Preliminary examinations of the ore-forming process by fluid mixing - a test of MIX99

Possible ore deposition by fluid mixing was preliminarily examined using MI X 99, a FORTRAN program developed for simulating water-rock interactions. W e consider mixing of two fluids, the low f(O2) and high temperature source fluid and the high f(O2) and low temperature seawater. Oxygen fugacity of a mixed fluid formed by titration of seawater into the source fluid graduall y decreases with decreasing temperature (model A). Sequential precipitation of ore-forming minerals was examined in this model. On the other hand, sim ultaneous precipitation of the minerals could be followed by simulation of instantaneous overall mixing of the two fluids (model B). Results of simula tion of the both models revealed that a temporal sequence of mineralization observed in the Karuizawa mine, NE Japan, can be formed by model A, while model B is suitable for the mineralization of an active chimney found in th e Rainbow hydrothermal area of the Mid-Atlantic Ridge.