摘要
XRD, TEM, SEM and EDS are employed to analyze smectites in the clay fraction of the surface sediments from the East Pacific. It is shown from the XRD results that the clay fraction consists of about 20% smectites.Three types of smectites are identified, Fe-rich (Type Ⅰ), Fe,Mg-rich (Type Ⅱ) and Na,Ca smectite (Type Ⅲ), and most of them are not well-crystallized. Type Ⅰ is widely distributed in sediments, showing honeycomblike in the SEM, and aggregated or dispersive hairlike, or cloudy assemblage with a bit curl near its edge in the TEM. This type is considered to be typomorphic type of authigenic smectite in the East Pacific. Type Ⅱ is similar to Type Ⅰ in micromorphology in the TEM, showing a transition micronite, while Type Ⅲ is tabletlike in the TEM with an unclear edge. Type Ⅰ may be altered from voleanics and some of them even precipitated from the low subthermal water. Type Ⅱ could also be formed in the ocean floor, while Type Ⅲ comes from dry and distant continental area. This study suggests that the characteristic of chemical composition and morphology of smectite may give a clue to understand sediment source, origin of minerals and sedimentation in the deep sea.
XRD, TEM, SEM and EDS are employed to analyze smectites in the clay fraction of the surface sedi- ments from the East Pacific. It is shown from the XRD re- sults that the clay fraction consists of ahout 20% smectites. Three types of smectites are identified, Fe-rich (Type Ⅰ ), Fe, Mg-rich (Type Ⅱ) and Na,Ca smectite (Type Ⅲ), and most of them are not well-crystallized. Type I is widely distrib- uted in sediments, showing honeyconlblike in the SEM, and aggregated or dispersive hairlike, or cloudy assemblage with a bit curl near its edge in the TEM. This type is considered to be typomorphic type of authigenic smectite in the East Pa- cific. Type Ⅱ is similar to Type Ⅰ in micromorphology in the TEM, showing a transition micronite, while Type III is ta- blellike in the TEM with an unclear edge. Type I may be altered from volcanics and some of them even precipitated from the low subthermal water. Type II could also be form- ed in the ocean floor, while Type III comes from dry and distant continental area. This study suggests that the char- acteristic of chemical composition and morphology of smec- tite may give a clue to understand sediment source, origin of minerals and sedimentation in the deep sea.
