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Week 6: Feb. 14 - Feb. 18
Phase diagrams (cont'd)
-
3 component system without
solid solution and a simple eutectic (Di-An-Fo) - continued
-
equilibrium crystallization
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fractional crystallization
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equilibrium melting
-
fractional melting
-
determining (a) proportions
of solids to liquids, (b) total solid compositions and total liquid compositions,
(c) instantaneous solid compositions
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Melting occurs where
the three phases are in mutual contact
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Schematic Fo-Di-En diagram,
melting of lherzolite and formation of basalt and residual harzburgite.
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3 component system with
solid solution (Ab-An-Di)
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Bowen's Reactions Series
(Chapter 5 of Bowen, 1928, The Evolution of Igneous Rocks)
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Continuous Reaction
Series (e.g., Ab-An)
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Discontinuous Reaction
Series (e.g., Fo to En, pyx to hbl, hbl to bt)
-
confirmation of continuous
and discontinuous reaction series from petrographic observations (zoning
and coronas)
-
Bowen's reaction series
is a summary of commonly observed reaction relations in the "ordinary subalkaline
rocks"
-
fractional crystallization
of basaltic subalkaline magmas
-
common rock associations
possibly explained by Bowen's reaction series and fractional crystallization
-
cumulate rocks
The mantle and the
generation of basalt
-
Review gross structure
of Earth
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Present locations where
magmatism is occurring
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mid-ocean ridges
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continental rifts
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subduction zones
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hot spots
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Sources of information
about the mantle
-
seismology
-
xenoliths in alkali-rich
magmas (kimberlites and alkali basalt)
-
meteorites
-
chondrites (undifferentiated
meteorites) - primordial solar system material
-
achondrites - differentiated
meteorites
-
"irons" = planetary
core material
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"stones" = planetary
crust and mantle
-
peridotitic achondrites
(mantle)
-
basaltic achondrites
(crust)
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abyssal peridotites
- exposed primarily along transform faults and fracture zones
(to be continued ..)
Petrology
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