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Understanding Our Planet Through Chemistry

Element-Dispersion Halos

Another way of locating mineral resources is by identifying element-dispersion halos. Dispersion halos are abnormal levels of the metals that develop around deposits. This halo can extend for long distances from the deposit and, once recognized, can be used to trace down the source. The most familiar example of a halo is the dispersion of gold nuggets in drainages downstream from gold mother lodes.

Using today's technology, collected stream-sediment samples may be processed and analyzed for as many as 40 elements, giving an indication of very faint halos at some distance from a variety of deposit types. If elements of economic interest, such as gold, silver, copper, lead, or zinc, are present, they will be revealed in these analyses. This process is repeated for many samples until the entire study area is covered.

Photo of scientists in field with helicopter in background.By evaluating our nation's mineral resources, we can determine the appropriate use of Federal lands. Helicopters have little impact on the land and can be used in remote areas, such as Alaska, to efficiently gather samples for geochemical analysis. [104k]

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