Loading presentation...

Present Remotely

Send the link below via email or IM

Copy

Present to your audience

Start remote presentation

  • Invited audience members will follow you as you navigate and present
  • People invited to a presentation do not need a Prezi account
  • This link expires 10 minutes after you close the presentation
  • A maximum of 30 users can follow your presentation
  • Learn more about this feature in our knowledge base article

Do you really want to delete this prezi?

Neither you, nor the coeditors you shared it with will be able to recover it again.

DeleteCancel

Make your likes visible on Facebook?

Connect your Facebook account to Prezi and let your likes appear on your timeline.
You can change this under Settings & Account at any time.

No, thanks

Phase Rule and Binary Phase Diagram

No description
by

Katherine Potter

on 3 September 2012

Comments (0)

Please log in to add your comment.

Report abuse

Transcript of Phase Rule and Binary Phase Diagram

Fractionation , Fractional Crystallization Evolution of Magmas Systematic Variations in Chemical Composition Result from Crystallization of Observed Minerals 'Fractional Crystallization' Trend of liquid in compositional space Liquid Line of Descent Example: MgO Content in the Parent Basalt (< 10%) Removal of Olivine (50 % MgO) and Augite (14 % MgO) LOWERS MgO in the Resulting Magma Definitions: PHAse rule and binary phase diagrams Parent
Basalt 10%
Mgo 0.05*50% MgO = 2.5% 5% Olivine 8% Augite 0.08*14% MgO
= 1.1% = Daughter Basalt = (10-2.5-1.1)/.87 = 7.33% MgO Solidus:
Solid only below, liquid + solid below Components:
Minimum number of chemically distinct species needed to describe system Liquidus:
In P-T space, represents maximum solubility of solid in liquid
Liquid only above, solid + liquid below Eutectic:
Mixture of phases with lowest possible melting point for those components.
Refers both to the Eutectic Composition and to the Eutectic Temperature. F = c - p + 2
Closed system at equilibrium Phase rule of j. willard gibbs F =
Variance or degrees of freedom
Equals number of intensive variables needed to constrain system (T, P, or composition X) c = Components p = Phases 2 = Temperature and Pressures Condensed phase rule =
isobaric or isothermal F = c - p + 1 (P or T fixed) c = 1; p = 1
F = 1 - 1 + 2 = 2 Unary systems
= 1 component T and P both can vary,
Divariant c = 1; p = 2
F = 1 - 2 + 2 = 1 T or P can vary
Univariant c = 1; p =3
F = 1 - 3 + 2 = 0 T and P both fixed
Invariant Olivine (Forsterite-Fayalite) BINARY SOLID SOLUTIONS ISOPLETH = Constant Composition PROPORTIONS Calculated from LEVER RULE Plagioclase (Anorthite-Albite) COMPOSITIONS read DIRECTLY off the BOTTOM scale on Diagram (%An) Equilibrium Crystallization:
Final Plagioclase = Bulk Composition Fractional Crystallization:
Liquid and Plagioclase both evolve to compositions more sodic (Na-rich) than bulk composition of system. % crystals = (100 * ab)/ac (cc) photo by medhead on Flickr % liq = (100 * bc)/ac Diopside-Anorthite system (A = Diopside, B = Anorthite) SIMPLE BINARY EUTECTIC WITH NO Solid Solution Compositions from bottom of diagram
%A or %B (Both Crystals and Liquid) PROPORTIONS FROM LEVER RULE: % xtls = (100 * a)/(a+b)% liquid = (100 * b)/(a+b) Equilibrium crystallization = Fractional crystallization >> Liquid Follows Continuous Path >> Crystal Compositions “Jump” But Equilibrium melting NOT = Fractional melting Equilibrium melting:
>> Liquid, Crystals Follows Continuous Path Fractional melting:
>> Crystals Follows Continuous Path
>> Liquid Compositions “Jump” Example: System Forsterite-SiO2 (A=Forsterite, B=SiO2, AB=Enstatite) PERITECTIC SYSTEMS R = Reaction Point or “Peritectic” Phase Rule at Peritectic: F= 2-3+1= 0 Invariant EQUILIBRIUM CRYSTALLIZATION: BC X : Ol+L, Ol+En+L (at Peritectic), Stop at Peritectic (Final= Ol+En) BC Y : Ol+L, Ol+En+L (at Peritectic), En+L, En+SiO2 (at Eutectic) How do we know which final assemblage? >> If Bulk Comp to Left of AB, Final Assemblage Must = A + AB.
>> If Bulk Comp to Right of AB, Final Assemblage Must = AB + B. FRACTIONAL CRYSTALLIZATION: BOTH BC X & BC Y: OL+L --> EN+L (at Peritectic) --> En+SiO2+L (Eutectic) WHY ?? NO olivine to react with liquid during fractional crystallization. System:
Isolated part of Universe
Open to energy exchange
(usually) Closed to matter exchange
Full transcript