Selenium isotopes trace the source and redox processes in the black shale-hosted Se-rich deposits in China

Selenium isotopes trace anoxic and ferruginous seawater conditions in the Early Cambrian

“…Fe oxides), ensuring that most fresh samples were obtained in these two sections. The characteristics of these samples have been described in Wen and Carignan (2011) and Fan et al (2011Fan et al ( , 2013. Samples from the Silikou section have been studied in detail in terms of mineralogy and petrology (Chang et al, 2010(Chang et al, , 2012.…”

“…The analytical process for Se isotopes has been detailed described by Wen and Carignan (2011). Briefly, Chemical purification of Se for isotopic measurements used the Thiol Cotton Fibre (TCF) method (Marin et al, 2001;Rouxel et al, 2002) for which Se recovery is N98%.…”

“…For unweathered (fresh) black shale samples, the mean δ 82 Se value is − 0.30 ± 1.01‰ with a mean Se concentration of 77 ± 3.49 ppm; however, weathered samples yield a δ 82 Se value of 3.98 ± 3.90‰ and mean Se concentration of 716 ± 1670 ppm. The largest range of Se isotopic composition for a single sedimentary formation is reported in the Yutangba Se deposit, where supergene alteration has produced a fractionation of~23‰ (Wen and Carignan, 2011;Zhu et al, 2014). It appears that in most cases only secondary alteration (weathering, diagenesis) can lead to a greater isotopic fractionation and Se enrichment.…”

Analysis of mass dependent and mass independent selenium isotope variability in black shales

“…It is alternatively possible to correct for ArAr by measuring the 80 Se-corrected 40 Ar 40 Ar beam, and using this to calculate the other ArAr beams. 5,17 However, this method would require an appropriate functional relationship between 40 Ar 40 Ar and the other dimers; an assumption of an exponential mass dependent relationship as used for elemental species might be the most obvious. Although the exponential form is widely used for inter-relating atomic species its effectiveness for dimers is not well documented and need not necessarily be similarly appropriate.…”

Selenium Behavior in San Francisco Bay Sediments

“…Positive correlations between solid phase total selenium and organic carbon are normally found in marine sediments (Sokolova and Pilipchuk 1973;Belzile and Lebel 1988;Wen and Carignan 2011). These positive correlations can be explained by the actual incorporation of selenium into organic matter (e.g., seleno amino acids in proteins of phytoplankton ;Wrench 1978;Fan et al 2002) and subsequent flux to underlying sediments.…”