Publication details
Modeling phase equilibria for mineral assemblages of multiphase solid inclusions enclosed in peridotite garnet
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| Year of publication | 2022 |
| Type | Conference abstract |
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| Description | Garnet peridotites of the Saxothuringian basement in the NW Bohemian Massif underwent UHP metamorphism (~4 GPa/1000°C) due to a deep subduction (Medaris et al., 2015). The multiphase solid inclusions (MSI) concentrated in the outer rim of garnet from peridotites document a widespread cryptic metasomatism by a residual carbonate-silicate liquid after UHP crystallization of garnet pyroxenite (Kotková et al., 2021). Forward thermodynamic models indicate that the phases comprising the MSI represent equilibrium. Among all the studied samples (harzburgites and lherzolites from different depths of a deep T7 borehole), the MSI in harzburgite 322 provide the most specific constraints (Fig. 1): the assemblage Dol+Cpx+Opx+Mgs+Grt+Spl+Phl is stable at relatively narrow pressure range of c. 1.8–2.1 GPa, and at high X(CO 2 )?0.7 only (calculated at a representative sectioning T=1000 °C, which is close to values obtained from conventional thermometry applied on Grt – Cpx/Opx pairs). The modeled modes of the involved phases agree well with the observed amounts. Amphibole-bearing assemblages provide less specific pressure estimates due to a strong interdependence with X(CO 2 ) of the liquid phase. Comparable pressure estimates to those above are obtained for X(CO 2 ) values close to 1. Obviously, the equilibration – (re)crystallization took place during exhumation of the hosts. |