Preglacial to Holocene auriferous sediments from the East Sudetic Foreland: gold grades and exploration

摘要

Auriferous sediments in the East Sudetic Foreland region include up to five gold-bearing horizons associated with preglacial and Quaternary fluvial sediments. The largest placer potential lies in the preglacial (Eopleistocene?) drainage system, primarily in palaeochannels of the Biala Gluchotaska River. The White Gravel series is the richest gold-bearing horizon. It contains between 0.37 g/m~3 Au near the base and <0.10 g/m~3 Au in its upper part. Maximum gold grade occurs in the first 1-2 m above the contact with the bedrock. Gold concentration in this area was controlled by the ability of streams to aggradation and the development of sedimentologic traps, where gold was accumulated during the preglacial valley erosion. Oblique orientation of the palaeo-Biala Glucholaska valley and its tributaries to the regional ice-flow direction probably prevented the glaciers from eroding deeply into the palaeochannels. From the exploration prospective, study of palaeochannel systems in the vicinity of Otmuchow-Prudnik could identify other buried placer gold occurrences. Gold-bearing sediments, correlated stratigraphically with the Biala Glucholaska palaeochannel White Gravels occur in several other areas, including the Nysa Klodzka, Kwisa and Kaczawa valleys.