Distribution of clastic minerals of surface sediments in the western China Sea and their provenance

Abstract：The provenance of sediments in the western South China Sea (SCS) is less studied,and especially there is much dispute about the provenance of the central part of the sea area. Because of the absence of large river input,it is usually considered that the main material sources of the central part are the Red River in the north and the Mekong River in the south. In order to better understand the provenance in the western SCS,systematic surface sediment samples were collected and clastic minerals were analyzed. The results show that clastic minerals are mainly distributed in the continental shelf in the south and the slope in central part. Factor analysis shows that the south,central and north areas may be distinguished for the clastic minerals in the western SCS. The clastic minerals in the shelf of the south area consist predominantly of heavy minerals such as rutile,anatase,leucoxene,zircon,tremolite and staurolite and light minerals such as quartz,feldspar,which indicates that the protoliths are dominantly magmatic rocks and partly metamorphic rocks; those in the slope of the central area are mainly staurolite,tremolite,tourmaline,limonite,biotite and muscovite,which suggests that the protoliths might be mainly metamorphic rocks; and the clastic minerals in the slope of the north area are scarce and the characteristics of the mineral assemblage are not pronounced. The three areas not only show notably different mineral assemblage characteristics but also distinct boundaries between the areas,indicating that their provenances are markedly different. The provenance in the south area is the Mekong River and Kalimantan; the clastic mineral assemblage in the central area is in the main coincident with the metamorphic rocks exposed in large amount in the Indo-China Peninsula,suggesting that the provenance is mainly the Indo-China Peninsula rather than the Mekong River south of it and the Red River north of it.