Subsolidus orthopyroxene-clinopyroxene systematics in the system CaO-MgO-SiO2to 60 kb: a re-evaluation of the regular solution model
✍ Scribed by Klaus G. Nickel; Gerhard Brey
- Publisher
- Springer
- Year
- 1984
- Tongue
- English
- Weight
- 890 KB
- Volume
- 87
- Category
- Article
- ISSN
- 0010-7999
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✦ Synopsis
On the basis of an increased set of experimental data, covering the miscibility gap between orthopyroxene and clinopyroxene from 2 to 60 kb with a temperature range of 850-1,500 ~ C, we present a new version of a regular solution model. The model with two independent regular solutions for opx and cpx is capable of reproducing experimental data in the system CaO-MgO-SiO 2 over a large range of temperatures and pressures. It is qualitatively in agreement with observed stability regions for an Fe-free low-Ca pyroxene, termed pigeonite. The model is constrained by and thus consistent with calorimetric measurements on pyroxenes. The simple form of equations provides a good starting point for the development of more reliable thermometers based on the miscibility gap.