Groundmass crystallization of Mount St. Helens dacite, 19880-1986: a tool for interpreting shallow magmatic processes
Article Abstract:
The groundmass crystallization of Mount St. Helens' magmatic reservoir can serve as a model in the study of shallow magmatic systems. The observational results show that the rate of change in average crystal size and anorthite content lessens with time. Furthermore, the shallow intrusion and depressurization with the concurrent gradual cooling of the magma reservoir have resulted in chemical and textural changes in the silicic system. Finally, the thermal and chemical model derived from the system can be applied to develop other models of magma reservoir and eruption.
Publication Name: Contributions to Mineralogy and Petrology
Subject: Earth sciences
ISSN: 0010-7999
Year: 1992
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Experiments and models of anhydrous, basaltic olivine-plagioclase-augite saturated melts from 0.001 to 10 kbar
Article Abstract:
A model based on phase diagrams facilitates the determination of the fractional crystallization paths in olivine-plagioclase-augite basalts. Empirical equations are used as a thermobarometer to estimate the variations in temperature and composition in these rocks for different pressures. Augite composition plays an important role in the crystallization history. Detailed results of 190 anhydrous experiments are provided. Glasses from the east limb of the East Pacific Rise have been used to illustrate the workability of the proposed model.
Publication Name: Contributions to Mineralogy and Petrology
Subject: Earth sciences
ISSN: 0010-7999
Year: 1996
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Relationship between plagioclase crystallization and cooling rate in basaltic melts
Article Abstract:
An analysis of the relationship between plagioclase crystallization and cooling rates is presented. The analysis sets conditions of simple cooling and absent convection or mixing. It is shown that such conditions generate textures which define sample cooling rate, the temperature which catalyzed crystallization and the distribution of mineral phase precipitation. In addition, plagioclase logarithmic data indicate similar conditions for pyroxene and magnetite crystallization.
Publication Name: Contributions to Mineralogy and Petrology
Subject: Earth sciences
ISSN: 0010-7999
Year: 1993
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