A New-Type Polymetallic Nodules from Northwest Continental Margin of the South China Sea and its Causative Mechanism

Abstract

The polymetallic nodules are collected from the South China Sea (SCS) in the northwest continental margin of China. Two selected samples among the various morphological types were used for the laboratory analysis of physical properties, mineralogy, geochemistry and chronology. According to the data, these samples show lower ratio of Mn/Fe(0.73). They are rich in Fe, Si, Al, ?REE, and poor in Mn, Cu, Co and Ni. The chronology contrasts calcareous nannofossil biostratigraphy and Beryllium (Be) isotope mass spectrum method, and the growth rate of the polymetallic nodules were confirmed about 7.87 to 74 mm/Ma. This rate is faster than the generic oceanic nodules and other marginal sea nodules. These nodules may represent new-type ones which grow fast in high deposition velocity environment from the northwest continental margin of the SCS. The reason of the fast growth may be affected by the environmental fluctuations and the change of terrigenous sediments.