LOCAL VARIABILITY OF GOLD IN ACTIVE STREAM SEDIMENTS

The distribution of gold in a short 120 m reach of an upland stream in Scotland has been investigated using an established freeze-core sampl ing method that avoids problems of elutriation. Thirty cores were take n from six sites chosen to represent the variety of geomorphological s ettings. Bed sediments varied between sites (24.3 > D-50 > 9.2 mm). Go ld distribution is described in terms of concentration, mass and numbe r of grains. Data are erratic in coarse fractions (> 500 mu m) because of the low number of individual gold grains and the high frequency of barren samples. The < 63 mu m fraction gave the most consistent resul ts, especially for gold loads (g . kg(-1)) reflecting the high number of individual grains. The distribution of gold is discussed in relatio n to the geomorphological controls and sediment transport processes th at lead to enrichment and dilution of gold deposits. The sampling meth od is shown to provide a practical approach for obtaining representati ve and quantitative data on fine-grained gold distributions.