摘要
南海东部次海盆的沉积记录蕴含着区域内中中新世以来沉积物的风化过程和演化历史信息.本文分析了国际大洋发现计划IODP 349航次南海东部次海盆U1431站位沉积物的主、微量元素和Sr-Nd同位素特征.研究显示,样品中化学风化蚀变指数为49~74,表明源区的化学风化强度为低到中等强度.沉积物在风化过程中以斜长石风化为主.含有火山碎屑的岩性单元Ⅵ和Ⅶ及55X-2层位受到含Fe、Mg矿物组分的物质来源输入影响,其余沉积物主要来自长英质源区.Sr和Nd同位素特征显示不同风化程度的沉积物源区具有明显差异.通过与周围潜在源区进行对比,推断12.8 Ma至今,U1431站位的物源主要来自珠江流域,印支半岛、吕宋和巴拉望提供了少量物质.其中12.5~7.4 Ma,沉积物源区受到周围岩浆活动形成的基性物质输入的影响,但仍以珠江源区为主. 6.5 Ma以后,台湾岛隆升剥蚀的陆源物质进入中央海盆.因此,台湾岛成为源区之一.
The sedimentary records of the east subbasin in the South China Sea reflect the weathering and evolution history of sediments since the Middle Miocene. We have analyzed the major, trace elements, and Sr-Nd isotopes of the sediments from the International Ocean Discovery Program(IODP) expedition 349 site U1431. The chemical weathering index of alteration(CIA) ranges from 49 to 74, indicating a low to moderate chemical weathering degree of the provenance. The chemical weathering trend shows the preferential leaching of plagioclase. The samples from units VI, Ⅶ and 55X-2 layer containing pyroclast are affected by the input of mafic materials, while the provenance of other samples is mainly felsic end-members. Sr and Nd isotopes show significant changes in the provenance of the sediments at U1431 site. By analyzing the Sr-Nd isotopic characteristics of sediments from U1431 site and surrounding potential provenance, we inferred the sediments at U1431 site were probably mainly from the Pear River and slightly from the Indochina Peninsula, Luzon and Palawan since 12.8 Ma.Several samples show positive εNdand low 86Sr/87Sr which may be related to the multiple volcanic activities in the study area during 12.5-7.4 Ma. After 6.5 Ma, the terrestrial material formed in the uplifting and erosion of Taiwan Island entered the central basin. Thus, Taiwan Island became one of the main sources.
作者
刘雪松
陈雪刚
孙凯
李春峰
Liu Xuesong;Chen Xuegang;Sun Kai;Li Chunfeng(Ocean College,Zhejiang University,Zhoushan 316021,China)
出处
《地球科学》
EI
CAS
CSCD
北大核心
2021年第3期1008-1022,共15页
Earth Science
基金
国家自然科学基金项目(No.41761134051)。
关键词
南海
东部次海盆
大洋钻探
沉积物
风化
物源
海洋地质
South China Sea
the eastern subbasin
ocean drilling
sediment
chemical weathering
provenance
marine geology
