Textural evolution of polyhedral olivine experiencing rapid cooling rates

• Published in: Contributions to mineralogy and petrology Vol. 153; no. 4; pp. 405 - 416
• Main Authors: Faure, François, Schiano, Pierre, Trolliard, Gilles, Nicollet, Christian, Soulestin, Bernard
• Format: Journal Article
• Language: English
• Published: Heidelberg Springer Nature B.V 01.04.2007
• Subjects: Crystallization; Experiments; Geology; Integrated approach; Microscopy; Mineralogy; Petrology
• ISSN: 0010-7999; 1432-0967
• DOI: 10.1007/s00410-006-0154-8

Dynamic crystallization experiments in the CaO-MgO-Al2O3-SiO2 (CMAS) system have been used to investigate the change in crystal shape when pre-existing polyhedral olivine crystals are cooled rapidly (1,639-2,182 degrees C/h). Polyhedral olivines are crystallized initially in a first step using a slow cooling rate (2 degrees C/h), then skeletal and dendritic overgrowths develop on the polyhedral crystals during a subsequent fast cooling event. During this second episode small dendritic olivines also nucleate within the liquid phase. Observation of the experimental sample by optical microscopy shows that the polyhedral olivine shape progressively changes to a skeletal and then to a dendritic morphology in the following sequence: polyhedral [implies] hopper polyhedral [implies] dendritic polyhedral. This evolutional sequence is discussed in terms of changes in the crystal growth conditions during cooling and a general relation between these olivine dynamic crystallization experiments and the integrated model of crystal growth by Sunagawa (Bull Miner 104:81-87, 1981, Morphology of crystals, Terra Scientific Publishing Company, 1987) is proposed. [PUBLICATION ABSTRACT]