UPSC Mains GEOLOGY-PAPER-II 2018

Five-fold rotational symmetry is not possible in minerals' justify the statement.

Explain the symmetry elements in a stereogram of general form {hkil} in the hexagonal-scalenohedral class.

Explain the role of decompression in magma generation.

Illustrate with neat sketches the formation of porphyritic and ophitic textures in gabbroic rocks using suitable binary phase diagram of pyroxene and plagioclase feldspar.

What are sparry allochemical carbonate rocks? Comment on their depositional environment.

Illustrate with neat sketches internal structure of pyroxene group of minerals. Give a generalized classification of pyroxene group based on composition.

Illustrate with neat sketches internal structure of calcite. How would you explain the differences in the internal structure of calcite and its polymorph aragonite?

Explain with the help of indicatrix diagram how the birefringence of a uniaxial mineral depends on crystallographic orientation of the mineral thin-section when studied under petrological microscope.

What are continental flood basalts? Illustrate with example from India. Discuss the petrogenesis and tectonic significance of such basalts.

Illustrate with appropriate mineral reactions prograde metamorphism of argillaceous sedimentary rocks.

What are migmatites? Comment on their origin.

Illustrate with neat sketches primary sedimentary structures in sands from bed load transport. How such structures can be used for interpretation of depositional environments?

Give a generalized classification of sandstone. State genetic significance of such classification.

Why are 'fining upward' facies sequences considered as one of the most important criteria for recognizing deposits of meandering fluvial depositional system?

Calculate the wt.% of iron in the following minerals, and arrange these minerals in order of increasing iron content. (Atomic weight of Fe = 56, Cr=52, Ti = 48 and O = 16) Ilmenite, magnetite, chromite, hematite.

Describe the geology of Neyveli lignite deposit and the unique problem in mining of this deposit.

What are the types of samples collected and analysed in geochemical exploration programmes? Which one of these samples is generally preferred and why is it preferred?

Explain the process of mineral beneficiation by froth flotation and its application for sulphide ores.

Calculate the average grade (wt.% Mo) of the vein.

Give the classification of meteorites. How does the study of meteorites help in understanding the internal composition of the Earth?

Illustrate different type of mass wasting processes with suitable examples. Enumerate preventive measures for the mitigation of hazards from mass wasting.

What are the sources of groundwater pollution? Suggest preventive measures to control groundwater contamination.