Anukruti posted an Question
August 01, 2020 • 15:24 pm 30 points
  • IIT JAM
  • Geology (GG)

Question (in attached picture)

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    Sajan sarthak Best Answer

    olivine will crystallising so The (Mg2Sio4 ) so 2 Mg means more mg is getting crystallized and 1 SiO2 means less sio2 will form . then the residual melt will have low mg and high si02 then option c will be the answer

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    explain again.

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    Olivine is getting crystallized components are given that Mgo and SiO2 . So forstrite i.e Mg2Sio4 will form Then 2 mole mg will crystllise while 1 mole SiO2 will crystllise then that melt will have less mg and high si02 so the arrow will be from the high mg to low mg and low si to high si ( of that residual melt)

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    Rahul kumar best-answer

    Ans- (C) Residual melt will enrich in SiO2 with crystallization of Mg2SiO4 Mg2SiO4 contains 2MgO and 1SiO2 Consider the following data of residual melt: MgO SiO2 residual melt MgO% & SiO2% 0.30 0.70 30 70 0.20 0.65 23.5 76.5 0.10 0.60 14.3 85.7 0.05 0.575 8 92 Plotting the data of MgO% and SiO2% will generate a curve as shown in option (C) Please ask in case of any doubt.

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    where did u get this data from??

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    You can generate this data yourself. As I have mentioned that Mg2SiO4 contains 2MgO and 1SiO2, so during crystallization of Mg2SiO4, 2 parts of MgO will account for one part of SiO2. The initial data of melt fraction given in question is 0.3 MgO and 0.7 SiO2. If 0.05 Mg2SiO4 will crystalline then that will take 0.05 SiO2 and 0.1 MgO, so after crystallization of 0.1 Mg2SiO4 you will have only 0.2 MgO and 0.65 SiO2 (because initially it was 0.3 MgO and 0.70 SiO2). Successive crystallization of Mg2SiO4 will deplete the melt in MgO and enrich in SiO2 and you can generate the data in same way.

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    thank u

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