Geology 443 Igneous-University of Calgary

Igneous Petrology

This is an “extension” of Geology 311 (Mineralogy and Rocks) at the University of Calgary. The foundation for these two particular subjects can be found in Geology 311 Midterm and Geology 311 Final pages. Other 300 and 400-level classes such as Structural Geology and Advanced Mineralogy will also help you out. On this page, ONLY the advanced materials are empathized because I do not think it is productive to repeat information from junior classes. Visit this page for Metamorphic Petrology

Geology (GLGY 443-UCAL) Midterm

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Question 1

Which of the following magmas would you expect to have the highest viscosity?

A	Basaltic magma
B	Rhyolitic magma
C	Andesitic magma
D	Magmas with very high water content

Question 2

Melting of mantle will predominantly produce Peridotites.

A	True
B	False; it depends on the amount of hydrous minerals in the magma.
C	False; it depends on the magma temperature.

Question 3

This is an image of poikilitic texture. Assume the mineral in the middle formed first. What is the general term given to the first formed (middle), mineral?

XPL

A	cumulate
B	poikili
C	mound
D	chadacryst
E	oikocryst

Question 4

According to Winter, Magma generation is controlled by how many plate tectonics settings?

A	5
B	4
C	3
D	6
E	7

Question 5

Melting of rocks partially, as opposed to completely, known as...

A	Dry solid melting
B	congruent melting
C	incongruent melting
D	Wet solid melting
E	solid solution melting

Question 6

Solubility of fluids are __I__ at high pressures which results in __II__ in solidus temperature.

A	I. lower II. increase
B	I. lower II. decrease
C	I. higher II. decrease
D	I. higher II. increase

Question 7

What is pseudomorphism?

A	Caused by mixing of magma from two or more (different) sources.
B	A condition in which a mineral exhibit of properties of another (hence making identification impossible).
C	Growth of a new mineral by replacing another with the shape of the original mineral.
D	Growth of a secondary mineral as a result of hydrothermal fluids.
E	A difference in chemical structure but with the exact same chemical formula.

Question 8

What causes the Ludwig-Soret effect in magma chambers?

A	Liquid Immiscibility
B	Magma Mixing
C	Thermogravitational Diffusion
D	Fractional Crystallization
E	Assimilation

Question 9

In the early days for igneous petrological studies, there were two major groups of Geologists on the "basalt issue". What were they?

A	Werners and Huttons
B	Werners and Abrahams
C	Neptunist and Plutonists
D	Chills and Hards

Question 10

Why foliations are rarely developed in igneous rocks?

A	The crystals has been already formed by the time igneous rocks undergo change in directional forces.
B	The isotopic chemical configurations would not allow foliation to be formed in igneous rocks. Hint: Dude, WTF? This won't even make sense!
C	The stresses (forces) are either two weak or non-existent in igneous environments.
D	The liquid nature of igneous rocks cannot sustain substantial directional stressed.

Question 11

Which of the following is true about hydrous minerals in the Earths' crust?

A	The volatiles are always ionically bonded.
B	The volatiles are in free form.
C	The volatiles are in the saturated form.
D	The volatiles cannot be released unless the pressure is decreased. Hint: Nope; it is opposite. The pressure increase will result in the release of volatiles.
E	The volatiles are always in the form of pure water.

Question 11 Explanation:

Note: Volatiles are mostly composed of water. However, rarely pure water.

Question 12

Which of the following is the most common in the upper mantle?

A	Pyroxenes (ortho/clino)
B	Lherzolite
C	Olivine
D	Websterite
E	Precipitates

Question 13

There are two stages to formation of minerals. What is the first stage?

A	Differentiation of ions.
B	Addition of chemical materials.
C	Radiation of energy out of a undefined nucleus.
D	Nucleation of embryos of crystals.
E	Release of ions from the nucleus.

Question 14

Typically higher the temperature, lower the viscosity.

A	False
B	True

Question 15

What would cause a magma to rapidly increase in it's viscosity?

A	Slow rate crystallization.
B	Sudden increase in temperature.
C	Increase in pressure.
D	Removal of volatiles.
E	Gradual increase in temperature.

