本文基于采自西南印度洋中脊的表层生源沉积物样品,利用激光粒度分析方法测定了其粒级组成,分析了粒级分布特征及其原因。研究表明:西南印度洋表层生源沉积物平均粒径在3φ~8φ之间,分选差,其频率曲线发育单峰、双峰及多峰分布形式,它们与颗石、有孔虫壳体的粒径区间相对应;该区生源沉积物除了经历悬浮搬运和沉积外,还经受到来自南极底层流的推移方式搬运和改造作用。不同生物壳体的混合以及底层流的改造是制约该区沉积物粒级组成以及空间分布差异的主要原因。 Based on the samples of surface sediments from the mid-Southwest Indian Ridge, the grain-size composition of the sediments was determined by laser particle size analysis. The grain size distribution and its causes were analyzed. The results show that the average size of surface sediments in the southwestern Indian Ocean ranges from 3φ to 8φ, and the sorting is poor. The frequency curves of the sediments are unimodal, bimodal and multimodal. In addition to the suspended sediment transport and sedimentation, the source sediments of this area have been subjected to the transitional transport and transformation from the bottom flow in the Antarctic. The mixing of different biological shells and the reforming of the bottom flow are the main reasons that restrict the grain-size composition and spatial distribution of the sediments in this area.