Geological Survey professional paper Volume 907, pts. 1-2

9781236380272: Geological Survey professional paper Volume 907, pts. 1-2

This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. Excerpt: ...a study of the source of the secondary metals associated with stream sediments. Present information suggests that where metal-rich interstitial ground water flows into a stream from bank soil, there are abrupt changes in the physical and chemical environment. These changes cause the metals to precipitate in the stream, either as grain coatings or as small nodules, before they are transported very far downstream. Most of the cold-extractable metals found in stream sediments are thought to have been derived from these interstitial ground waters, even though stream waters usually constitute a much larger proportion of the total water volume at a given stream locality (G. A. Nowlan, oral commun., 1973). As was mentioned in the section on soil surveys, the optimum size of material, in this case streamsediment material, used for analysis should be determined in any new area. Most, but not all, elements are concentrated in the sediment fines; however, the best grain size to retain for analysis should be the one that provides the best anomaly contrast. Hawkes and Webb (1962, p. 256-258) have given an excellent discussion of this problem. Most stream-sediment surveys have used the finegrained (-80 mesh) fraction for analysis; however, Fisher (1970) reported that in some areas of Australia, stream-sediment material as coarse as a-20 to +40 mesh fraction gave better results than did standard-80 mesh fractions. Different climatic, geologic, and terrain conditions were found to influence the metal content of different size fractions. The importance of selecting the proper size of sample material to use in a stream-sediment survey was also emphasized by Erickson, Marranzino, Oda, and Janes (1966). Their study was conducted in an arid area of eastern Nevada not known to contai...

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