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The pressure path of solid inclusions in minerals: the retention of coesite inclusions during uplift |
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| Authors: | I Van der Molen HLM Van Roermund |
| Institution: | Department of Structural Geology, Institute of Earth Sciences, University of Utrecht, 3508 TA, Utrecht, The Netherlands |
| Abstract: | An inclusion model allows calculation of the stresses in and around minerals included in other minerals: during changes in pressure and temperature. The equations are applied to illustrate cooling and uplift histories of quarzo-feldspathic rocks from 500°C and various pressures to ambient conditions. Even in the absence of pore-fluid pressure, microfractures may open at external pressures of 200–400 MPa and temperatures of 200–400°C due to differential volume changes of the constituent minerals. Coesite included in garnet cannot have formed during progressive metamorphism from quartz at lithostatic pressures below the coesite stability field because of differential volume changes. Coesite inclusions are captured by their host minerals at ultra-high pressures and they persist to lower pressures because of the large volume increase occurring at the coesite to  -quartz transition. The Pi-T path followed by the SiO2 inclusion traces the boundary between the stability fields of coesite and -quartz until radial fractures develop in the host at low external pressure. |
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