Podcast
Questions and Answers
What are trace elements?
What are trace elements?
Trace elements are generally impurities within the mineral structure and are distributed in consistent proportions in all phases.
Which of the following elements are considered transition metals?
Which of the following elements are considered transition metals?
- Ti (correct)
- Rb
- U
- Sc (correct)
According to Goldschmidt’s rules, what happens when two ions have the same valence and radius?
According to Goldschmidt’s rules, what happens when two ions have the same valence and radius?
They should exchange easily and enter a solid solution in amounts equal to their overall proportions.
If two ions have a similar radius but different valence, the ion with the ______ charge is preferentially incorporated into the solid over the liquid.
If two ions have a similar radius but different valence, the ion with the ______ charge is preferentially incorporated into the solid over the liquid.
Is Rb considered an incompatible element or a compatible element?
Is Rb considered an incompatible element or a compatible element?
What is chemical fractionation?
What is chemical fractionation?
What are High Field Strength Elements (HFSE)?
What are High Field Strength Elements (HFSE)?
Which trace element from Table 9-1 has the highest concentration in the solid phase according to the partition coefficients?
Which trace element from Table 9-1 has the highest concentration in the solid phase according to the partition coefficients?
Flashcards
Trace Elements
Trace Elements
Impurities within mineral structures, present in consistent proportions across all phases.
Goldschmidt's Rules
Goldschmidt's Rules
Ions with similar valence and radius exchange easily, entering solid solutions proportionally to their overall abundances.
Chemical Fractionation
Chemical Fractionation
The exchange equilibrium of a component between solid and liquid phases.
Distribution Constant (KD)
Distribution Constant (KD)
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Partition Coefficient (D)
Partition Coefficient (D)
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Incompatible Elements
Incompatible Elements
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Compatible Elements
Compatible Elements
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High Field Strength Elements (HFSE)
High Field Strength Elements (HFSE)
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Study Notes
Trace Elements
- Trace elements are impurities within mineral structures, with consistent proportions across all phases.
- Trace elements include transition metals, lanthanides, and other elements like Rb, Sr, Y, Zr, Nb, Cs, Ba, Hf, Ta, Pb, Th, and U.
- Trace elements are significantly less abundant than major elements.
- Trace element data can be used to deduce the origin and evolution of igneous and metamorphic rocks.
Element Distribution
- Goldschmidt's Rules:
- Ions with similar valence and radius exchange easily, entering solid solutions in proportions equal to their overall abundances.
- Trace elements follow the behavior of major elements.
- If 2 ions have similar radii and valence, the smaller ion preferentially enters the solid phase over the melt.
- If 2 ions have similar radii but different valence, the ion with the higher charge preferentially enters the solid phase over the melt.
- Ions with similar valence and radius exchange easily, entering solid solutions in proportions equal to their overall abundances.
Chemical Fractionation
- Chemical fractionation describes the exchange equilibrium of a component between two phases (solid and liquid).
- Distribution Constant (KD): Represents the ratio of a component's concentration in the solid phase to its concentration in the liquid phase.
- Kd = Xi(solid) / Xi(liquid)
- Xi = mol fraction of component i in the solid or liquid phase.
- Partition Coefficient (D): A special case of the distribution constant for trace elements, where concentration is in ppm or wt%.
- D = CS / CL
- CS = Concentration of trace element in solid phase (ppm or wt%).
- CL = Concentration of trace element in liquid phase (ppm or wt%).
- Incompatible Elements: D « 1, concentrated in the melt
- Example: Rb
- Compatible Elements: D » 1, concentrated in the solid phase.
- Examples: Ni, Cr, Ba
- High Field Strength Elements (HFSE):
- Smaller, highly charged trace elements
- Examples: REE, Th, U, Ce, Pb4+, Zr, Hf, Ti, Nb, Ta
- Low Field Strength Large Ion Lithophile Elements (LILE):
- More mobile than HFSE, especially in the presence of fluid phases.
- Examples: K, Rb, Cs, Ba, Pb2+, Sr, Eu2+
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