Fluid inclusions as tectonothermobarometers: Relation between pressure-temperature history and reequilibration morphology during crustal thickening

Abstract

Results of experimental reequilibration studies of natural primary aqueous inclusions in quartz under conditions of hydrostatic compressive loading at 1, 2, 3, 4, and 5 kbar and 500 °C indicate that the intensity of reequilibration features is inversely proportional to inclusion volume. The smallest inclusions show the first evidence of reequilibration (dissolution of inclusion walls) after ∼1.8 kbar of effective pressure. For effective pressures less than ∼3.8 kbar, decrepitation of inclusions is probably controlled by the corrosive action of water on the inclusion walls. At higher effective pressures, decrepitation is related to high compressive stress and is less dependent on fluid interaction with the inclusion walls. The observed correlation between inclusion size, intensity of reequilibration features, and amount of loading, combined with paragenetic and microthermometric data for the inclusions, may be used to determine the pressure-temperature history of the inclusions and their host rocks.