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1. 1 Binary Phase Diagrams GLY 4200
2. 2 Binary Diagrams Binary diagrams have two components
We therefore usually choose to plot both T (temperature) and X (composition) with pressure held constant
P-X (T fixed) or P-T (X fixed) are also possible
3. 3 Binary System Examples Binary solid solution - olivine, plagioclase feldspar
Binary eutectic with congruent melting - potassium feldspar - silica
Binary peritectic and eutectic with solid to solid conversion - leucite - Potassium feldspar - silica
Binary minimum melting point - potassium feldspar - albite
Binary minimum melting point with solvus - potassium feldspar - albite
4. 4 Phase Rule for Binary Systems f = c - p + 2 = 2 - p + 2 = 4 - p
If two phases are present, there are two degrees of freedom (both T and X)
If three phases are present, there is one degree of freedom (either T or X)
5. 5 Binary Solid Solution Plagioclase Feldspar series, 39% of the earth?s crust
6. 6 Phase Rule Application How many degrees of freedom are present at points 1,2, and 3?
7. 7 Binary Eutectic Diagram Conventions Two immiscible components: such as CaAl2Si2O8 (calcic plagioclase) and FeMgSiO4 (olivine) plotted along the horizontal axis, OR olivine (isolated tetrahedra) and pyroxene (single chain tetrahedra), which are immiscible because they have different crystal structures
One variable, temperature, plotted along the vertical axis.
Pressure is held constant at 1 atmosphere.
Three phases, crystal A, crystal B, and melt.
Complete miscibility of the melt (magma)
8. 8 Binary Eutectic Diagram Assumptions The system remains in equilibrium throughout its history, so that all reactions can take place and everything can come to stability
Everything in the original melt remains in communication throughout the crystallization process
9. 9 Binary Eutectic Diagram Source: http://csmres.jmu.edu/geollab/Fichter/IgnRx/BinryEu.html#GiveitatrySource: http://csmres.jmu.edu/geollab/Fichter/IgnRx/BinryEu.html#Giveitatry
10. 10 Binary Eutectic Diagram ? Intermediate Compositions Source: http://csmres.jmu.edu/geollab/Fichter/IgnRx/BinryEu.html#Giveitatry
11. 11 Binary Eutectic Crystallization Source: http://csmres.jmu.edu/geollab/Fichter/IgnRx/BinryEu.html#GiveitatrySource: http://csmres.jmu.edu/geollab/Fichter/IgnRx/BinryEu.html#Giveitatry
12. 12 Binary Eutectic Melting Source: http://csmres.jmu.edu/geollab/Fichter/IgnRx/BinryEu.html#Giveitatry
13. 13 Melting A Rock With A 30/70 Eutectic Source: http://csmres.jmu.edu/geollab/Fichter/IgnRx/BinryEu.html#Giveitatry
14. 14 Fractionation Source: http://csmres.jmu.edu/geollab/Fichter/IgnRx/BinryEu.html#Giveitatry
15. 15 Congruent Melting The previous case is an example of congruent melting
Congruent melting means melting of a substance directly to a liquid that is of the same composition as the solid
16. 16 Incongruent Melting Melting accompanied by decomposition or by reaction with the liquid, so that one solid phase is converted into another
Melting to give a liquid different in composition from the original solid
One example occurs in the forsterite-quartz system
17. 17 Binary Eutectic with Incongruent Melting L = Liquid
Fo is fosterite
En is enstatite
Qtz is quartz Diagram: fo-qtz6.gifDiagram: fo-qtz6.gif
18. 18 Reaction MgSiO3 + SiO2 = Mg2SiO4
En + Qtz = Fo
19. 19 Fo- Qtz
20. 20 Forsterite ? Quartz at Higher T Two liquid phases are present on the right side of the diagram Diagram: fo-qtz.gifDiagram: fo-qtz.gif
21. 21 Binary Minimum Melting Point Diagram: phase21.gif from http://www.uh.edu/~jbutler/petrography/phase21.gifDiagram: phase21.gif from http://www.uh.edu/~jbutler/petrography/phase21.gif
22. 22 Albite - Orthoclase Diagram: phdifig4.gifDiagram: phdifig4.gif
23. 23 Lever Adapted from: http://www.msm.cam.ac.uk/doitpoms/tlplib/CD4/images/diagram31.gifAdapted from: http://www.msm.cam.ac.uk/doitpoms/tlplib/CD4/images/diagram31.gif
24. 24 Application of Lever Rule C = 65 weight% ? Adapted from: http://www.msm.cam.ac.uk/doitpoms/tlplib/CD4/images/diagram32.gifAdapted from: http://www.msm.cam.ac.uk/doitpoms/tlplib/CD4/images/diagram32.gif
25. 25 Point 2 Solid phase B starts to form with a composition of 96 weight% ? Source: http://www.msm.cam.ac.uk/doitpoms/tlplib/CD4/images/diagram33.gifSource: http://www.msm.cam.ac.uk/doitpoms/tlplib/CD4/images/diagram33.gif
26. 26 Point 3 C1 = 58 weight% ? and C2 = 92 weight% ?
