GYDROTHERMAL ALTERATION AND ORE DEPOSITION IN SERPENTINITE-TYPE MERCURY DEPOSITS

Mercury sulfide deposits are classified according to the host rock in which they were deposited. The petrology, wallrock alteration, and ore mineralization of the Mt. Jackson mine, California, are summarized and are considered typical of the serpentinite-type mercury sulfide deposits and probably genetically similar to mercury sulfide deposits occurring in other host rock types. Using the Mt. Jackson mine as a representative example of serpentinite-type mercury sulfide deposits, it is shown that the reaction: serpentinite + associated thermal springs solution will produce the silica-carbonate rock, gangue, and ore minerals in the proportions observed. The thermal springs solution is shown to be a partially spent ore solution. The dominant chemical control of the mercury sulfide deposition in such an environment is the contemporaneous reaction between the thermal springs ore solution and the serpentinite host rock. Thus, in any $erpentinite-type mercury sulfide province, the presence of silica-carbonate rock should initially be considered a strong indicator of potential mercury ore. © 1969 Society of Economic Geologists, Inc.