Journal of Tropical Oceanography ›› 2017, Vol. 36 ›› Issue (2): 48-59.doi: 10.11978/2016060CSTR: 32234.14.2016060

• Orginal Article • Previous Articles     Next Articles

Genetic types and elemental occurrence phases of ferromanganese nodules in the northern South China Sea

Yi ZHONG1,2(), Zhong CHEN1(), Aibin MO1,2, Yun LUO1,2, Gang LI1, Xufeng ZHENG1   

  1. 1. Key Laboratory of Marginal Sea Geology, South China Sea Institute of Oceanology, Chinese Academy of Sciences, Guangzhou 510301, China
    2. University of Chinese Academy of Sciences, Beijing 100049, China
  • Received:2016-06-23 Revised:2016-09-01 Online:2017-03-20 Published:2017-04-06
  • Supported by:
    National Natural Science Foundation (41376057, 41676056, 41306047)

Abstract:

To understand the elemental occurrence phases and the origin of ferromanganese nodules in the northern South China Sea, selective leaching techniques have been utilized to study the geochemical phases (viz. carbonate, Fe-Mn oxide and residual) of ferromanganese nodules on the upper continental slope and the lower continental slope, as well as in the deep-sea basin. According to the Fe-Mn-(Cu+Co+Ni) diagram, Fe-Mn nodules around the Dongsha Islands are associated with hydrocarbon seeps. Nodules on the lower continental slope and in the deep-sea basin have a similar formation mechanism, and are both hydrogenous in origin. K, Ca, Na, Mg, and Sr are mainly enriched in the carbonate phase; Fe, Mn, Ni, Cu, Zn, and Pb are mainly concentrated in the Fe-Mn oxide phase; Al, Ti and Mo are mainly concentrated in the residual phase. The variation of elemental occurrence phases is influenced by multiple factors. The strength of biological productivity and the dilution of calcareous bioclast material can result in change of carbonate phase of Fe-Mn nodules. On the lower continental slope and in the deep-sea basin, REEs and yttrium are mainly associated with the Fe-Mn oxide phase. However, the carbonate and residual phases of hydrogenous oxides have extremely low REE content. The REE origins in carbonate phases of Fe-Mn nodules from different areas are basically similar. The Fe-Mn nodules in the slope area and deep-sea basin have identical residual phase distribution of REEs and yttrium except for the upper slope area. It is probably influenced by residual sources and redox environment of the Fe-Mn nodules. This study discusses the elemental chemical phases in Fe-Mn nodules in the northern South China Sea and provides important basic data for the resources evaluation in this area in the future.

Key words: ferromanganese nodule, occurrence phase, genetic type, distribution pattern, northern South China Sea

CLC Number: 

  • P736