Blind and buried mineral deposits in wet climates

Four case studies in areas of high rainfall were carried out in the CSIRO project. In Tasmania, three small stratiform massive sulphide occurrences covered by fluvioglacial 

At the Henty Fault Zone the Hg contents of fresh sulphides are relatively low, averaging about 600 ppb. Soil was sampled from both the A and B/C horizons, with Hg being concentrated in the A horizon (Fig. 12-24). Possibly-anomalous levels of Hg in the A horizon are coincident with Zn and Cu anomalies, which strongly suggests a mechanism of enrichment other than vapour transport. Also, analysis of samples from overburden profiles (fluvioglacial deposits and overlying soils) above the sulphide lens do not indicate the formation of vapour-generated Hg halos (Fig. 12-25). 

Similar patterns are associated with sulphide veining in a road-cutting near the Bastyan dam. Mineralisation is restricted to several narrow sphalerite-rich veins over a stratigraphic interval of about 0.5 m. High levels of Hg (10,000 ppb) associated with the veining are not reflected in the overlying tills and soils (Figs. 12-26 and 12-27). 

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