Analyze the rock sample in FIGURE 7.3. The parent rock for this metamorphic rock
ID: 236472 • Letter: A
Question
Analyze the rock sample in FIGURE 7.3. The parent rock for this metamorphic rock had flat layers that were folded during metamorphism. Describe a process that could account for how this rigid gneiss was folded without breaking during regional metamorphism. Analyze this metamorphic rock sample using the classification chart in FIGURE 7.16. Is this rock foliated or nonfoliated? Notice that the rock consists mostly of muscovite but also contains scattered garnet crystals. What is the name for this kind of texture? What is the name of this metamorphic rock? What was the likely parent rock (protolith)? Analyze this metamorphic rock sample using the classification chart in FIGURE 7.16. Is this rock foliated or nonfoliated and how can you tell? What is the name of this metamorphic rock? What was the likely parent rock (protolith)? REFLECT & DISCUSS Which one of the rocks in this activity do you think has the highest metamorphic grade? Explain your answer.Explanation / Answer
Answer C) Since, the rock has undergone regional metamorphism. Therefore, due to presence of high temperature and pressure the minerals of rocks behaves like ductile manner rather to break. That is why in the given sample of gneiss the minerals undergone folding rather to break.
Answer D) Part 1
The given sample of rock is foliated rock because there is orientation of muscovite can be seen on the rock.
Part 2) As the coarse crystal of garnet is surrounded by the fine muscovite groundmass, therefore the texture is porphyroblastic.
Part 3) The name of the rock could be phyllite, as the orientation of mineral muscovite can be seen on the rock.
Part 4) The protolith or source rock of this metamorphosed rock could be slate.
Answer E) part 1)
It is foliated rock, because one can easily analyse the light and dark colour mineral banding.
Part 2) The name of the rock is Gneiss, because due to the banding of light and dark colour minerals which is the diagnostic properties of Gneiss.
Part 3) The protolith of the gneiss rock would be shale or sandstone.
Answer F) As the grade of metamorphism increases the mineral orientation (low grade metamorphism) and banding(high grade metamorphism) developes in the rock. Therefore,Gneiss is the high grade metamorphic rock.