IOCL-ONGC Geology Model Test Paper
Petrology Solved Test Paper
Q.1: Wall rocks surrounding a magmatic instrusion become hot by:
(a) Conduction.
(b) Convection.
(c) Radiation.
(d) Convection and radiation.
Answer. (a)
Q.2: Most of major minerals in magmatic rocks are solid solutions, except:
(a) Felspar.
(b) Quartz.
(c) Mica.
(d) Pyroxenes.
Answer. (b)
Q.3: Mark the correct statement, regarding average mineral composition of the igneous
rocks:
(a) Feldspars > Quartz > Pyroxenes and Amphyboles.
(b) Quartz > Feldspars > Pyroxenes and Amphyboles.
(c) Quartz > Feldspars > Mica > Pyroxenes and Amphiboles
(d) Feldspars > Pyroxenes and Amphyboles > Quartz > Mica.
Answer. (d)
Q.4: Mark the correct statement:
(a) The rate of crystallisation is slow in labile region.
(b) The rate of crystallisation is rapid in metastable region and slow in labile region.
(c) The rate of crystallisation is rapid in labile region and slow in metastable region.
(d) The rate of crystallisation is same in both the regions.
Answer. (c)
Q.5: The liquids represents:
(a) The upper temperature boundary of crystal-free liquid in the system.
(b) The lower temperature boundary of crystal-free liquid in the system.
(c) The composition of crystalline solid solutions coexisting with liquid.
(d) None of the above.
Answer. (b)
Q.6: A particular point at which the two components having different freezing points
crystatllise together is known as:
(a) Crystallisation point.
(b) Solidus point.
(c) Eutectic point.
(d) Liquids point.
Answer. (c)
Q.7: Which are the best examples of solid solution:
(a) Plagioclases.
(b) Plagioclases and pyroxenes.
(c) Micas.
(d) Quartz and its verities.
Answer. (b)
Q.8: The term febric of a rock includes:
(a) Texture only.
(b) Structure only.
(c) Texture and structure both.
(d) Texture, structure and mineral composition.
Answer. (c)
Q.9: Mark the correct statement:
(a) States of small molar volume are more stable at high pressure.
(b) More disordered states of high entropy are more stable at high temperature.
(c) States of small molar volume are more unstable at high pressure.
(d) Both (a) and (b).
Answer. (d)
Q.10: ln a binary eutectic system a solubility line show:
(a) The concentration of components in the liquid.
(b) Temperature in the liquid.
(c) Pressure in the liquid.
(d) Both (a) and (b).
Answer. (a)
Q.11: The role of dissolved water in silicate melts:
(a) Depolymerizes the melt.
(b) Reduces melt viscosity.
(c) Increases diffusion rates and depresses crystallisation temperature.
(d) All the above are correct.
Answer. (d)
Q.12: Crystallization of minerals in discontinuous reaction series with falling temperature is:
(a) Olivine-cIinopyroxene-onhopyroxene-Amphibole-Biotite.
(b) Clinopyroxene orthopyroxene olivine Amphibole Biotite.
(c) Olivine-orhtophyroxene-clinopyroxene Amphibole Biotite.
(d) Biotite-Amphibole-othropyroxene-clinopyroxene-olivine.
Answer. (c)
Q.13: Bowen’s reaction series indicate the process of.... in magma:
(a) Fractional differentiation.
(b) Gravity separation.
(c) Liquid immiscibility.
(d) Filter Pressing
Answer. (a)
Q.14: What is the source of the basaltic Iavas of the midoceamic ridges:
(a) Granitic rocks.
(b) Ultrafelsic rocks of the upper mantle.
(c) Ultramafic rocks of the upper mantle.
(d) lt is unkonwn.
Answer. (c)
Q.15: The amount of assimilation of cool wall rock into a magma is limited by:
(a) Pressure.
(b) Composition of wall rock.
(c) Composition of magma.
(d) Thermal energy of the magma itself.
Answer. (d)
Q.16: Emplacement of plutons is:
(a) Pretectonic.
(b) Syntectonic.
(c) Posttectonic.
(d) All the above.
Answer. (b)
Q.17: Leptynite is a:
(a) Garnetiferous granite.
(b) Calcareous granite.
(c) Tourmaline granite.
(d) Zircon granite.
Answer. (b)
Q.18: The alkaline rocks are less abundant than tholeiites because of:
(a) Smaller degree of partial melting.
(b) Difference in density and viscosity of magmas.
(c) Non-ideal behaviour in the liquids.
(d) All the above are correct.
Answer. (d)
Q.19: Which volcanic rock contains relatively high percentage of silica:
(a) Basalt.
(b) Andesite.
(c) Trachyte.
(d) Rhyolite.
Answer. (d)
Q.20: Reaction between a Pising magma and crystal with which it comes into contact is
generally termed as:
(a) Xenolith.
(b) Syntexis.
(c) Differentiation.
(d) None of these.
Answer. (b)
Q.21: The loss of volatile substances from lava causes:
(a) A rapid increase in viscosity.
(b) A rapid decrease in viscosity.
(c) No change in viscosity.
(d) None of these.
Answer. (a)
Q.22: Which one is not a discordant igneous body:
(a) Dyke.
(b) Sill.
(c) Batholith.
(d) Phuton
Answer. (b)
Q.23: Match the following:
I II
1. Batholith. i. Funnel-shaped circular outcrop.
2. Ethmolith. ii. Largest intrusive body
3. Harpolith. iii. Any irregular intrusive body.
4. Chonolith iv. Sickle-shaped basic body.
(a) 1-iii, 2-ii, 3-i, 4-iv.
(b) 1-ii, 2-i, 3-iv, 4-iii.
(c) 1-ii, 2-i, 3-iii, 4-iv.
(d) 1-i, 2-ii, 3-iii, 4- iv.
Answer. (b)
Q.24: Pahoehoe structure is related to:
a) Block lava.
b) Ropy lava.
c) Pillow structure.
d) Lava-drain tunnel. .
Answer. (b)
Q.25: ‘Rift and grain’ structure is found very predomiently in:
a) Basalt.
b) Dolerite.
c) Granite.
d) Pegmatite.
Answer. (c)
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