A mercury vapor survey in an area of thick transported overburden near Shanghai, China

Experimental surveys of Hg vapor in alluvium cover (up to 180 m thick) over a skarn copper deposit in the vicinity of Shanghai have shown encouraging results. Abundance and zoning of Cu, Pb, Zn, Ag, Mo, Mn, Sn, W, Ba, Bi, Co and Cl in soils and drill cores were studied for comparison.A distinct soil-gas Hg anomaly was discovered over the deposit. Repeated surveys carried out in different seasons during 1978 and 1979 show little variation in shape, dimension and intensity of the Hg anomalies.High soil-gas Hg values appear to be closely related to contacts, faults and fracture zones.Element zoning is well defined by the dispersion of Hg, Cu, Ag, etc. The zoning index of Hg and other elements shows that Hg is a typical front element.Thermo-release curves of Hg obtained by heating rock, ore and alluvium samples indicate that Hg has three forms of occurrence: easily volatilized Hg, chloride Hg, and sulphide Hg. Mercury chloride and volatile Hg represent the predominant phase in alluvium samples.