In magmatic systems, ores and host rocks are derived from the same fluid. In the case of hydrothermal fluids, host rocks are older than the predominantly aqueous fluids that carry and deposit metals and thus complicate defining a host rock associated with gold fluid formation. A number of rock types have been suggested as the source of orogenic gold, but due to the variability of host rocks in Earth’s history and deposit-scale, their relation to Earth-scale gold formation processes is unclear. Furthermore, age dating of the deposits and their host rocks shows that there are large time gaps in their formation. Age dating indicates that mineralization took place 10 to 100 Ma after the formation of the host rocks. These temporal gaps suggest an overall genetic independence of the fluid formation and that of local lithologies.
