Field Methods in Regional Geochemical Surveys

Geochemical studies vary enormously in an area. At one extreme, they cover  

Studies at different scales differ considerably in the way they are carried out. Not only sampling density, but sampling material, sampling depth, analytical methods, and data processing also essentially depend on the aim of the study, the size of the area to be studied, the objects to be recognized, and the contrast between the anomaly and the surrounding area. The sources of the anomalies detected by different sampling densities are also totally different in nature. 

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Gas geochemical surveys of light molecular-weight hydrocarbons (C1-C5) and Hg have proved to be useful methods of detecting oil and gas fields in the Ordos Basin of northern China and of indicating potential oil or gas fields in the Lixian Depression of southern China. The annular anomaly is the type most usually found in these regions, although apical and linear anomalies occur under particular conditions. 

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