Gold Deposits at Goldstrike, Utah

Abstract Disseminated gold deposits that aggregate more than 1 million tons have been indicated by drilling in the Goldstrike district, northwestern Washington County, Utah. Nearly all of this gold occurs in a sandstone to conglomeratic sandstone unit that is locally the basal member of a formation that we correlate with the Tertiary Claron Formation. The gold-bearing rocks have not been studied petrographically and the manner of occurrence of the gold is not known. It has not been identified visually, and it cannot be concentrated by panning. It is, however, readily soluble in a cyanide-leach assay and is assumed to be free gold. Arsenic, mercury, and minor antimony are associated with the gold. The Paleozoic rocks in the district have been complexly folded and faulted and the Tertiary Claron Formation was deposited on an irregular surface that exposed all but one of the Paleozoic formations. The Paleozoic carbonate rocks have been altered to jasperoid along high-angle faults and along the irregular contact with the Claron at most places where the basal member of the Claron is conglomeratic sandstone or sandstone. The jasperoid bodies commonly contain gold and are a fairly reliable indicator of ore in the overlying clastic unit of the Claron Formation.