Anukruti posted an Question
January 04, 2021 • 17:09 pm 30 points
  • IIT JAM
  • Geology (GG)

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  • Owishi Sarkar best-answer

    The answer is Hornblende Granite according to IUGS classification. Refer to the images given below.

    cropped1771951899066940471.jpg
    cropped9017017144294236861.jpg
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    Rahul kumar Best Answer

    Answer: Hornblende Granite Given, Qtz= 20%, Plg= 20%, Orthoclase= 30%, Hbl= 10%, Others= 10% For IUGS classification of plutonic rocks, we have to Normalise Q (Quartz), A (Alkali feldspar), P (plagioclase) to 100%. After normalisation, the modal percentage of Q,A and P are; Q= (20/70) × 100 = 28.57% A= (30/70) × 100 = 42.85% P= (20/70) × 100 = 28.57% On IUGS classification Diagram of plutonic igneous rocks (QAPF Diagram), this modal composition will lie in the zone of Granite. So, according to the IUGS classification, this rock should be classified as Granite. Also, looking at the high modal percentage of Hornblende in the rock, the more precise name for this rock will be Hornblende Granite.

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