Rare earth elements in seep carbonates as tracers of variable redox conditions at ancient hydrocarbon seeps
Rare earth elements in seep carbonates as tracers of variable redox conditions at ancient hydrocarbon seeps
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DOI：
10.1111/j.1365-3121.2008.00855.x
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发表时间：
2009-02
期刊：
影响因子：
2.4
通讯作者：
D. Feng;Duofu Chen;J. Peckmann
中科院分区：
文献类型：
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作者：
D. Feng;Duofu Chen;J. Peckmann
海洋油气渗漏是一个动态系统，典型地反映在这些地点形成的石灰岩的复杂岩性中。为了测试具有多代碳酸盐相的渗漏灰岩是否反映了可变的氧化还原条件，研究了五个古烃渗漏地点，Hollard Mound（中泥盆世）、Iberg（密西西比纪）、Beauvoisin（牛津纪）、峡谷和萨索普River（渐新世）以及Marmorito（中新世）灰岩的稀土元素（REE）模式。稀土总量变化范围很大（0.3-43.7 ppm）。早期微晶相往往比空间相关的后期相（微晶石、亮晶石和块状胶结物）显示出更高的含量。碳酸盐岩的页岩标准化稀土元素模式显示负和正Ce异常，即使对于个别矿床，这表明氧化还原条件变化显着。很明显，除了缺氧条件外，好氧条件在某些古渗漏环境中也很常见。间歇性氧合被认为是由液体流动的突然变化引起的。
Marine hydrocarbon seeps are dynamic systems, which are typically reflected in complex lithologies of limestones forming at these sites. In order to test if seep limestones with their multiple generations of carbonate phases reflect variable redox conditions, the rare earth element (REE) patterns of limestones from five ancient hydrocarbon‐seep localities, Hollard Mound (Middle Devonian), Iberg (Mississippian), Beauvoisin (Oxfordian), Canyon and Satsop River (Oligocene), and Marmorito (Miocene) have been investigated. The total REE contents vary widely (0.3–43.7 p.p.m.). Early microcrystalline phases tend to show higher contents than spatially associated later phases (microspar, sparite, and blocky cement). The shale‐normalized REE patterns of the carbonates show both negative and positive Ce anomalies even for individual deposits, suggesting that the redox conditions varied significantly. It is apparent that in addition to anoxic conditions, oxic conditions were common in some ancient seep environments. Intermittent oxygenation is presumed to have resulted from abrupt changes in fluid flow.