Figure Schematic representation for Se source and isotope fractionation from various mineralized processes (Image by IGCAS)

Over the past decade, as one of nontraditional stable isotopes, Se isotope has been developed rapidly and now becomes an important geochemical proxy to trace redox process and metal accumulation.  Some clues have indicated that the Se isotopic variation is important and related to metallogenesis key questions: the source of metals (hydrothermal or sea water), primary enrichment processes (direct selenide/sulfide precipitation or accumulation in organic matter) and late hydrothermal alteration/precipitation processes.

For the first time, Prof. WEN Hanjie from the Institute of Geochemistry, Chinese Academy of Sciences (IGCAS) and his co-worker, Dr. Jean Carignan from CRPG-CNRS of France have successful developed Se isotope system to trace the source and redox processes in the black shale-hosted Se-rich deposits.  Their study confirmed that Se isotopes are sensitive to redox reactions in natural environments.  Indeed, there is a strong relationship between Se isotopic variations and evidence for hydrothermal and supergene alteration/precipitation processes related to Se enrichment.  Hence Se isotopes may be used to further document redox reactions during sediments diagenesis or in the geological times, namely the Archean-Proterozoic transition, and those applications go well behind metallogenesis and metal cycling.

Those results titled “Selenium isotopes trace the source and redox processes in the black shale-hosted Se-rich deposits in China” have been published in Geochimica et Cosmochimica Acta (2011, V75, Pages 1411-1427).  The research was financed by the National Basic Research Program of China (Grant No. 2007CB411402), National Natural Science Foundation of China (Grant Nos. 40930425, 40773034 and 40873014).

(Provided by WEN Hanjie)