富钴结壳显微构造与元素含量:基于中太平洋MHD79样品的研究

富钴结壳的壳层在形成过程中因环境不同而产生结构构造与物质成分的差异。选取采自中太平洋海山、具有多层构造的富钴结壳(样品号MHD79)进行分析。观察到其下部磷酸盐化壳层和上部未磷酸盐化壳层各有3层,即致密层、较致密层和疏松层,且其发育顺序呈镜像关系。元素化学分析显示:Sr、Pb含量由下到上表现为由高到低再到高,同样呈镜像分布,指示结壳生长过程中,古海洋生产力由高逐渐降低,又逐渐升高。在受强烈磷酸盐化作用影响的壳层中,由致密到疏松,其渗透性由弱到强,导致磷酸盐化由弱到强。在未受强烈磷酸盐化影响的壳层中,S i、A l、Ti、V元素含量与结壳显微构造的疏松或致密相关性不强,而是主要受控于结壳中包含的碎屑成分含量。由老到新S i、A l、Ti、V含量逐渐增加,可能是由于随着MH海山逐渐靠近亚洲大陆及青藏高原逐渐隆起,陆源物质供应逐渐增加的结果。

Microstructure and Element Abundance of Co-rich Crust: Evidences from the Layered Sample MHD79 Collected from the Central Pacific

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.