#Geology #PhaseDiagrams #Binary #EutecticSystem #IgneousPetrology • Phase diagrams are graphical representations of the equilibrium relationships between minerals (or others phases). These relationships are governed by the laws of thermodynamics.
Standard phase diagrams show how phases or phase assemblages change as a function of temperature, pressure, phase composition, or combinations of these variables.
• Eutectic point is the lowest possible melting mixture of the two minerals and is known as a eutectic after the Greek word Eutektos, meaning “easily melting.”
• Eutectics are the most important physical-chemical relation in igneous
petrology. Earth does not have extra heat and melting is a rare occurrence.
4. The system isobaric (atmospheric pressure) T-X phase diagram.
5. In this type of system, there is a low point on the liquidus,
point E, called the eutectic point. Such systems are thus
called binary eutectic systems. Because there is no solid
solution, there is no solidus (although some petrologists
refer to the line F-I as a type of solidus)
6. Liquid1 = Solid + Liquid2 at Liquidus (Continuous Reaction)
7. Liquid = Diopside + Anorthite at E (Discontinuous Reaction)
This type of reaction is a discontinuous reaction because it takes place at a fixed temperature until one phase is consumed (Liquid)
8. the final liquid to crystallize must always be at the eutectic composition and temperature.
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