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1、crystalmeltphasediagracrystalmeltphasediagramsms晶体熔体相图晶体熔体相图The Gibbs Phase RuleThe phase rule allows one to determine the number of degrees of freedom (F) or variance of a chemical system. This is useful for interpreting phase diagrams.F = 2 + C - F FWhere F is the number of degrees of freedom, C i
2、s the number of chemical components and F is the number of phases in the system. The number two is specified because this formulation assumes that both T and P can be varied.Phase Rule Significance for Phase DiagramsFor two dimensional phase diagrams:Stability fields: Areas (T-P, T-X, P-X space) whe
3、re a phase or phase assemblage (more than one phase) is stable.Equilibrium boundary lines: These define the limits of stability fields. These represent values of intensive parameters where phases in adjacent fields coexist.Triple points: Points where equilibrium boundary lines meet. All phases in th
4、e adjacent stability fields must coexist.Silica Phase Diagram and Phase RuleSingle Component System: F = 2 + C - F = 3 - FStability FieldF= 1; F = 2; divariantBoundary LineTriple PointF= 2; F = 1; univariantF= 3; F = 0; invariantFrom Swamy et al., 1994Wet and Dry Melting Relations for AlbiteFrom Bur
5、ham & Davis, 1974; Boettcher et al., 1982Dry MeltingCurveWater Saturated Melting CurveWater UndersaturatedMelting Curves(2, 5, & 8 kbar)Binary Phase Relations - DefinitionsLiquidus line: the line that represents the locus of depressed freezing points as a second component is added to the system. Sol
6、id phases are not stable at temperatures above those defined by the liquidus line or surface.Di-An Binary Eutectic Phase DiagramBinary Phase Diagram DefinitionsEutectic point: Lowest T point on the liquidus at which a unique melt of fixed composition is in equilibrium with two or more phases. Isople
7、th: line of constant chemical composition.Isotherm: line of constant temperatureTie line: portion of isotherm that connects two stable coexisting phases, in this case L (representing the silicate liquid) and S (pure crystalline anorthite feldspar)The Lever RuleFollows directly from the Law of Conser
8、vation of Mass.Allows one to calculate either algebraically or graphicallythe modal abundance of each phase at every temperature.MASS OF LIQUIDMASS OF SOLIDBULK COMPOSITIONCooling History in a Binary Eutectic SystemIntersection with liquidus: F = 1 (T or X)Eutectic point: F = 0Initial State: F = 1 +
9、 C - F = 1 + 2 - 1 = 2 (T & X)subsoliduscoolingF = 1dQ/dt is constantF=1F=1F=2F=2F=2F=2F=3F=3Di-An Binary Eutectic Free Energy RelationsMgO-SiO2 Incongruent Binary Melting RelationsPeritectic point: binary systemwith 3 phases, one of whichis liquid, are in a reaction relation.At R, the reaction poin
10、t:Mg2SiO4 + SiO2 (in melt) =2MgSiO3 + latent heatEnstatite melting yields liquid richer in silica.Equilibrium vs. Fractional CrystallizationEquilibrium Crystallization:crystals continuously reactand re-equilibrate with themelt at P-T-X conditionschange. Melt-xtal reactions are reversibleFractional C
11、rystallization:Crystals are immediately isolated, removed, orfractionated from the residual melt so that nofurther reactions can occur.Melt-xtal reactions areirreversible.Binary Phase Loop with Solid SolutionliquidussolidusPlagioclase Differentiation MechanismsGabbro - Plane Polarized LightPlagiocla
12、se zoningCrystal Settlingzoned plagPerthiticpyroxeneHawaiian Basalt Phase Relations at 1 atmFrom Wright & Okamura, 1977Temperatures measured in borehole1170C1130C1075C1020CGeneralized Basalt Phase DiagramFrom Green, 1982进入夏天，少不了一个热字当头，电扇空调陆续登场，每逢此时，总会想起进入夏天，少不了一个热字当头，电扇空调陆续登场，每逢此时，总会想起那一把蒲扇。蒲扇，是记忆中的
13、农村，夏季经常用的一件物品。记忆中的故那一把蒲扇。蒲扇，是记忆中的农村，夏季经常用的一件物品。记忆中的故乡，每逢进入夏天，集市上最常见的便是蒲扇、凉席，不论男女老少，个个手持乡，每逢进入夏天，集市上最常见的便是蒲扇、凉席，不论男女老少，个个手持一把，忽闪忽闪个不停，嘴里叨叨着一把，忽闪忽闪个不停，嘴里叨叨着“怎么这么热怎么这么热”，于是三五成群，聚在大树，于是三五成群，聚在大树下，或站着，或随即坐在石头上，手持那把扇子，边唠嗑边乘凉。孩子们却在周下，或站着，或随即坐在石头上，手持那把扇子，边唠嗑边乘凉。孩子们却在周围跑跑跳跳，热得满头大汗，不时听到围跑跑跳跳，热得满头大汗，不时听到“强子，别跑
14、了，快来我给你扇扇强子，别跑了，快来我给你扇扇”。孩。孩子们才不听这一套，跑个没完，直到累气喘吁吁，这才一跑一踮地围过了，这时子们才不听这一套，跑个没完，直到累气喘吁吁，这才一跑一踮地围过了，这时母亲总是，好似生气的样子，边扇边训，母亲总是，好似生气的样子，边扇边训，“你看热的，跑什么？你看热的，跑什么？”此时这把蒲扇，此时这把蒲扇，是那么凉快，那么的温馨幸福，有母亲的味道！蒲扇是中国传统工艺品，在是那么凉快，那么的温馨幸福，有母亲的味道！蒲扇是中国传统工艺品，在我国已有三千年多年的历史。取材于棕榈树，制作简单，方便携带，且蒲扇的表我国已有三千年多年的历史。取材于棕榈树，制作简单，方便携带，且蒲扇的表面光滑，因而，古人常会在上面作画。古有棕扇、葵扇、蒲扇、蕉扇诸名，实即面光滑，因而，古人常会在上面作画。古有棕扇、葵扇、蒲扇、蕉扇诸名，实即今日的蒲扇，江浙称之为芭蕉扇。六七十年代，人们最常用的就是这种，似圆非今日的蒲扇，江浙称之为芭蕉扇。六七十年代，人们最常用的就是这种，似圆非圆，轻巧又便宜的蒲扇。蒲扇流传至今，我的记忆中，它跨越了半个世纪，圆，轻巧又便宜的蒲扇。蒲扇流传至今，我的记忆中，它跨越了半个世纪，也走过了我们的半个人生的轨迹，携带着特有的念想，一年年，一天天，流向长也走过了我们的半个人生的轨迹，携带着特有的念想，一年年，一天天，流向长长的时间隧道，袅长的时间隧道，袅结束
