A developmental model of olivine morphology as a function of the cooling rate and the degree of undercooling |
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| Authors: | Faure François Trolliard Gilles Nicollet Christian Montel Jean-Marc |
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| Institution: | (1) Laboratoire "Magmas et Volcans", Observatoire de Physique du Globe de Clermont-Ferrand, UMR 6524 CNRS, Université Blaise Pascal, 5 rue Kessler, 63038 Clermont-Ferrand Cedex, France;(2) Science des Procédés Céramiques et de Traitements de Surface, UMR 6638 CNRS, 123 avenue Albert Thomas, 87060 Limoges Cedex, France;(3) Laboratoire des Mécanismes de Transfert en Géologie-Minéralogie, UMR 5563 CNRS, 39 allées Jules Guesde, 31000 Toulouse, France |
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| Abstract: | We performed dynamic crystallization experiments in the CMAS system at 1 atm to investigate the evolution of the morphology of forsterite crystals as a function of cooling rate and degree of undercooling. In sections parallel to the (010) plane, we observed the evolution of the forsterite morphology from tablets to hopper (skeletal) crystals, and then to swallowtail shapes (dendritic morphology) for increased degree of undercooling. The other shapes described in the literature can be interpreted as particular sections of those three shapes. The onset of dendritic growth is due to a competition between the growth of the faces of the initial hopper crystal and dendrite overgrowths. The forsterite dendrites are formed by a succession of units which look like hopper shapes. This result has been tested by an additional set of experiments. |
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