Revised activity–composition models for clinopyroxene and amphibole |
| |
| Authors: | J F A DIENER R POWELL |
| |
| Institution: | 1. Department of Geological Sciences, University of Cape Town, Private Bag X3, Rondebosch 7701, South Africa (johann.diener@uct.ac.za);2. School of Earth Sciences, University of Melbourne, Melbourne, Vic. 3010, Australia |
| |
| Abstract: | Recent activity–composition models for clinopyroxene and amphibole are revised to provide better consistency with observed phase relations in natural rocks. For clinopyroxene, the calibration in NCFMAS is retained, but the incorporation of acmite is revised to improve the partitioning of ferric iron between coexisting clinopyroxenes. For amphibole, the NCFMASH calibration is retained, but the addition of ferric iron is changed to provide consistency with the clinopyroxenes. The thermodynamics of orthoamphibole (gedrite) is also adjusted to resolve an unrelated inconsistency. The effects of these improvements are illustrated through comparison of calculated pseudosections produced with the existing and new models with natural data from lawsonite eclogites. |
| |
| Keywords: | amphibole clinopyroxene mineral equilibria |
|
|
