UPSC Mains GEOLOGY-PAPER-II 2013

Explain how the radius ratio of cation to anion influences coordination in minerals. Cite examples of two common coordination in rock forming minerals.

Define the Gibbs phase rule and calculate the variance of the assemblage containing enstatite + forsterite + Mg-spinel + Mg-cordierite + corundum in the appropriate chemical system.

With suitable examples, enumerate the essential difference between regional dynamothermal metamorphism and contact metamorphism.

Explain why in any igneous rock, primary forsterite and quartz cannot stably coexist.

Describe the critical differences between porosity and permeability. Add a note on how these two properties of sediments are determined.

With theoretical details, discuss optical indicatrix, and determination of sign of elongation of uniaxial minerals.

With suitable examples, discuss the causes behind and effects of pleochroism and birefringence in minerals.

Derive Bragg's law for X-ray diffraction. Calculate the inter-planar spacing in a crystal for a plane that gives a sharp reflection at 20 = 50° for CuKa radiation (A = 1-5418 Å) in a powder X-ray diffraction experiment.

Thin sections of three basaltic rocks contain phenocrysts of Ca-rich plagioclase in diopside matrix, phenocrysts of diopside in Ca-rich plagioclase matrix, and coexisting phenocrysts of both Ca-rich plagioclase and diopside. On the basis of phase diagram in the diopside-anorthite system, describe the initial melt composition and temperatures, along with crystallization behavior of the above rocks.

By suitable reactions, discuss various mineralogical and mineral-chemical changes that take place during metamorphism of a basaltic rock at the greenschist-amphibolite facies transition.

In a P-T diagram show the domains of various metamorphic facies and briefly explain these facies.

What are turbidites ? With a neat sketch, show different units of a Bouma cycle and the flow regimes under which they are formed.

With neat sketches, describe the primary depositional sedimentary structures, with emphasis on their application in determining paleocurrent directions.

With the help of a neat sketch, briefly discuss the classification of sandstone. What is the general tectonic environment in which quartz arenites are found?

Describe the relationship between average crustal abundance of metals and their content in ore deposits. Add a brief note on tonnage, grade and cut-off grade of ore deposits.

What are the sources for the formation of coal and petroleum deposits ? Briefly discuss the process of coalification.

Briefly enumerate the various sampling methods in mineral exploration and mining.

From the first and the second laws of thermodynamics and assuming reversible process, derive the expression dU = TdS - PdV; where U, S, T, P and V respectively stand for internal energy, entropy, temperature, pressure and volume.

Discuss the various causes and environmental impacts of acid mine drainage.

Explain the ore forming processes that result in chromite and Ni-Cu sulphide deposits hosted by ultramafic rocks.

With schematic sketches, show and elucidate the zones of hydrothermal alteration in a porphyry copper deposit, emphasizing their mineralogy and temperature of alteration. Explain why the ore zone is localized at the boundary between two specific alteration zones.