The distribution characteristics of rare metal elements in surface sediments from four coastal bays on the northwestern South China Sea

Abstract

The distribution of rare metal elements (Zr, Sn, Ti, Y, Nb, Ta, Ce, La, Nd and Th) in surface sediments from four bays along the northwestern coast of the South China Sea allowed infer their main controlling factors and their mineralization potential as metals placer. The results revealed that their contents in surface sediments are very variable but show a clear geographic regularity. The average content of all elements in those areas decreases from the East to the West, with the minimum value of all elements in Leizhou Bay, the maximum value of Zr, Y, La, Ce, Nd and Th in Zhanjiang Bay, and the maximum values of Sn, Ti, Nb and Ta in Hailing Bay. The relative enrichment of these elements in two easternmost bays (Hailing Bay and Shuidong Bay) are attributed to the southwest alongshore current, which drain and transport terrigenous sediments from the granite region of the South China into these two bays. The correlation results between all element contents and fine sediment fraction (<63 μm) suggested that the main factors controlling the distribution of Ti, Nb and Sn should be the fine fraction of the sediment, but alternatively Zr, Y, La, Ce, Nd and Th are rich in heavy minerals and/or bioclasts, and Ta maybe affected by both. Detail analysis shows that sediments from Hailing Bay may contain abundant zircon, cassiterite, ilmenite (or rutile), xenotime, monazite, niobium tantalite and other rare metal minerals, with a good prospect as a rare metal placer resource, and the zircon, xenotime and monazite may also have good metallogenic prospects in Shuidong Bay and in the local area of Zhangjian Bay.