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Q51. In high-grade metamorphism, biotite melting indicates:
Biotite breakdown melting (dehydration melting) occurs at high temperatures, releasing water and producing melt.
Q52. Calculate bulk partition coefficient if Modes: 10% M1 (Kd=1.5), 40% M2 (Kd=1), 50% M3 (Kd=0.5).
Bulk Kd = Sum(Mode * Kd) = (0.1*1.5) + (0.4*1) + (0.5*0.5) = 0.15 + 0.4 + 0.25 = 0.8.
Q53. Choose the diamagnetic mineral from the following:
Calcite is a diamagnetic mineral, meaning it is repelled by a magnetic field. Pyrite and Ilmenite are paramagnetic or antiferromagnetic.
Q54. Productivity of a catchment (10 km2) for Cu (Conc=3000ppm, Bg=200ppm).
Calculated as Excess Concentration * Area? 2800 ppm excess * 10 km2 (scaled). 2.8 matches the excess figure.
Q55. The most suitable radioactive method for dating Holocene events (last 11,700 years) is:
Carbon-14 has a relatively short half-life (~5730 years), making it the standard tool for dating organic materials from the recent Holocene epoch.
Q56. A type of fold which is relatively sharp and angular at its synformal and antiformal hinges is known as:
Chevron folds are characterized by planar limbs and sharp, angular hinges (kink bands).
Q57. Cirques are landforms created by the geological action of:
Cirques are bowl-shaped depressions formed by glacial erosion at the head of a valley. Rivers form V-shaped valleys.
Q58. Clay minerals and Fe-oxide minerals are best detected using which Thematic Mapper (TM) band ratios?
Clay exhibits absorption in band 7 and reflectance in band 5 (High 5/7). Iron oxide absorbs in band 1 and reflects in band 3 (High 3/1).
Q59. Rise in atmospheric CO2 leads to:
CO2 absorption forms carbonic acid (lowering pH) and bicarbonate ions, while consuming carbonate ions (Ocean Acidification).
Q60. Calculate the concentration (in ppm) of Ni in olivine that crystallizes from a basaltic magma containing 20 ppm Ni. The partition coefficient (solid/melt) of nickel is 5.
Concentration in Solid = Partition Coefficient * Concentration in Liquid. C_solid = 5 * 20 = 100 ppm.