HR: 09:30h
AN: V11A-07    [PDF]
TI: Monitoring and Quantifying Texture Evolution During Experimental Crystallization and Melting Using Crystal Size Distributions
AU: * Zieg, M J
EM: michael.zieg@sru.edu
AF: Department of Geography, Geology, and the Environment, Slippery Rock University 1 Morrow Way, Slippery Rock, PA 16057 United States
AU: * Zieg, M J
EM: michael.zieg@sru.edu
AF: NASA Johnson Space Center, Mail Code ST 2101 NASA Road 1, Houston, TX 77058 United States
AB: A study designed to relate crystal size distributions (CSDs) quantitatively to specific magmatic conditions has been conducted using a series of high temperature heating and cooling experiments with defined initial crystal populations and controlled thermal trajectories. These experiments provide a method for empirically exploring the development of textures under particular conditions and for testing models of crystallization kinetics. Textural evolution during melting was examined by heating a mixture of olivine crystals and synthetic glass at three different temperatures (1545, 1500, 1450 $\deg$C) for durations ranging from 0 to 60 min before quenching. CSDs were measured for each sample, and the texture evolution was quantified in terms of the population density as a function of experimental duration. Initially, the population density for the smallest size classes sharply decreased as these crystals melted. With increasing duration, the maximum grain size and the population density in the larger size classes increased. This may have been due to coalescence or crystal growth. Textural evolution during cooling was determined by melting an olivine + glass mixture at 1545 $\deg$C for 5 min, and then cooling along a 100 $\deg$C/hr gradient. Samples were quenched at different points along the crystallization trajectory. This series of samples serves as a monitor for the texture evolution during a 100 $\deg$C/hr cooling run. The CSDs show minor changes in the smaller size classes and major increases in population density in the larger size classes. These changes are interpreted to be the result of ongoing nucleation and rapid growth of skeletal olivine crystals at the top of the charge. The results of these experiments can be used to estimate the olivine growth rate under conditions similar to those experienced by porphyritic olivine chondrules.
DE: 3630 Experimental mineralogy and petrology
SC: Volcanology, Geochemistry, Petrology [V]
MN: 2003 Fall Meeting