Using a digital relief model for searching for primary sources of gold in metamorphic complexes of the Evota region (Aldan-Stanovoy shield, North-Asian craton)

Placers of precious metals and other mineral resources are associated with the uplifted basement of the North-Asian craton and metamorphic terrains near its borders. The complex geological structure of these territories does not allow to make obvious conclusions about the sources of the placers. One of the areas of the southern outcrop of the craton basement, the Evota gold-bearing region of the Aldan-Stanovoy shield was studied. Analysis of the morphology of native gold selected from creeks of the region and eluvium from one of the primary deposits show that grains with similar morphological features occur. Probably, not far from the points of sampling, primary sources are located. Possible erosion and sediment removal should occur in positive forms of relief. Therefore, an attempt to determine the location of primary sources by modeling positive forms of relief, where erosion occurs and removal could be manifested, was made. The methodology for modeling these forms using modern geoinformation systems was considered as an attempt to analyze the obtained results. Digitized relief maps (topographic base) of the area and sample points with discovered gold were a basis for the calculations. Further steps were: building a surface of relief as a regular network of highs, calculating directions and slope angle of the surface, building a map of removal vectors, constructing a path with a maximum slope upward from the point with gold particles discover. Lines of positive forms of relief confined to gold discover points were constructed as a result. Field works for identifying signs of gold content in these lines and point sampling of rock debris were carried out. Microprobe analyses of rock debris were performed. Minerals of gold and silver were discovered in the debris. The obtained data shows that this method of analysis can be useful for deciphering ore-bearing structures and searching for primary sources.