南海西南次海盆柱状沉积物酸类化合物的地球化学特征

南海西南次海盆是南海海盆中的一个重要构造单元，了解其沉积物的地球化学信息对于认识南海沉积环境至关重要。采用色谱质谱（GC-MS）方法对南海西南次海盆B3C和C7两个站位沉积柱中的酸类化合物进行研究，结果表明：①南海西南次海盆B3C和C7站位柱状沉积物中的正构脂肪酸呈偶奇优势分布，普遍以n-C16和n-C18为主；沉积物主要来源于浮游生物、藻类、细菌等，并有陆源高等植物的贡献。②B3C和B7沉积柱中酸类化合物来源主要以海源为主，总正构脂肪酸含量以及陆源优势正构脂肪酸（n-C24、n-C26、n-C28）、海源优势正构脂肪酸（n-C12、n-C14、n-C16）含量在垂向上分布较为稳定，变化波动小，表明该地区的大部分时期沉积环境较为稳定。③总脂肪酸（TFA）和TFA/TOC均表明该区域有机物积累普遍较低，且该处沉积区域处于非透光区和非热液区。

GEOCHEMICAL CHARACTERISTICS OF FATTY ACIDS IN THESOUTHWEST SUB-BASIN OF THE SOUTH CHINA SEA

The Southwest Sub-Basin is an important tectonic unit in the South China Sea. Geochemical information preserved in sediments is essential to the understanding of the sedimentary environment of the basin. In this paper, fatty acids in two sediment cores from the Southwest Sub-Basin were analyzed with GC-MS. The results suggest that: ①The n-fatty acids in the sediment columns B3C and B7 show an even-odd distribution pattern dominated by n-C16 and n-C18, sourced from vascular plants, soil materials, plankton, algae, and bacteria, contributed by both the terrestrial plants and marine diatoms. ②The acid compounds in the core sediments of B3C and B7 are dominated by marine sources. The content of total n-fatty acid and terrestrial dominant n-fatty acids (n-C24、n-C26、n-C28), marine-source dominated n-fatty acids (n-C12、n-C14、n-C16) vary slightly in the vertical direction, indicating that the sedimentary environment was rather stable for most of the time. ③Total fatty acids (TFA) and TFA/TOC ratio indicate that the accumulation rate of organic matter in this area is generally low, and the depositional area belongs to a non-transparent zone without hydrothermal activities.