Iron isotopes formation

Alexander CMOD, Grossman JN, Wang J, Zanda B, Bourot-Denise M, Hewins RH (2000) The lack of potassium-isotopic fractionation in Bishunpur chondrules. Meteor Planet Sci 35 859-868 Alexander CMOD, Wang J (2001) Iron isotopes in chondrules implications for the role of evaporation during chondrule formation. Meteor Planet Sci 36 419-428... 

Frankenberger Jr. WT, Engberg RA (eds), Marcel Dekker, New York, p 281-296 Lyons TW (1997) Sulfur isotopic trends and pathways of iron sulfide formation in upper Holocene sediments of the anoxic Black Sea. Geochim Cosmochim Acta 61(16) 3367-3382... 

Alexander CMO D, Wang J (2001) Iron isotope in chondrules implications for the role of evaporation during chondrule formation. Meteoritics Planet Sci 36 419-428... 

Figure 19. Iron isotope fractionations between magnetite and Fe carbonates from adjacent bands in Banded Iron Formations (Johnson et al. 2004a), compared to Fe(II)aq sources and Fe pathways inferred from the Fe isotope fractionations given in Table 3. values are as measured, and the scales for...

The extreme negative values for the carbon isotope shifts (up to around 5-60 in some of the banded iron(ll)-formations), strongly indicate that microbial processes were involved in the formation of these deposits (Canheld et al. 2000). One explanation of the low values is that the bacteria involved could have used carbon sources that were already metabolized, e.g., by methanogens, and thus already had undergone a significant isotope shift (i.e., 5 values for methane are already negative however, the values for the associated C02/carbonates are positive, between -i-5 to -i-15%o) (Coleman et al. 1993 Horita and Berndt 1999). 

Poitrasson F., HalUday A. N., Lee D.-C., Levasseur S., and Teutsch N. (2003) Iron isotope evidence for formation of the Moon through partial vaporisation. In Lunar Planet. Set XXXIV, 1433. The Lunar and Planetary Institute, Houston (CD-ROM). 

FIGURE 5.18 Schematic model for the formation of Archaean banded iron formations, showing the constraints imposed by iron isotope studies (modified from Johnson et al., 2003). 

Horn, I., von Blanckenburg, F., Schoenberg, R., StEINHOEFEL, G. MaRKL, G. 2006. In-situ iron isotope ratio determination using UV-femtosecond laser ablation with application to hydrothermal ore formation processes. Geochimica et Cosmochimica Acta, 70, 3677-3688. 

Iron isotopes constrain biologic and abiologic processes in banded iron formation genesis. Geochim. Cosmochim. Acta, 72 (1), 151-169. 

In a preliminary report (2), Fe atoms were reacted with O2, leading to formation of FeiO ), a cyclic isosceles (C2v) species, as suggested by mixed isotope experiments. Reaction of Fe atoms with N2O resulted in formation of FeO. A feature at 887 cm, assigned to a Fe/Nj complex, is probably erroneous, and may be an iron nitride species. In the same triad, the MCD spectrum of matrix-entrapped OSO4 was studied (46). The spectrum was found to be similar to that of Mn04 in a solid lattice, and was assigned accordingly. 

This discovery was quite unexpected, since iron oxide has been never reported as an active catalyst in either partial or full oxidation. The studies of two simplest reactions, i.e. O2 isotopic exchange and N2O decomposition, revealed a dramatic change of Fe properties in the ZSM-5 matrix compared to Fe203 [4]. Fe atoms lose their ability to activate O2 but gain remarkably in their ability to activate N2O. It gives rise to a great effect of the oxidant nature in the reaction of benzene oxidation over the FeZSM-5 zeolite (Table 1). Thus, in the presence of N2O benzene conversion is 27% at 623 K, while in the presence of O2 it is only 0.3% at 773 K. And what is more, there is a perfect change of the reaction route. Instead of selective phenol formation with... 

Becker RH, Clayton RN (1976) Oxygen isotope study of a Precambrian banded iron-formation. Hamersley Range, Western Australia. Geochim Cosmochim Acta 40 1153-1165 Beard BL, Johnson CM (2004) Fe isotope variations in the modem and ancient earth and other planetary bodies. Rev Mineral Geochem 55 319-357... 

Figure 2. Co-variation of Fe/ "Fe and Fe/ "Fe ratios of individual layers from Banded Iron Formations, modified from Johnson et al. (2003a). The horizontal axis shows isotopic compositions in 5 Fe (bottom) and Fe (top), and the vertical axis shows values in d Fe (left) and s Fe (right). Point A has a d Fe of +1.00%o, which corresponds to an s Fe value of +15.0. Figure illustrates the multiple ways in which the same Fe isotope composition may be reported when isotopic variations are due to mass-dependent processes. See text for discussion.

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