Abstract: 257 surface sediment samples were collected from the western South China Sea (SCS),covering the shelf, slope to the deep sea basin, and analyzed for clay minerals. The results showed predominance by illite, with average content of more than 50% in the all area. The percentages of illite and smectite in clay minerals change much more significantly than those of chlorite and kaolinite. The illite content displays a distinctly positive relationship with that of smectite, while chlorite content is negatively related to that of kaolinite.
Based on the assemblages of clay minerals and their distribution, 4 provinces discriminated in the research area. Province A is characterized by very high content of smectite; the percentage of illite in Province B is lower than in Province A but th There is relative higher content of smectite and lower content in Province C,and lo of A, B, C and D were of illite and low content at of smectite is higher. wer content of illite and higher content of smectite, chlorite and kaolinite in Province D.
By a comparison with adjacent areas, the assemblage of clay minerals in Province A is more similar to that in Taiwan Strait and Yangtze River and in the estuary of the Pearl River and Hanjiang River. It is suggested that not only sediment from the southern China continent, but that from Taiwan Strait may pay an important role. The provenance of Province C should be mainly from the Indo-China Peninsula, as the assemblage of clay minerals is similar to that in the Vietnam Shelf. The provenance of the southern shelf and slope should include the Mekong River and Kalimantan Islands.