Time Estimates for Oxygen Isotopic Exchange During Mineral-Fluid Interaction in Hydrothermal Systems

Abstract

Oxygen isotopic shifts observed in hydrothermal ore deposits and geothermal systems have resulted from surface exchange reactions during rock water interaction at elevated temperatures. Duration required to produce the observed isotopic shifts in these system can be modeled from a modified surface exchange rate equation for a sphere. We have assumed that the solid fluid interactions occurred under conditions of constant temperature and grain size and the fluid flow rates were slow relative to isotopic exchanges rates, such that the systems appear static. Times required to produce the isotopic shifts observed in hydrothermal systems are typically less than 200 years. Because the total duration of activity is probably on the order of 10/4-10/6 years, the time estimated by the surface exchange model may represent only a single episode in the lifetime of the system.