| Session Description |
Mineral deposits form where new minerals are precipitated from magmas or fluids in response to changes in tectonic processes and of mineral-forming conditions in pressure, temperature, and chemical environment. Mineral deposits occur in a variety of geological environments in the Earth's crust. Mineral deposits of an individual element need not to be restricted to a single geological and tectonic setting. Elemental associations may, however, be indicative of a specific orogenic and paleotectonic setting because of differing geochemical processes leading to mineral enrichment. The formation of certain mineral deposit types can be ascribed to processes that are mainly magmatic, that is, to processes related to the cooling and solidification of magmas and the chemical composition of the magma from which they formed. Fractional crystallization is usually important in plutonic rocks, whereas post-magmatic hydrothermal circulation is significant in all geological environments from plutonic, volcanic and sedimentary to metamorphic conditions. Crystallization of oxides during early magma genesis can generate chromium-, iron-, vanadium-, or titanium-rich layers of economic importance and may relate to formation of gemstones. Post-magmatic hydrothermal processes can generate base and precious metal-rich deposits of porphyry, skarn, mesothermal to epithermal types. Volcanic-hosted massive sulphide (VHMS) deposits and sedimentary exhalative (SEDEX) deposits are composed predominantly of iron sulphides (pyrite, pyrrhotite), and economic amounts of copper, zinc, and lead sulphides. Economically important contents of gold and silver are also present in most orebodies. These sulphide ores are related to hydrothermal fluid circulation in submarine environments. The Asia and Pacific region, in particular, has many diverse metallogenic provinces of different mineralization styles and mineral commodities, such as zinc, lead, copper, gold, silver, tin, tungsten, molybdenum, bismuth, antimony, uranium, and rare earth elements and gem deposits. The gem deposits are also highly significant in terms of monetary value, with annual worldwide production exceeding several billion dollars. However, accurate production figures are extremely difficult to come by, as many of these deposits are worked by individuals or small groups of miners. The understanding their genesis is also limited, although they are of especial economic significance in a number of developing economies in Asia and Africa where they account for a significant proportion of the gross domestic product, both in terms of mined rough and manufactured products. This session will focus upon the orogenesis, magma genesis and mineral genesis with special emphasis on gemstones and sulphide ores and welcome any contribution relating to review of previous studies as well as new data and new interpretation on this subject.
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