HR: 1340h
AN: V43C-1433    [Abstracts]
TI: Sulfur Isotopic Compositions of Sulfides From the Lower Huronian Supergroup, Ontario, Canada
AU: * Tachibana, S
EM: tachi@eps.s.u-tokyo.ac.jp
AF: Department of Earth and Planetary Science, University of Tokyo, 7-3-1 Hongo, Tokyo, 113-0033 Japan
AU: Hirai, T
EM: takemaru@eps.s.u-tokyo.ac.jp
AF: Department of Earth and Planetary Science, University of Tokyo, 7-3-1 Hongo, Tokyo, 113-0033 Japan
AU: Goto, K
EM: goto@eps.s.u-tokyo.ac.jp
AF: Department of Earth and Planetary Science, University of Tokyo, 7-3-1 Hongo, Tokyo, 113-0033 Japan
AU: Yamamoto, S
EM: yamashin.osachi@mx7.ttcn.ne.jp
AF: Department of Earth and Planetary Science, University of Tokyo, 7-3-1 Hongo, Tokyo, 113-0033 Japan
AU: Isozaki, Y
EM: isozaki@chianti.c.u-tokyo.ac.jp
AF: Department of Earth Science and Astronomy, University of Tokyo, 3-8-1 Komaba, Tokyo, 153-8902 Japan
AU: Tada, R
EM: ryuji@eps.s.u-tokyo.ac.jp
AF: Department of Earth and Planetary Science, University of Tokyo, 7-3-1 Hongo, Tokyo, 113-0033 Japan
AU: Tajika, E
EM: tajika@eps.s.u-tokyo.ac.jp
AF: Department of Earth and Planetary Science, University of Tokyo, 7-3-1 Hongo, Tokyo, 113-0033 Japan
AU: Shimoda, G
EM: h-shimoda@aist.go.jp
AF: Geological Survey of Japan, AIST, Central 7 Higashi 1-1-1, Tsukuba, 305-8567 Japan
AU: Morishita, Y
EM: y.morishita@aist.go.jp
AF: Geological Survey of Japan, AIST, Central 7 Higashi 1-1-1, Tsukuba, 305-8567 Japan
AU: Kita, N T
EM: noriko@geology.wisc.edu
AF: Geological Survey of Japan, AIST, Central 7 Higashi 1-1-1, Tsukuba, 305-8567 Japan
AU: Kita, N T
EM: noriko@geology.wisc.edu
AF: Department of Geology and Geophysics, University of Wisconsin, Madison, 1215 W. Dayton Street, Madison, WI 53706-1692 United States
AB: Mass-independent isotopic fractionation (MIF) of sulfur found in sedimentary rocks older than 2470 Ma implies that the atmospheric oxygen level was lower than 10$^{-5}$ PAL (present atmospheric level) in the Archean atmosphere [e.g., 1, 2]. Sulfides from the Rooihoogte and Timeball Hill Formations, Transvaal Supergroup, South Africa, (2316 Ma [3]) show only a small degree of MIF [4], which suggests that the atmospheric oxygen level reached 10$^{-5}$ PAL by 2316 Ma [4]. The Huronian Supergroup in E. Canada recording three Paleoproterozoic glaciatial events between 2450 and 2220 Ma is correlated with the Rooihootge and Timeball Hill Formations, and may record the evidence of the great oxygenation event. The sulfur isotopic compositions of sulfides in the Matinenda to Gordon Lake Formations of the Huronian Supergroup exhibit D$^{33}$S, deviation from a mass-dependent fractionation line, of less than 0.5 permil [e.g., 1]. This suggests that the atmospheric oxygen reached a level high enough to vanish the MIF signature before the Matinenda deposition. Here we report sulfur isotopic compositions of sulfides from the Livingstone Creek, Thessalon, and Matinenda Formations of the Lower Huronian Supergroup in the Elliot lake area. The Livingstone Creek and Thessalon Formations underlie the uraniferous Matinenda Formation. In-situ ion microprobe measurements showed that most of sulfides have a small degree of sulfur MIF, as seen in other formations, except for clastic sulfide blocks in the polymictic conglomerates of the Livingstone Creek Formation, the lowermost Huronian Supergroup. The sulfides in the Livingstone sulfide blocks show a clear evidence of MIF (D$^{33}$S = -1.7 to +3.6 permil) with d$^{34}$S of _|4 to +2 permil. The range of MIF from the sulfide blocks is an order of magnitude larger than that for other sulfides from the Huronian Supergroup. This indicates that the atmospheric oxygen may have started to increase after the formation of the sulfide blocks and before the deposition of the Livingstone Creek Formation. [1] Farquhar J. et al. (2000) Science, 289, 756. [2] Pavlov and Kasting (2002) Astrobiology, 2, 27. [3] Hannah J. L. et al. (2004) EPSL, 225, 43. [4] Bekker A. et al. (2004) Nature, 427, 117.
DE: 1040 Isotopic composition/chemistry
DE: 1610 Atmosphere (0315, 0325)
SC: Volcanology, Geochemistry, Petrology [V]
MN: 2004 AGU Fall Meeting