Imagine that at this point in the crystallization sequence (when the ratio of cr

Question

Imagine that at this point in the crystallization sequence (when the ratio of crystals to melt is 1:1), all the crystals settle to the bottom of the magma chamber and cease to react with the melt (ope system!). After this, the remaining melt crystallizes in the normal way, with crystals and melt remaining in equilibrium.

Question: Draw a new isopleth for the system and label it I2.

GEOSC 201 - Spring 2016 Plagioclase Solid Solution Phase Diagram Due Friday, February 19 Use the diagram below to answer the Bram below to answer the following questions. IMPORTANT: Be sure to n the appropriate lines on the phase diagram! Do not attempt to answer the actions without doing so. Use a ruler or other straight edge to make your lines. mistakes (i.e., crooked lines) will cause you to arrive at incorrect answers. If you do not show your work (draw the lines!), you will not receive full credito 1600 1553 ** Consider a silicate melt that has the composition An50.** 1500 1. Draw the isopleth and label it Ii. 1400 solidus TEMPERATURE, °C PLAGIOCLASE + L. 2. As the melt cools, at what temperature do the first crystals begin to form? 1300 1200 PLAGIOCLASE CRYSTALS 3. What is the composition of those first crystals? 11180 1100 O 80 40 60 WEIGHT PERCENT An 100 An

Explanation / Answer

1) ATTACHED IMAGE SHOWS THE CRYSTALIZATION PATH HAVING An 50 COMPOSITION.

2) First crystal form at 1410 0C.

3) Anorthite having composition at B point in image attached approx An8

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