MESOTHERMAL VEINS:

Mesothermal gold deposits are formed from hot water that precipitates gold under high temperatures and pressure, generally at great depths in the earth's crust (around 10km). In these deposits, high gold grades tend to be continuous over large vertical ranges.

This process has formed throughout geologic history but younger examples include the Mother Lode District in California and the Bralorne-Pioneer District in B.C. Nearly 80% of B.C.'s gold production has been mined from mesothermal veins, which includes Almaden's Elk Gold Mine.