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

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

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

Question 2

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	Change in the state of the material from gas to liquid or vice versa.
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	Addition of volatiles to the magma by hydrous minerals.

Question 2 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 3

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

A	4
B	7
C	6
D	5
E	3

Question 4

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

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

Question 5

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

Question 6

Why foliations are rarely developed in igneous rocks?

A	The stresses (forces) are either two weak or non-existent in igneous environments.
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 liquid nature of igneous rocks cannot sustain substantial directional stressed.
D	The crystals has been already formed by the time igneous rocks undergo change in directional forces.

Question 7

What causes the Ludwig-Soret effect in magma chambers?

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

Question 8

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

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

Question 9

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

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

Question 9 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 10

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 11

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

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

Question 12

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 silica under saturated magma.
C	This particular rock sample was formed in a plutonic environment.
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 from a purely silica based magma.

Question 13

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	chadacryst
B	mound
C	oikocryst
D	poikili
E	cumulate

Question 14

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

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

Question 15

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

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

Question 16

Melting of mantle will predominantly produce Peridotites.

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

Question 17

Which of the following would be an extrusive rock?

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

Question 18

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

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

Question 19

Spinifex texture is an indicative what type of flow?

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

Question 20

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 rock samples that crystallized at shallow low pressure environments.
D	False; only on rocks that formed in volcanic environments.

Question 21

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

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

Question 22

Viscosity can be best described as...

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

Question 23

Which of the following statements are valid for ultramafic rocks?

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

Question 24

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

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

Question 25

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

A	True
B	False

Question 26

What is undercooling (with respect to magma)?

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

Question 27

Typically higher the temperature, lower the viscosity.

A	True
B	False

Question 28

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

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

Question 29

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

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

Question 30

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

Question 31

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

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

Question 32

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

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

Question 33

What is pseudomorphism?

A	Caused by mixing of magma from two or more (different) sources.
B	A difference in chemical structure but with the exact same chemical formula.
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 condition in which a mineral exhibit of properties of another (hence making identification impossible).

Question 34

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

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

Question 35

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

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

Question 36

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

A	secondary
B	tertiary
C	primary
D	quaternary

Question 37

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

Question 38

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

A	The volatiles are in free form.
B	The volatiles are always ionically bonded.
C	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.
D	The volatiles are always in the form of pure water.
E	The volatiles are in the saturated form.

Question 38 Explanation:

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

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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