Clay minerals in surface sediments of the South China Sea and

Source and transport of detrital fine-grained sediments in the northern South
China Sea and surrounding fluvial drainage basins
Zhifei Liu1*, Yulong Zhao1, Christophe Colin2, James T. Liu3, Chi-Yue Huang4, Khanh Phon Le5,
Fernando P. Siringan6, Chen-Feng You4, Kandasamy Selvaraj3, Shouting Tuo1, Zhong Chen7
1 State Key Laboratory of Marine Geology, Tongji University, Shanghai 200092
2 Laboratoire IDES, UMR 8148 CNRS, Université de Paris XI, Orsay 91405
3 Institute of Marine Geology and Chemistry, National Sun Yat-sen University, Kaohsiung, Taiwan 80424
4 Department of Earth Sciences, National Cheng Kung University, Tainan, Taiwan 70101
5 Faculty of Petroleum, Hanoi University of Mining and Geology, Hanoi
6 Marine Science Institute, University of the Philippines, Diliman, Quezon City 1101
7 South China Sea Institute of Oceanology, Chinese Academy of Sciences, Guangzhou 510301
* Corresponding author. Email:
This study reports clay mineralogy in surface sediments collected from both the South China Sea and
its surrounding major fluvial drainage basins to reveal sources of fine-grained detrital sediments and
their transport from source to sink, with a focus in the northern part. Total 225 surface samples
throughout the South China Sea and 223 surface samples from surrounding fluvial drainage basins (e.g.
Pearl River, Red River, Mekong River, southwestern Taiwan rivers and lakes, Luzon rivers, middle
Vietnam rivers, and northern Borneo rivers) were analyzed for clay minerals by X-ray diffraction
(XRD). Clay mineral assemblages derived from individual fluvial drainage basin present several
characteristic end-members. Rivers and lakes in southwestern Taiwan include dominantly of illite and
chlorite. Rivers in Luzon contain a huge amount of smectite. However, the Pearl River provides mainly
kaolinite, with moderate illite and chlorite. Northern Borneo clays also consist mainly of illite and
chlorite. The Red and Mekong Rivers present similar clay mineral assemblages with major illite,
chlorite, and kaolinite. However, rivers in middle Vietnam present abundant kaolinite with northern
rivers closer to the Red River. Despite of these characteristic end-member clay mineral assemblages in
the surrounding fluvial drainage basins, the surface distribution in the South China Sea is highly unified
with marginal clay mineral provinces close to relative fluvial drainage basins. But in the abysmal South
China Sea, clay minerals are highly mixed by both surface and bottom currents. The characteristic
end-members combined with illite crystallinity and chemistry index in the surrounding fluvial drainage
basins are sufficiently used to determine the sources of clay minerals in the South China Sea.
For the northern South China Sea, assuming that kaolinite is provided completely from the Pearl River,
the contribution of Taiwan in clay minerals is evaluated as 29% to the South China shelf and 23% to
the South China slope, respectively. Accordingly, the contribution of the Pearl River to the South China
shelf and slope is 52% and 31%, respectively. The Luzon Arc accounts for the rest of clay mineral
components mainly by providing smectite. The Bashi Strait-crossed branches of the southward deep
North Pacific Deep Water and the northward surface Kuroshio Current in the western Pacific may
transport Taiwan-sourced suspended sediments westwards to the northern South China Sea.