GEOLOGY STUDY GUIDE
Module exam GL4 June 2004
IGNEOUS ROCKS
Geology Department, Greenhead College, Huddersfield.
Your name .....…………………….................................................
Date .........……………...........
LEARNING TARGETS
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When you have completed this study guide, you will:
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Know about different igneous environments
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Know that partial melting and pressure release creates melts in the mantle and
crust
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Understand how magmas crystallise on the surface or in the crust
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Know about igneous rock mineralogy and texture
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Understand Bowen’s reaction series and the cooling history of igneous rock
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Know how magmas differentiate to produce layered intrusions.
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Module exam GL4 June 2004
Resources
Here is a choice of resources to use. You do not need to look at them all but clearly the more you read the
better your knowledge of case studies will be. Tick the box once you have used the resource.
If you read a photocopied extract then highlight it to help you reread it for revision. If you make notes
from a video tape make sure that the notes are headed with the name of the tape so that you know the
source of your information. Case studies are very useful for essay questions so you should keep a separate
list of the examples that you have researched.
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IR1
IR2
IR3
IR4
IR5
IR6
IR7
IR8
IR9
IR10
IR11
IR12
IR13
IR14
IR15
IR16
IR17
IR 18
IR 19
IR 20
IR 21
IR 22
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Understanding Geology David Webster p 139-145
Geoscience Edwards and King p. 59-68
Geological Science by Andrew McLeish p. 177-180
Video Horizon. The Day the Earth Melted. Tapes 9 and 14 50 mins
Library Video Horizon The Day the Earth Melted
Video Volcanic Iceland Tape 13 22mins
Video Christmas Lectures 1995 Tape 12 19mins
Library Video Christmas Lectures 1995
Diagrams of examples of igneous rock emplacement and intrusion
Library Video Natural World: Islands of the Fire Goddess - Hawaii
Earth Story Programme Ring of Fire Tape 35 and 39 50mins
Library Video Earth Story Programme Ring of Fire
Earth Story Programme The Deep Tape 35 and 39 50mins
Library Video Earth Story Programme The Deep
Earth Story Programme Journey to the Centre of the Earth Tape 35 and 39 50mins
Library Video Earth Story Programme Journey to the Centre of the Earth
Phase diagram exercise
Texture matrix
Video Inside Volcanoes Tapes 1, 3, 4 22 mins
Library Pitcher, W.S. The Nature and Origin of Granites
Library OU Earth Materials
Powerpoint Palisades Sill, and Skye, the Cuillins and the Red Hills
Solid Solution crystal lattice and phase diagrams
Library Kennett, P and Ross, C.A. Aspects of Geology Igneous rocks
Library Press and Siever Earth
Library Hatch, Wells and Wells Petrology of the Igneous Rocks
Powerpoint to show igneous rock textures
Websites
www.geolab.unc.edu/Petunia/VG/Mount_Airy/main.html
www.bris.ac.uk/Depts/Geol/vft/oman.html
volcano.und.nodak.edu/vwdocs/vwlessons/atg.html
www.soton.ac.uk/~imw/igneous.htm
uts.cc.utexas.edu/~rmr/
www.abdn.ac.uk/geology/profiles/auming/arran/arran.htm
There are many other websites you could search.
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Module exam GL4 June 2004
TASK 1 PLATE MARGINS
Read through your AS notes on the five different types of plate margins. For each
you should know
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diagram to show processes and features
types of igneous and volcanic rocks
type of metamorphism
depth of earthquake foci
faulting and folding (if relevant)
You will be tested on this part of the specification so it is essential to understand it
before you continue to the A2 course.
TASK 2 THE DAY THE EARTH MELTED
Watch IR 4 Make notes on the BIG IDEAS that have developed from Dan
MacKenzie’s research into the physics of the mantle. Here are some questions to be
answered:
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Why is there so much molten rock produced in the mantle?
What is the nature of the mantle?
How does the mantle flow?
How does magma move through solid rock?
What are mantle plumes?
What is the significance of the Deccan Traps in India for the understanding of
mantle plumes?
What is pressure release and why is it so important?
Why is oceanic crust a constant thickness of 6/7kms?
