outside the axis. Differences in the length and height of the volcanic ridge at the axis can be observed in the side-scan sonar images of the various segments of the ocean ridge, and the volcanoes are built to varying degrees of deformation. These differences are attributed to the fact that the volcanic ridge of the axis is at different developmental stages of its life cycle, including volcanic dating and tectonic rifting. Using the depth data on the outside of the shaft, many uniform deep deep hills in each ridges were identified. These deep-sea hills show an asymmetrical shape with a steep-sided cliff facing the shaft and a gentle-sloping volcanic slope on the back of the shaft. These deep-sea hills are the remnants of the early shaft volcanic ridges that have been moved to both wings and have been cracked. They formed during a continuous magmatic build-up and tectonic-lysis period, a magmatic-tectonic cycle. Large deep-sea hills are observed in the ocean ridge section of the thick crust, whereas small deep-sea hills are observed in the thin-crust ocean ridge sections. This shows that the supply of magma controls the size of deep-sea hills. In the thin crust oceanic ridge sections, the deep-sea hills are regularly arranged at equal intervals, indicating that the pseudo-periodic process of the magmatic-structural cycle lasted about 0.4 ma, which is 4 to 6 times shorter than that of the thick crust ridge. In our opinion, the regular pattern of deep-sea hills is related to the continuous supply of magma which is almost constant in the lower part of the long-lived ridge. In contrast, in the case of a drastic reduction and a very discontinuous supply of magma, there is no longer a regular pattern of deep-sea hills.