Document Type
Thesis
Degree
Master of Science (MS)
Major/Program
Geosciences
First Advisor's Name
Rosemary Hickey-Vargas
First Advisor's Committee Title
Committee Chair
Second Advisor's Name
Guatam Sen
Third Advisor's Name
Andrew McFarlane
Fourth Advisor's Name
Grenville Draper
Fifth Advisor's Name
Fidel Costa Rodriguez
Date of Defense
2-16-2007
Abstract
Calbuco Volcano, in Southern Chile, has eruptive products of predominantly andesitic hornblende-bearing lava. A purpose of this work is to understand magmatic processes and how Calbuco magma chemistry is related to the explosive volcanic character. Calbuco lava has a mineral assemblage of plagioclase, hornblende, orthopyroxene, clinopyroxene, olivine, and magnetite and entrained gabbroic xenoliths with the same mineral assemblage. The presence of hornblende is evidence for dissolved water in the magma. Detailed petrographic/textural analysis has been done using petrographic microscopy and back-scattered electron imaging (BSE); geochemical analysis by electron microprobe (EPMA). Major findings include 1) that hornblende and hornblende-bearing gabbroic cumulates crystallize from Calbuco magma, 2) that plagioclase grains are compositionally zoned, recording evidence of temperature, chemical, and water content fluctuations in the magma, and 3) that hornblende is unstable under upper magma chamber conditions at Calbuco, and is breaking down into plagioclase, olivine, orthopyroxene, clinopyroxene, and magnetite in the magma.
Identifier
FI15071602
Recommended Citation
Horst, Tiffany Sperry, "Determining magmatic processes from analysis of phenocrysts and gabbroic xenoliths contained in Calbuco andesites" (2007). FIU Electronic Theses and Dissertations. 2007.
https://digitalcommons.fiu.edu/etd/2007
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