Different occurrence of selenium in kerogen: TEM evidence
WEN Han jie, QIU Yu zhuo, LIU Shi rong(Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550002, China)
The Laerma Se Au deposit and Yutangba Se deposit are two important deposits found recently in China. Se is closely related to the kerogen, and about75%selenium is enriched in the kerogen in the Laerma Se Au deposit and about 65.8%selenium enriched in the kerogen in the Yutangba selenium deposit. The results of the Transmission Electron Microscope (TEM) observation show that the occurrence of Se in the kerogen is completely different in the two deposits. Se occurs mainly in the form of ultramicro inclusion native Se in the Yutangba Se deposit. A lot of native selenium has been identified in samples of kerogen from the Yutangba Se deposit, which is adhered or wrapped in the sandwich, crannyor pore space of the kerogen, usually presented with the amorphous shape. However, there is no native selenium found in the kerogen from samples of the Laerma Se Au deposit. The observation of TEM and analysis of EDS suggest that selenium may be organic bonded and probably form covalent bonds with oxygen bearingradicals or combines with organism by substituting for sulfur. There are two direct factors for notion about the difference of occurrence of Se, that is sulfurcontent in the kerogen and the condition of redox. The potential significance of TEM EDS study is summarized and it is suggested that TEM EDS is a kind of effect method to study the occurrence of element in kerogen.