Source: http://www.msm.cam.ac.uk/doitpoms/tlplib/CD4/images/diagram34.gifSource: http://www.msm.cam.ac.uk/doitpoms/tlplib/CD4/images/diagram34.gif
27. 27 Point 3 Calculations Fraction of solid b = (65 - 58) / (92 - 58) = 20 weight%
Fraction of liquid = (92 - 65) / (92 - 58) = 80 weight%
28. 28 Point 4 C3 = 48 weight% ?
C4 = 87 weight% ?
Source: http://www.msm.cam.ac.uk/doitpoms/tlplib/CD4/images/diagram35.gifSource: http://www.msm.cam.ac.uk/doitpoms/tlplib/CD4/images/diagram35.gif
29. 29 Point 4 Calculations Fraction of solid with composition C4 = (65 - 48) / (87 - 48) = 44 weight%.
Fraction of liquid at eutectic = 56 weight%
30. 30 Point 5 C5 = 9 weight% ? and C6 = 91 weight% ?
Source: http://www.msm.cam.ac.uk/doitpoms/tlplib/CD4/images/diagram36.gifSource: http://www.msm.cam.ac.uk/doitpoms/tlplib/CD4/images/diagram36.gif
31. 31 Point 5 Calculations Fraction of solid with composition C6 = (65 - 9) / (91 - 9) = 68 weight%
Fraction of solid with composition C5 = (91 - 65) / (91 - 9) = 32 weight%
32. 32 Effects of Pressure With increased pressure, from 1 atm to 7 kbar, En changes from incongruent to congruent melting behavior
The field of liquid immiscibility, the 2L field on the 1 atm diagram, disappears at slightly elevated pressures and is no longer evident in the 3 kbar diagram. Source: http://www.brocku.ca/earthsciences/people/gfinn/petrology/binary9.htmSource: http://www.brocku.ca/earthsciences/people/gfinn/petrology/binary9.htm
33. 33 Orthoclase ? Albite at Low P Source: http://www.brocku.ca/earthsciences/people/gfinn/petrology/ab-or1.gifSource: http://www.brocku.ca/earthsciences/people/gfinn/petrology/ab-or1.gif
34. 34 Orthoclase ? Albite at 5 kbars Source: http://www.brocku.ca/earthsciences/people/gfinn/petrology/ab-or2.gifSource: http://www.brocku.ca/earthsciences/people/gfinn/petrology/ab-or2.gif
35. 35 Reading a Ternary Diagram Image: tri.gifImage: tri.gif
36. 36 Points on Diagram Edge Points on the edge have only two components Image: tri2.gif
37. 37 Reading Sample Points Note that the scales are plotted increasing in a CCW directions Image: ternread-d.gifImage: ternread-d.gif
38. 38 Ternary Rock Composition Diagram Ternary diagrams can be used to plot any three things Image: ternread-f.gif
39. 39 Texture Diagram Another use of ternary diagrams Image: textsand.gifImage: textsand.gif
40. 40 Ternary System Sample ternary diagram
42. 42 Real Plot Image: System_Na_K_AL_Si_O.gifImage: System_Na_K_AL_Si_O.gif