Retrieving "Hydrothermal Veins" from the archives

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1. Earths Crust

   Linked via "hydrothermal veins"

   The crust serves as the primary reservoir for most economically important materials. Concentration factors for these elements depend heavily on the geological history of the specific region.
   Gold ($\text{Au}$), for example, exists in the crust at an average concentration of $0.004$ parts per million ($\text{ppm}$) [8]. While this concentration is low, geological processes have co…