Microstructure of the Si-Fe-Mn oxide from the PACNANUS hydrothermal field and its implications

With optic microscope,electronic probe and scanning electron microscope analytical methods,the mi-crostructure of the Si-Fe-Mn oxide,which had been collected by trawl during the expedition of "KX08-973" on the PACMANUS hydrothermal field,Eastern Manus Basin,in 2008 was analyzed.The Si-Fe-Mn oxide exhibited cryptocrystalline texture under optic microscope;and fossilized diatoms were found under scanning electron mi-croscope.The electronic probe results revealed that the distributions of Fe and Mn were zoned and manifested the characteristics of Si-Mn layer enveloped by Si-Fe layer,reflecting a multi-staged formation of the Si-Fe-Mn oxide.The Si-Fe-Mn oxide was a result of direct precipitation of low temperature hydrothermal fluid,which rich in Si,Fe and Mn.This study will facilitate further research of Si-Fe-Mn oxide in this hydrothermal field,such as the com-bining of Si with Mn and Fe in the Si-Mn layer and Si-Fe layer and the role of the microbes during the forming of the Si-Fe-Mn oxide.