| Abstract: | Contamination of gold ring and natural gold grains into plastic capsules used in INAA analysis and the fine fraction of till (0.064 mm) have been studied. An artificial contamination of till samples with a gold ring caused Au contents of 100–600 ppb in the fine fraction. A few rubbings of plastic capsules with a gold ring gave Au amounts of 15–170 ng per capsule. Natural gold grains of sizes 0.1–1.0 mm added into “gold-free” till samples before drying and sieving caused Au contents of 1–27 ppb into the fine fraction. In a regional geochemical survey an anomaly of a few hundreds of square kilometers with concentrations of 100–600 ppb Au in the fine fraction of till was observed. Later studies showed that this area was very low in Au, concentrations being generally below one ppb. The anomaly was interpreted as a contamination caused by the gold rings of the samplers. |