Question 16

In the two-layer dynamic mantle model (1988), which part has the capability to produce igneous materials?

A	Outer core
B	Inner core
C	Upper layer
D	D-layer

Question 16 Explanation:

In this model, there is a 660-km transition distance between the surface and the D-layer. Subducted materials will sink into the D-layers where it may be heated by the core and brought back to the surface.

Question 17

An accurate NORM analysis can be done on any type of igneous rock.

A	False; only on rocks that has no hydrous minerals in the original melt.
B	True
C	False; only on rocks that formed in volcanic environments.
D	False; only on rock samples that crystallized at shallow low pressure environments.

Question 18

What most likely causes the slope reversal of the solidus? (eg. having a negative slope to a positive slope in the same reaction) Hint: PV = nRT and P/T = s/V

A	Addition of volatiles to the magma by hydrous minerals.
B	Change in the chemical composition of the magma due to magma mixing from another source.
C	Decrease in pressure and increased in temperature.
D	Change in the state of the material from gas to liquid or vice versa.

Question 18 Explanation:

This is a bit difficult question to answer. The Basalt solidus curve is a very good example in which the direction of the slope changes dramatically. The most common type of slope changes are often gradual. Remember gases expands and occupy a larger volume than liquid with the same number of atoms.

Question 19

Which part of a Komatiite flow should be used for melt composition analysis?

A	Chilled margins
B	Platy-spinifex area
C	Cumulative zones
D	Random-spinifex area

Question 20

During the nucleation process, if the temperature goes below the favorable conditions for forming a mineral, it will most likely result in formation of...

A	small number of large crystals.
B	glass.
C	ions.
D	random nuclei.
E	large number of small crystals.

Question 21

In __I__ , the nuclei form independently while in __II__ , the nuclei form on a per-existing crystal.

A	I. thermal II. epithermal
B	I. epithermal II. thermal
C	I. homogeneous II. heterogeneous
D	I. heterogeneous II. homogeneous
E	I. low-energy II. high-energy
F	I. high-energy II. low-energy

Question 22

How would you differentiate between the normal zoning from reverse zoning of a mineral?

A	By using the Birefringence difference between each rim.
B	By using the Reflective Indexes (Becke line test)
C	By using the XRF or in situ chemical analysis.
D	By adding a dye to a thin section and analyzing the variation in the intensity of colours.

Question 23

In modal mineralogy, we use ____ for analysis. (choose the best answer)

A	chemical composition variations
B	volumetric proportions of minerals
C	radio active dating
D	density of the whole rock
E	x-ray analysis

Question 24

What does the Clausius–Clapeyron relation (also known as "Clapeyron equation") prove?

A	All solids will eventually turns to liquids at high temperature.
B	Dry materials have a lower temperature solidus. Hint: True; but that's not what this equation proving.
C	Solidus and liquidus varies with material composition. Hint: True; but that's not what this equation proving.
D	All solids at low pressure will melt at low temperature.

Question 25

What is undercooling (with respect to magma)?

A	It is a magmatic process in which inhibits crystal formation completely.
B	It is the process of cooling a magma below the melting point by forming crystals.
C	It is the process of cooling a magma below the parental temperature but still maintain the temperature above the melting point.
D	It is the process of cooling a magma below the melting point without producing crystals.

Question 26

What is the most likely cause for wet-solidus (water saturated) based melts?

A	Dehydration of rocks due to the rapid decompression at the melting locale (location).
B	The dehydration of minerals below the melting locale (location).
C	Addition of water through the oceans in Mid Ocean Ridges.
D	The leakage of water from above (the melting locale) due to surface and groundwater runoff.
E	The dehydration of rocks above the melting locale (location).

Question 27

Which of the following statements are valid for ultramafic rocks?

A	They are highly rich in quartzs and quartzites.
B	Contains no plagioclase feldspars.
C	They are mostly associated with pyroclastic materials.
D	All rocks that contains over 70% of mafic minerals are ultramafic rocks. Hint: Nope; must be over 90%
E	Contains very high percentage of plagioclase feldspars.

Question 28

What is the primary transportation mechanism of melt (transport it to the surface)?

