28. The minerals formed at the highest grade (the peak) of metamorphism are pres

Question

28. The minerals formed at the highest grade (the peak) of metamorphism are preserved during uplift & erosion because: a) pressure is released after the peak b) high grade minerals remain stable d) fluids are absent after the peak c) temperature increase until the rocks surface 29. Metamorphism produces the following changes in rocks: a) partial melting b) recrystallization c) change in mineralogy d) change in chemical composition e) b) and c) 30. How do geologists know what minerals are stable for a given composition at a particular T and P condition? They use: a) the periodic table b) the results of experiments c) a long thermometer d) their intuition e) they guess

Explanation / Answer

Ans 28:- Minerals that are formed at the highest grade, with the increasing grade hydrous minerals by losing water become less hydrous and non hydrous minerals come in existance. Thus the option d is the correct ans

Ans 29 :- The IUGS has proposed the following definition of metamorphism " a process involving changes in the mineral content/composition and/or microstructure of the rock, dominantly in the solid state. This process is mainly due to an adjustment of the rock to physical conditions that differ from those under which the rock originally formed and that also differs from the physical conditions normally occuring at the surface of the earth and in the zone of diagenesis. The process may co exist with partial melting and may also involve changes in the bulk chemical composition of the rock. According to this definition option e is the most appropriate ans.

Ans 30 :- In the scientific world all the knowledge and final results are the outcome of experiments. option B is the ans according to me.

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