Abstract Satellite images have been widely used to characterize mineral alteration zones in surface rocks affected by hydrocarbons' upward seepage. Likewise, magnetic surveys over oil fields have been employed for similar purposes. This work integrates satellite image spectral analyses with rock magnetic and geochemical data (i.e., mass-specific magnetic susceptibility χ, saturation isothermal remanent magnetization SIRM, analysis of SIRM acquisition curves, absorption spectro-radiometry, and X-ray diffraction analyses). The target area was an oil-prospective region in northwestern Venezuela (Falcon Basin) swarmed by hydrocarbon seeps. The study's main goal was to depict the spatial extension and vertical reach of the hydrocarbon-mediated alteration produced by these seeps and gain some knowledge about the processes involved in the subsequent mineral changes. Multispectral and hyperspectral satellite images showed three hydrocarbon-induced diagenetic anomalies (HIDAs) associated with undifferentiated clays and kaolinite, and low dolomite content. A simple weathering model was suggested combining the likely effects of the ascending seepage of oil and gas with the seasonal alternation of leaching and evaporation of meteoric waters. This model explains the magnetic enhancement with depth due to Fe oxides and sulfides' formation by reducing and oxidizing events. A non-supervised Two-Step Cluster Analysis (TSCA) was applied to integrate geochemical and rock magnetic properties with satellite images. The input variables were log SIRM and proxies of undifferentiated clays and dolomite concentrations obtained from the band-ratio ASTER images. The TSCA yields three clusters associated with different alteration levels in the top and low (0.3–1 m) soils and sediments. By mapping the class membership of each sampling site, for both depth levels, it was possible to obtain a broad view of the synergistic change of these combined properties, not only over the whole extent of the study area but also from top to bottom of the weathered sequence. This case study illustrates the potential of such an integrated method as an oil exploration tool, and a means to assess the level and scope of the environmental impact produced by hydrocarbon seepage on terrestrial ecosystems.

中文翻译：

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以卫星图像光谱分析和岩石磁数据为特征的油气渗漏表面表现（委内瑞拉西部的 Falcon 盆地）

摘要 卫星图像已被广泛用于表征受油气向上渗流影响的地表岩石中的矿物蚀变带。同样，对油田的磁测量也被用于类似的目的。这项工作将卫星图像光谱分析与岩石磁性和地球化学数据（即特定质量的磁化率 χ、饱和等温剩磁 SIRM、SIRM 采集曲线分析、吸收光谱辐射测量和 X 射线衍射分析）相结合。目标区域是委内瑞拉西北部（猎鹰盆地）的一个石油勘探区，那里充满了碳氢化合物渗漏。研究' 的主要目标是描绘由这些渗漏产生的碳氢化合物介导的蚀变的空间延伸和垂直范围，并获得有关随后矿物变化过程的一些知识。多光谱和高光谱卫星图像显示三个碳氢化合物诱导的成岩异常 (HIDA) 与未分化的粘土和高岭石以及低白云石含量有关。提出了一个简单的风化模型，将石油和天然气上升渗流的可能影响与大气水浸出和蒸发的季节性交替相结合。该模型解释了由于通过还原和氧化事件形成 Fe 氧化物和硫化物而导致的磁性随深度增强。应用非监督两步聚类分析 (TSCA) 将地球化学和岩石磁性与卫星图像相结合。输入变量是对数 SIRM 和从带比 ASTER 图像获得的未分化粘土和白云石浓度的代理。TSCA 产生三个与顶部和低层（0.3-1 m）土壤和沉积物的不同蚀变水平相关的聚类。通过绘制每个采样点的类成员关系，对于两个深度级别，可以广泛地了解这些组合属性的协同变化，不仅在整个研究区域范围内，而且从顶部到底部风化序列。本案例研究说明了这种综合方法作为石油勘探工具的潜力，