A	Passive gravity
B	Variations in temperature within a magma
C	Pressure variations
D	Geothermal gradient
E	Density variations

Question 29

Which of the following would be an extrusive rock?

A	phaneritic rock
B	large grained rock
C	aphanitic rock
D	peloidal rock

Question 30

A NORM analysis report indicates that there is a very high rate of quartz. As a Geologist, which of the following statements would you agree with?

A	This particular rock sample was formed in a volcanic environment.
B	This particular rock sample was formed from a purely silica based magma.
C	This particular rock sample was formed from a silica under saturated magma.
D	This particular rock sample was formed from a silica over saturated magma.
E	This particular rock sample was formed from an ultra mafic magma.
F	This particular rock sample was formed in a plutonic environment.

Question 31

Viscosity can be best described as...

A	...the ability for materials to flow.
B	...a property that only applicable to 100% pure liquids.
C	..,a property that is directly related to density of the material.
D	...the ability of materials to resist shear stress (forces).
E	...a measurement which can be calculated using mole fractions of solids and liquids in a magma.

Question 32

How much of the melting at modern day Mid Ocean Ridges attributed to decompression melting?

A	~ 15 - 20 %
B	~ 40 - 50 %
C	~ 90 - 99 % (almost all of it)
D	~ 70 - 80 %
E	0 % (none)

Question 33

Rocks with a SiO₂ composition over __A__ wt. % is classified as a/an __B__.

A	I. 66 II. acidic
B	I. 66 II. ultrabasic
C	I. 45 II. intermediate
D	I. 45 II. basic

Question 34

When using NORM for chemical analysis, which of the following must be true?

A	The rock must have a mafic origin.
B	The rock must have a plutonic origin.
C	All silica weight percentages were taken out from the analysis.
D	Hydrous minerals are taken out from the analysis.
E	The rock must have a volcanic or pyroclastic flow origin.

Question 35

Equilibrium favored more in slow cooling magma than the faster counterpart.

A	False
B	True

Question 36

When classifying igneous textures, what principle group will include nucleation?

A	primary
B	tertiary
C	secondary
D	quaternary

Question 37

During Archean __I__ was melted to produce rocks as opposed to modern day it is the __II__.

A	I. solid rocks II. crust
B	I. crust II. mantle
C	I. mantle II. crust
D	I. solid rocks II. mantle
E	I. outer core II. mantle

Question 38

Spinifex texture is an indicative what type of flow?

A	Volcanic mud flow
B	Grass flow
C	Komatiite flow
D	Pyroclastic flow
E	Spinifex flow

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You may download this exam as a PDF file here.

Credits: Based on the excellent class notes provided by, Igneous: Dr. Rajeev Nair and Metamorphic: Dr. David Pattison during Winter 2014.
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Also visit: Petrology Media Library

List of concepts

Igneous Petrology

Formation of igneous rocks and their compositional variations.
Difference between MORB and OIB basalts.
Difference between mafic and felsic magma (and processes).
Magma differentiation and layered mafic intrusions.
Physical and chemical properties
Geochemical processes (magma differentiation, isotopic variations, melting and cooling, etc), phase equilibria and geothermobarometry
Classifications and textures.
Other processes such as island arcs and continental flood basalts.

Metamorphic Petrology

What are metamorphic rocks and how do they differ from igneous and sedimentary rocks?
What is petrology?
Differences between stress, strain and pressure dynamics.
Hydrostatic and lithostatic pressures and the orientations of sigma-1,2,3.
Difference between lineation of foliation.
Metamorphic textures and structures; deformation, P-T driven textural changes, grain size and shape, grading (graded beds/layers), inclusions, etc.
History and current condition of rocks.
Classifications and textures.

Sanuja Senanayake

Geology 443 Igneous-University of Calgary

Igneous Petrology

Geology (GLGY 443-UCAL) Midterm

Also visit: Petrology Media Library

List of concepts

Igneous Petrology

Metamorphic Petrology

Standing on the shoulders of giants

Igneous Petrology

Geology (GLGY 443-UCAL) Midterm

Also visit: Petrology Media Library

List of concepts

Igneous Petrology

Metamorphic Petrology

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Standing on the shoulders of giants