Microstructure and Fossilized Bacteria in Seep Carbonates from An Active Gas Vent in Green Canyon Block 238 of Gulf of Mexico
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摘要: 采于墨西哥湾GC238海底天然气渗漏区浅表层的冷泉碳酸盐岩呈结核状产出，由方解石微晶和胶结物及少量的黄铁矿构成。胶结物由直径为0.1～0.5 m的方解石化的球体、卵形体、棒状体组成，充填于方解石晶体之间。冷泉碳酸盐岩结核下表面发育有由方解石化的球体、卵形体、棒状体组成的薄层，其中的一些球状集合体（约5 m）断面显示发育有核和外壳的层圈结构。黄铁矿呈草莓状，也具有相似的层圈结构。这种层状结构与活体古细菌被硫酸盐还原细菌包裹的层圈结构相似。样品中所保存的球体、卵形体、棒状体及其所组成的层圈结构可能是石化的甲烷氧化古细菌和硫酸盐还原细菌。Abstract: Seep carbonate were collected in an area actively seeping methane in the Green Canyon Block 338 of Gulf of Mexico, which is composed of microcrystalline calcite, cement and pyrite framboid. The cement is composed of speroidal, oval, and rodshaped particles ~0.1 to 0.5 μm in diameter that filled the pores between the calcite crystals. The underside of the carbonate crusts occurs a microlayer consisted of ball, worm, rodshaped calcite particles. The larger ball (~5μm) in the microlayer has a distinct cores surrounded by an outer shell which both consists of smaller calcite particles. Pyrite framboids are also arranged in an inner core surrounded by an outer layer. These layeredstructure characteristics of the carbonate balls and the pyrite framboids are similar with living colonies of methane oxidizing archea (MOA) and sulfate reducing bacteria (SRB). The speroidal, oval, and rodshaped particles and layeredstructure in the carbonate crusts suggest that these could be fossilized MOA and SRB bacteria.
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