HR: 1340h
AN: B53B-0999    [Abstracts]
TI: Biomarker Record From the Tisdale Group (2707 - 2705 Ma) and Porcupine Group (2685 - 2673 Ma) of the Abitibi Subprovidence, Timmins, Ontario, Canada
AU: * Ventura, G T
EM: gventu1@uic.edu
AF: Department of Earth and Environmental Sciences, University of Illinois at Chicago, 845 W. Taylor St. , Chicago, IL 60607-7059 United States
AU: Kenig, F
EM: fkenig@uic.edu
AF: Department of Earth and Environmental Sciences, University of Illinois at Chicago, 845 W. Taylor St. , Chicago, IL 60607-7059 United States
AB: Saturated/unsaturated and aromatic hydrocarbon fractions extracted from greenshist facies metasedimentary greywackes, siltstones, and shales of the Tisdale (2707-2705 Ma) and Porcupine Group (2685-2673 Ma) of the Abitibi Subprovince, Ontario Canada were analyzed for biomarkers. Core and hand samples were obtained from three mines run by Porcupine Joint Ventures and the core library at the Ministry of Northern Development and Mines, Timmins, Ontario. Tisdale Group sedimentary facies were previously interpreted as laminated massive sulfide and/or interflow sediments interstratified by subaqueous komatitic-tholeiitic flows. Porcupine Group turbidite facies were interstratified by massive, brecciated alkaline lava flows and reworked volcaniclastic facies. All Porcupine Group samples contained primary depositional fabric. Biomarker maturity calculations indicate the sediments are mature and either reached or surpassed oil generation. All samples contained hopanes C$_{27}$ 22,29,30-trisnorhopane-II (Ts & Tm), C$_{29}$ $\alpha$$\beta$-30-norhopane, C$_{29}$ 18$\alpha$-30-norneohopane, C$_{30 }$ $\alpha$$\beta$ hopane, C$_{30}$ $\beta$$\alpha$- hopane, and C$_{31}$-C$_{35}$ (22S & R) homohopanes. Most samples contained C$_{27}$-C$_{29}$ (20S & R) $\beta$$\alpha$ diacholestane, C$_{27}$-C$_{29}$ $\alpha$$\beta$$\beta$ cholestane (20S & R), C$_{27}$-C$_{29}$ $\alpha$$\alpha$$\alpha$ cholestane (20S & R), and 4-methyl steroids. Tricyclic terpanes ranging from C$_{19}$-C$_{29}$, but were not present in all samples. Biomarkers from the Tisdale Group samples are similar to those found in modern hydrothermal systems and include unresolved complex mixtures, abundant branched alkanes with quaternary carbon atoms, alkyl-cyclohexanes (C$_{16}$-C$_{29}$ with strong odd over even dominance), alkyl-cyclopentanes (C$_{16}$-C$_{29}$) containing only even carbon number homologs), and C$_{37}$-C$_{40}$ acyclic and cyclic archeal isoprenoids. Biomarkers from the Porcupine Group samples include C$_{16}$-C$_{35}$, branched alkanes, C$_{16}$-C$_{29}$ alkyl-cyclohexanes and alkyl-cyclopentanes (with no carbon number preference). Aromatic fraction for this group were generally low and included mono, di, and trimethyl naphthalenes, phenanthrenes, and aryl-isoprenoids. Several of these samples also contained abundant C$_{37}$-C$_{40}$ acyclic and cyclic archeal isoprenoids. The diversity of biomarkers within these two stratigraphic groups suggests that the hydrocarbons are syngenetic with their host rock and represent a change in depositional environments from that of a sulfidic hydrothermal vent system to one later overlain by continental shelf sediments.
DE: 9350 North America
DE: 9619 Precambrian
DE: 1055 Organic geochemistry
DE: 0400 Biogeosciences
SC: Biogeosciences [B]
MN: 2004 AGU Fall Meeting