Inclusions in Minerals

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9725566 Zhang Because the host mineral protects the inclusion, inclusions may preserve information about the deeper upper mantle, about crustal rocks subducted into the upper mantle, and the environment in the inclusion may be different from that outside. Deciphering this information requires understanding of the mechanics, thermodynamics, and kinetics of processes involving the inclusion and host. This is a combined theoretical and laboratory project to investigate the ability of the host to protect the inclusion. At (1200(C for normal mantle minerals, stress relaxation is rapid and the host can not protect the inclusion. Regular thermobarometry is applicable. At (800(C, most metamorphic rocks including some UHP's stress relaxation due to viscous flow is negligible over the age of the earth. The host can protect the inclusions. The inclusion P can be very different than the host P. Quantitative thermobarometry is possible only after inclusion-host equilibrium is understood under such conditions. Due to differences in host and inclusion P, there is a stress field in the host adjacent to the inclusion. This field may have an effect on equilibrium and may also induce pressure diffusion. Demonstrating the presence of pressure diffusion may open an new field of study and may lead to better understanding of compositional profiles in the host and applicability of such profiles in geospeedometry. Preliminary work suggests that early thermobarometry may be wrong. The results of this research will correctly interpret inclusion-host information and understand the applicability of geothermometry, geobarometry, and geospeedometry.