Geochemical surveys sampling

Levson, V.M. 2001. Regional till geochemical surveys in the Canadian Cordillera sample media, methods, and anomaly evaluation. In McClenaghan, M.B., Bobrowsky, P.T., Hall, G.E.M. Cook, S.J. (eds). Drift Exploration in Glaciated Terrain, Geological Society, Special Publication, 185, 45-68. 

A series of three workshops held in 2002 - 2004 included stakeholders representing about 50 North American governmental agencies, academia, environmental consultancies, and the medical community. The workshops resulted in a set of recommended sampling and analytical protocols for a soil geochemical survey that would meet the needs of this diverse set of customers. The Project is... 

We thank the many stakeholders who participated in the various workshops and provided valuable guidance in the design of the continental-scale soil geochemical survey. We also thank all the people who have, to date, participated in sampling in all three countries. 

Fig. 3. Distribution of catchments sampled for the National Geochemical Survey of Australia, as at 31 December 2008 (1078 catchments, or 78%, completed).

A national-scale geochemical survey of Australia is under way. It applies ultra low sampling density to transported and well-mixed outlet sediments, which are expected to represent the average composition of large catchments. The NGSA will provide the first complete, internally consistent geochemical data layer for Australia and is expected to find applications in energy and mineral resources exploration. 

In a random geochemical survey, Ce and Yb concentrations have been measured in twenty igneous samples. The results in ppm are reported in Table 4.5. Find the 95 percent bivariate confidence regions for the mean of (i) the Ce-Yb pair (ii) the Ce/Yb-Ce pair. 

Mineral exploration stream sediment geochemical survey data for the Otago region includes more than 2000 standard stream sediment samples from 19 surveys, more than 800 BLEG (bulk leach extractible gold) samples from 14 surveys and a few pan concentrate samples (MR reports). The stream sediment samples were typically analysed for Au and As, and... 

Key words (GeoRef Thesaurus, AGI) geochemical surveys, baseline studies, stream water, stream sediments, floodplains, overbank sediments, soils, humus, sampling, sample preparation, FOREGS, manuals, Europe... 

Plant, J. A. (1971). Orientation studies on stream sediment sampling for a regional geochemical survey in northern Scotland. Trans. Inst. Min. Metall. 80, 323-346. 

In the far east of Russia a eassiterite stockwork at a depth of 700 m lies between sandstone and aleurolite (Fig. 2-23). The results of the conventional geochemical survey and rock samples from trenches fail to reveal the position of the ore body (Fig. 2-23, curves A, B). The CHIM survey, however, gives a good expression with up to 16 pg Sn compared with a background of 0.5-1 pg (Fig. 2-23, curve C). This anomaly has a width of 250 m and practically coincides with the projection of the ore body to the surface. 

Figure 2-33 shows the results along a profile sampled at intervals of 5-20 m across known sulphide mineralisation in quartz veins in late Palaeozoic igneous rocks covered by 60 m of Quaternary sediments. Conventional geochemical survey data fail to detect the mineralisation (Fig. 2-33A). The MPF results, on the other hand, give well-defined anomalies for gold, arsenic, silver and copper (Fig. 2-33B).

There are a variety of sample collection and hydrocarbon analysis methods use in geochemical surveys for oil and gas deposits. In the case of free gas, samples are collected either in the atmosphere or, more usually, within the soil. For bound gas soil or rock is collected and the gas is liberated by one of several methods. In practice, however, it is rarely possible to determine solely free gas or solely bound gas. 

Soil samples are usually collected at the surface proper or at depths of up to several metres below the surface. As far as possible, samples are kept in their original condition until they are prepared for analysis in the laboratory. The analytical procedures are invariably partial extraction techniques. This approach has been widely used in other branches of exploration geochemistry, but assumes particular importance in gas geochemical surveys for petroleum. 

Jingbian is located in the central part of the Ordos Basin, where the oil and gas potential has long been considered to be poor because favourable structures are not evident in the seismic data. In 1988, however, the Changqing Oil Company proposed a scientific research well. This was preceded by a surface gas geochemical survey along several traverses, one of which passed through the site of the proposed well. The surface material, which is mainly aeolian sand, dry river-bank sediments and loess, was sampled at depths of 2-3 m at intervals of one km along traverse lines. At each sample site, Hg in... 

The Pinqiao oil field occurs in sandstone lenses of Triassic age, at a depth of less than 1000 m. A gas geochemical survey was carried out over a 1500 km area in order to test for microseepage from the known oil field and detect any neighbouring fields. Soil samples were collected on a 1 x 1 km grid and analysed by the acid treatment method for... 

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