Transcript Reynolds Partition coefficient

SERC Workshop 2010
Teaching Geochemistry
Valerie Reynolds
Colby College

Students learn how distribution
coefficients are calculated, the conditions
that influence partitioning behavior, and
how to apply this knowledge when
reading primary literature.
 Junior-level
undergraduate elective
 Mineralogy prerequisite
• Chemistry is a prerequisite for Mineralogy
 May
have had Petrology
 Assignment
is stand-alone exercise w/out
discussion
 Can be manipulated to suit different
manuscript/chemical composition (e.g.,
granite rather than basalt)

Students learn how to read scientific
literature with a critical mindset so they
can evaluate the merit of the
interpretation presented in the paper.
Husch (1990)
 Part
I: Cationic Substitution
• Mineralogy review
 Part
II: The Distribution Coefficient
• Explore Kd via GERM
 Part
III: Application of Knowledge
• Read manuscript that uses chemistry to interpret
crystallization sequence
Students refresh Mineralogy concepts

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Factors influencing cationic substitution
Coordination #’s of elements in Earth’s crust
Predict elemental substitutions
Basalt, specifically
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Given: Ni common trace element in basalt
Review basalt mineralogy and element CN’s
Predict for what/in what Ni substitutes
Geochemical Earth Reference Model
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GERM: (http://earthref.org/GERM/)
Provide specific instructions (Ni/olivine/basalt)
•
Range of Kds
•
How determined?
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Links to references
•
Calculate Kd using mineral/matrix data
•
Compare with predicted results from Part I
 Use Georef to look up article
• Husch J.M. (1990) Palisades sill: Origin of the olivine
zone by separate magmatic injection rather than
gravity settling. Geology 18, 699-702.
 Discussion of pyroxene vs olivine accumulation
 Ni, Cr, and Sc
 Timing of plagioclase crystallization
Husch (1990)
 Summary
and Discussion
• Students assigned in groups of ~3
• Groups meet to discuss paper/answer questions
• Individuals write summaries
• Class Discussion
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Exercise led well into article material
Guide questions appropriate
Article at appropriate level
Discussion particularly helpful
Subsequent assignments have students
develop the guide questions