Geophysical properties of zinc-bearing deposits

At present, most, if not oil zinc is being produced from the mineral sphale rite. With the exception of its piezoelectricity and in some cases its dens ity, sphalerite has no salient physical properties to routinely allow its d irect detection by geophysical methods. Although the mineral usually occurs with other sulfides, which do respond to various geophysical techniques, d etection of zinc-bearing deposits is often difficult. In this paper, physic al property measurements from numerous, mainly Australian, deposits are pre sented, together with examples from various geophysical surveys. The result s ore used to suggest the most effective geophysical technique for the dire ct detection of the different types of zinc-bearing deposits. Induced polar isation is probably the most effective technique for unmetamorphosed sedime nt-hosted deposits and for carbonate-hosted deposits, whereas electromagnet ics is usually the most appropriate method to use for volcanic-hosted depos its and for sediment-hosted deposits that Rave been strongly metamorphosed. Magnetics is the best technique for skarn and 'Cobar-style' deposits. Howe ver, it must be emphasised that usually more than one geophysical technique is required before a prospect can be considered to have been thoroughly ex plored.