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Nilanjan Bhowmick AIR 3, CSIR NET (Earth Science)
Shivam Sharma posted an Question
September 01, 2020 • 17:15 pm
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30 points
30 points
- CSIR NET
- Earth Sciences
A) shown below are textures of two magmatic rocks in figures a and b. these rocks were produced by equilibrium crystallization of two separate melt compositions
a) Shown below are textures of two magmatic rocks in Figures A and B. These rocks were produced by equilibrium crystallization of two separate melt compositions. An isobaric T-composition phase diagram in the system Mg2SiO4-S102 is shown in Figure C. Mineral abbreviations used in the Figures are as follows: Opx orthopyroxene, Qtz = quartz, Olv = olivine, Fo = Forsterite, En = Enstatite, Cr Cristobalite. L = Melt. PE1atmoSphere Opx OV L opxatz Opx Opx 1557 C Qt EnsL543 C Olv Fo+En En+cr Mg,Si,O, Sio PA Figure A Figure B Mg,Sio, Figure C Now answer the following questions. () Using the phase diagram in Figure C, write the nature of melt compos itions, which has given rise to these rocks. i) Which rock in the above Figures indicates final crystallization at point Y? (6- b) (1) Calculate the variance of the point X in Figure C. (ii) What is its petrological name?
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Rahul kumar Best Answer
(a)-->(i) Look at the attached figure. Melt composition Z (in attached figure) will produce rock in figure A and melt composition X will produce rock in figure B. I have discussed the crystallization sequence in your previous question. (ii) Rock in figure A indicates the final crystallization at eutectic point Y. (b)-->(i) Variance at point X will be 0 (ii) Petrological name of point C is peritectic point (The point on a phase diagram where a reaction takes place between a previously precipitated phase and the liquid).