A practical classification of gold deposits, with a theoretical basis

Well-considered schemes that classify ore deposits can be effective contributors to exploration success, understanding of deposit genesis, mining geology, engineering, metallurgy, property valuations and stock market analysis. An effective classification scheme needs to be easy to apply without ambiguity and is much more powerful if based on sound scientific principles. For deposits with economic gold, a useful classification recognises gold-only and gold-plus deposits based upon whether they also have economic base metals. The scheme is easy to apply and in most cases unambiguous for specific deposits and whole provinces. The subdivision has a sound scientific basis that involves the chemistry of gold in relation to metal complexing, salinity of ore-forming fluids and redox state. Forward modelling from chemical principles can be integrated with inverse modelling from observations to add confidence in this classification and thus be used to create exploration opportunities.The Jiaodong gold province of eastern China comprises deposits mostly in granitic rocks with economic gold but low levels of base metals; the inferred ore fluids are of low to moderate salinity. From their gold-only character, several other aspects of their development can be inferred, though the tectonic and metamorphic history remains unresolved. The granitic host rocks appear to reflect a chemically and mechanically favourable site for deposition, not a source for the gold or the ore fluid neither of which have been established yet.