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Shivam Sharma posted an Question
August 31, 2020 • 17:25 pm 30 points
  • CSIR NET
  • Earth Sciences

Study the textural relations given below: schistosity (muscovite+ biotite) garnet chlorite staurolite in what sequence are the minerals garnet, chlorite and sta

Study the textural relations given below: Schistosity (muscovite+ biotite) Garnet Chlorite Staurolite In what sequence are the minerals garnet, chlorite and staurolite formed? Give reasons for your answer. Two pelitic rocks, A and B, contain the following assemblages: A:Quartz-sillimanite-garnet-muscovite-biotite-graphite B: Quartz-sillimanite-garnet-K-feldspar-biotite-graphite Which of the two can be called a 'khondalite', and why?

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    Rahul kumar Best Answer

    1. Sequence of mineral formation from oldest to youngest is: Chlorite, Garnet, Staurolite. Reason: Schistosity is cutting across the Staurolite grain and warping around the garnet grain which means garnet was present before the Schistosity event and Staurolite has formed after the Schistosity event so, Staurolite formed after the garnet. Again, chlorite is an inclusion in the garnet and an inclusion is always older than tha hosting grain so chlorite must be older than garnet; so, the correct sequence from older to youger is Chlorite, garnet, Staurolite. 2. Khondalite is high grade metamorphic rocks so muscovite must have break down to form k-feldspar; Assemblage B containing K-feldspar is correct mineral assemblage of a khondalite rock.

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