need some help answering part b thanks 27. Below is the phase diagram for the pl

Question

need some help answering part b
thanks

27. Below is the phase diagram for the plagioclase solid solution. a. Label the solidus and the liquidus b. For liquid composition X that is cooling: i. What is the composition of the liquid? ii. What is the composition of the first crystals to form? ili. What is the composition of the last crystals to form? 1600 Liquid 1400 1200 Plagioclase Liquid soldys Plagioclase 1000 800 0 20 40 60 80 100 NaAISi3O8 Ab %An CaAbSi2O An http://www.tulane.eduw-sanelson/images/plagphasediagram.ai

Explanation / Answer

b.1.As we know we start a solid solution with a liquid which contains both the crystal composition so the composition is 50%Ab and 50% An.

2.As shown in the figure that the first crystal formed at 1500°c which is indicated as plagioclase but it is on the Anorthite side so the composition would be CaAl2Si2O8

3.Last crystal is formed at 900°c and it is on the albite side so the composition would be albite with chemical composition NaAlSi3O8.

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