中文摘要：

慢速-超慢速扩张西南印度洋中脊普遍发育转换断层,洋脊分段性明显,是研究地质构造与地幔部分熔融关系的理想场所。对西南印度洋中脊（52°20′53°30′E）Gallieni转换断层与Gazelle转换断层之间洋脊段6个站位的深海橄榄岩研究发现：尖晶石Cr#的变化范围为0.194～0.329,对应的地幔部分熔融程度为7.6%～13.0%,反映全球洋中脊系统中低程度的地幔部分熔融,并且离转换断层近的地幔部分熔融程度低于洋脊分段中心,这种差异除了受转换断层的冷却作用影响外,还可能与洋脊分段中心更强的岩浆抽提作用有关。将研究区与全球其他洋脊对比发现,尖晶石Cr#及对应的地幔部分熔融程度随洋脊扩张速率的降低而降低,在探讨地幔部分熔融程度与洋脊扩张速率的相关性时,通过对转换断层效应的校正,能够更准确地反映地幔部分熔融程度随洋脊扩张速率的变化趋势。

英文摘要：

Slow-ultraslow spreading Southwest Indian Ridge （SWIR） is an ideal place to study the relationship between geological structure with mantle partial melting due to the presence of abundant transform faults and segmenting the ocean ridge. Studies on abyssal peridotites from 6 dredges in the ridge segment between the Gallieni transform fault （TF） and Gazelle TF in SWIR reveal that the Cr of spinel ranges from 0. 194 to 0. 329, corresponding to the degree of mantle partial melting from 7.6% to 13.0% which is very low in the global oceanic ridge. The degree of mantle partial melting is controlled by transform fault and the enhanced melt extraction in the segment center, which is shown as greater degree of mantle partial melting in the ridge segment center than near the transform fault. Comparison of the studied area with other ridges shows that both the Cr values of the spinel and the degree of mantle partial melting decrease with the decrease of ridge spreading rate. The relationship between mantle partial melting and ridge spreading rate will be estimated more accurately after the correction of the transform fault effect.