Abstract:

Because of different formation environments, microstructure and elements content of each layer in Co-rich crust must have alterations. Based on studies of relation between microstructure and elements content of each layer in Co-rich crust, this paper discovers that the relations might contribute to find out the forming mechanism and environment of the crust.  We selected a Co-rich crust sample(MHD79), which has multi-layer structure and was gathered from central Pacific MH seamount. In the MHD 79 sample, both lower phosphatization crust and upper non-phosphatization crust have three layers, such as dense layer, sub-dense layer and porous layer; and the relation between the growing orders of lower phospharization crust and upper non-phosphatization crust are mirror-image. From bottom to top, contents of Sr and Pb are from high to low, and then to high, also display mirror-image. These indicate that marine paleoproductivity is from high to low, and then to high in crust growth process. In phosphatization layers, from dense to loose, the permeability of layers is then raised from weak to strong, which lead to phosphatization of layers from weak to strong. In non-phosphatization layers, the contents of Si, Al, Ti and V are not relative to looseness or denseness of microstructure, but relative to the contents of decrial component. From old layers to new layers, the contents of Si, Al, Ti and V are gradually increased; this result may be caused by increases of terrigenous sediment with MH seamount close to Asian continent and the gradual uplifting of Qinghai-Tibet plateau.

Key words: central Pacific, Co-rich crust, microstructure, element content