HR: 1340h
AN: OS43A-0612    [Abstracts]
TI: Geological Characteristics of Active Methane Expulsion In Accretionary Prism Kaoping Slope Off SW Taiwan
AU: * Huang, C
EM: huangcy@mail.ncku.edu.tw
AF: Department of Earth Sciences, National Cheng Kung University, No. 1, University Road, Tainan, 701 Taiwan
AU: Chien, C
EM: r89224106@ntu.edu.tw
AF: Department of Earth Sciences, National Cheng Kung University, No. 1, University Road, Tainan, 701 Taiwan
AU: Yang, T F
EM: tyyang@ntu.edu.tw
AF: Department of Geosciences, National Taiwan University, No. 1, Sec. 4, Roosevelt Road, Taipei, 106 Taiwan
AU: Lin, S
EM: swlin@ntu.edu.tw
AF: Institute of Oceanography, National Taiwan University, No.1, Sec. 4, Roosevelt Road, Taipei, 106 Taiwan
AB: The Kaoping Slope off SW Taiwan represents the syn-collision accretionary prism characterized by active NW-trending folding - thrusting structures and high sedimentation rate favoring the formation of gas hydrate. For an assessment of gas hydrate potential in the Kaoping Slope off SW Taiwan, sedimentology, paleontology and geochemistry in box cores and piston cores were studied. BSRs are commonly found in seismic profiles in 400-600 m below seafloor of water depth 2500-1000 m. Active expulsions of methane were found along active thrust faults where sulfate/methane interface could be as shallow as 30 cm and the methane concentration of dissolved gases in bottom water and in pore-space of drilled core samples could be three-four order higher than the normal marine environments. Occurrences of authigenic carbonate and elongated pyrite tubes are correlated with shallow SMI depth and high methane content in bottom water and pore-space of sediment cores. Authigenic carbonates were found in seafloor surface and in 20-25 meters below seafloor. The authigenic carbonate nodules are characterized by irregular shape, whitish color, no visible microfossil, containing native sulfur, pyrites, gypsum, small open spaces, and very depleted carbon isotope (-54 ~ -43 per mil PDB). Tiny native sulfur and gypsum crystals were commonly found either on surface of foraminiferal tests and elongated pyrite tubes or in the authigenic carbonate nodules. Morphological measurements of elongated pyrite tubes show that they could represent pseudomorphs after three types of Pogonophora tube worm. Foraminifers are commonly filled by rhomboidal pyrites or cemented by pyrite crystals. Normal marine benthic foraminifers predominated by calcareous tests of slope fauna are associated with authigenic carbonate nodules in the study area, suggesting no major geochemistry effect on distribution of benthic foraminifers. Integrating sedimentology, paleontology and geochemistry characters, there could be high potential to have gas hydrate in the accretionary prism off SW Taiwan.
DE: 0463 Microbe/mineral interactions
DE: 0471 Oxidation/reduction reactions (4851)
DE: 1041 Stable isotope geochemistry (0454, 4870)
DE: 1051 Sedimentary geochemistry
DE: 3004 Gas and hydrate systems
SC: Ocean Sciences [OS]
MN: Fall Meeting 2005