Ore-bearing Granite Systems; Petrogenesis and Mineralizing Processes

Magmatic and hydrothermal processes in ore-bearing systems
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Published:January 01, 1990
The alphabet soup of granite types and its association with certain ore deposit types is called into question. We now realize that granites do not retain a menu of ingredients inherited at the site of their generation, and that initial magma chemistry is only one of several influences on the potential for later ore formation in granite systems. Rather, processes leading to fluid release and crystal-melt and fluid-melt fractionation of critical elements, mainly metal species and volatile complexing agents, are central to the formation of ore. These processes are certainly influenced by tectonic setting, source mineralogy and chemistry, assimilation, contamination, and geothermal gradient, but are not strictly controlled by them. The delicate relations between a granite magma, its crystallizing phases, volatile content and species, and oxygen fugacity, plus the timing and mechanism of fluid release and the efficiency of metal extraction, ultimately control the formation of an ore deposit.
As experimental data become more available, models for granite-related ore deposits must incorporate and emphasize the important role of crystal and volatile fractionation in the system. In other words, we need to model the process as well as the source.
- A-type granites
- assimilation
- complexing
- crystal fractionation
- crystallization
- differentiation
- genesis
- geochemistry
- geothermal gradient
- granites
- I-type granites
- igneous rocks
- magma contamination
- magmas
- mechanism
- metal ores
- partitioning
- phase equilibria
- plutonic rocks
- processes
- S-type granites
- volatiles
- M-type granites