Surface-related formation, upgrading, and improvement of ore deposits A review of supergene metallogenic processes

摘要

Supergene metallogenic processes occur on two different scales and include both ⅰ) oxidation and upgrading of pre-existing ore bodies at some depth and ⅱ) the formation of ore deposits by weathering processes at or immediately below the surface. The former group comprises deposit types such as enrichment blankets of porphyry copper, non-sulphide zinc deposits, uranium roll fronts, and banded manganese/iron formations. The latter group is made up of bauxite, nickel- and iron-laterite, chromium, titanium and locally platinum group element (PGE) and rare earth element (REE) deposits. The understanding of the supergene ore forming processes depends on the recognition and reconstruction of a wide range of surface-related processes. These include, besides the more classical disciplines such as ore-chemistry and ―mineralogy, particularly the erosional history, palaeo-climatology, and ―hydrology of the deposits. Numerous supergene deposits with either exotic mineralogy or very low metal contents have become economically viable due to new ben-eficiation techniques, i.e. hydro- instead of pyrometallurgy. The lower recovery costs will result in enhanced exploration efforts for low-grade, near-surface, bulk-minable, and environmentally improved ore deposits of both base and precious metals, probably with an increasing percentage of supergene deposits.