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Q111. A type of unconformity characterized by the occurrence of sedimentary rocks on igneous/metamorphic rocks is known as:
Nonconformity occurs when sedimentary rock rests on top of older eroded igneous or metamorphic rock.
Q112. The correct chronological order (older to younger) of these volcanic events: (P) Rajmahal, (Q) Deccan, (R) Panjal, (S) Malani.
Order: Malani (Precambrian) -> Panjal (Carboniferous-Permian) -> Rajmahal (Early Cretaceous) -> Deccan (Late Cretaceous).
Q113. Which one of the following stable isotopic ratios is used for estimation of palaeo-temperature of seawater?
Oxygen isotope fractionation (d18O) in foraminifera shells is the standard proxy for reconstructing past ocean temperatures.
Q114. Which mineral assemblage is stable in a pelitic rock in the greenschist facies?
Pelitic rocks (Al-rich) in greenschist facies typically contain muscovite, chlorite, biotite, and quartz. Albite/actinolite is for mafic rocks.
Q115. Calculate the degree(s) of freedom of the assemblage Opx + Cpx + Plag + Hbl + Qtz + Fluid in the 6-component system CaO-FeO-MgO-Al2O3-SiO2-H2O.
Phase Rule: F = C - P + 2. Components (C)=6. Phases (P)=6. F = 6 - 6 + 2 = 2.
Q116. Identify the microscope component using: Pleochroism of biotite.
Pleochroism is observed in Plane Polarized Light (Analyzer removed). Rotating the stage changes absorption relative to the Polarizer direction.
Q117. Which option represents porosity of a rock?
Porosity = Pore Volume / Bulk Volume. Since Pore Vol = Bulk Vol - Solid Vol, the formula is (V_bulk - V_solid) / V_bulk.
Q118. Water content = 10%, Porosity = 25%, Specific Gravity = 2.5. Volume of water to add to 100 m3 of soil for full saturation (in m3)?
Porosity 25% means 25m3 voids per 100m3. Dry density = 2.5 * (1-0.25) = 1.875 g/cc. Mass dry = 187.5 tons. Current water (w=10%) = 18.75 tons = 18.75 m3. Pore volume = 25 m3. Water needed to fill pores = 25 - 18.75 = 6.25 m3.
Q119. A phase-diagram with a specified bulk-composition is known as:
Pseudosections show stable mineral assemblages for a specific bulk composition over a P-T range. AFM/ACF are compatibility diagrams (projections).
Q120. The type of wave that arrives first at a station from an earthquake hypocenter is:
P-waves (Primary waves) are compressional waves and travel faster than S-waves or surface waves.