How does Dan MacKenzie explain the geology of the oceanic crust which
makes up Iceland?
TASK 3 IGNEOUS ENVIRONMENTS
Each igneous environment produces magma of different compositions. Read the
relevant pages in IR1, IR2 and IR3, concentrating on the types of magmas
produced at each plate margin and the processes which occur there.
There are several videos (IR 5, IR 6, IR 8, IR 9, IR 10, IR 11) which will give you a
visual image of plate margins and will add case studies such as Hawaii, the Pacific
Ring of Fire, Iceland, the Andes and the Rockies. Make time to watch at least one
of them at home.
In lesson time we will summarise your findings by going through each plate margin
in turn, using diagrams to explain how magmas are produced.
Use this box for notes
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Module exam GL4 June 2004
TASK 4 PHASE DIAGRAMS
Complete the exercise IR 12 which is based on the diagrams from IR 2 p 57-59
TASK 5 EMPLACEMENT AND EXTUSION
1. Define emplacement, intrusion and extrusion.
2. Draw a diagram to show each process and explain the difference between them
by labelling your diagram.
3. Brainstorm on the factors which you think could cause magma to rise through
the crust.
4. Discuss the importance of each factor and make class notes.
TASK 6 EMPLACEMENT OF PLUTONS, DYKES AND SILLS
Using the diagrams (IR 7) of examples of the Arran granite, the Beinn an Dubhaich
granite in Skye and the Midland Valley sill as well as your observations in Arran,
make notes on the emplacement of igneous intrusions. Be aware of the difference
between diapiric emplacement and stoped emplacement of plutons.
TASK 7 IGNEOUS COMPOSITION
IR 3 p.53 shows the composition of igneous rocks. You need to know their
mineralogy in more detail than at AS.
Redraw the table to include only the rocks you need to know, which are: granite,
microgranite, rhyolite, diorite, andesite, gabbro, dolerite, basalt and
peridotite. Add % mineral composition of each rock.
IR 2 p.56 has an interesting block diagram which shows the same information.
Which diagram will you prefer to learn?
TASK 8 IGNEOUS PRACTICAL
Use the practical sheets to draw and label specimens of the nine rocks in Task 7.
At A-level it is important to identify the mineralogy and texture of each rock. You
need to use lenses to look carefully at grain size and composition.
TASK 9 XENOLITHS
Write a report on igneous xenoliths. It will probably be about 2 sides and include
diagrams and sketches.
Your report should include the following:
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Description of several examples of xenoliths, using slides, samples and maps
An explanation of how they form, using the Law of Included Fragments to
explain the relative age of a xenolith and its igneous rock
Comment on how xenoliths change magma composition using the words
assimilation, contamination and digested
Comment on how xenolith orientation varies in diapiric and stoped plutonic
intrusions
continued..…..
Use this bo x for notes
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Module exam GL4 June 2004
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You have these resources available to you:
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A slide of a xenolith in micro-granite
Slides of Shap Granite Quarry
A specimen of a xenolith
Building Stones Guide to Huddersfield
Shop-fronts in Huddersfield (especially the Nawaab restaurant)
You could also do some research using books and CD Roms in the library.
Examples of Beinn an Dubhaich granite and Arran granite in Scotland
Deadline………………………………………..
TASK 10 IGNEOUS TEXTURES
Use IR 13 to describe igneous textures. Explain how each texture is interpreted.
Draw labelled diagrams to illustrate the texture of selected thin sections of igneous
rocks magnified x 10 through a microscope.
TASK 11 BOWEN’S REACTION SERIES
Bowen carried out experiments using magma melts in a laboratory to find out the
order of crystallisation of minerals as a magma cooled. He found that a clear
sequence was followed in theory. This is shown in IR 2 p.57 in Figure 4.5. We
will draw a simplified version of this diagram in class and explain the difference
between the discontinuous reaction series and the continuous reaction series.
TASK 12 EXAMPLES OF BOWEN’S REACTION SERIES
In real magmas minerals form in the order of Bowen’s reaction series but the actual
minerals that develop depend on the original composition of the magma. This is
called the cooling history of an igneous rock.
Choose a specimen of gabbro, Shap granite and quartz feldspar porphyry. For each
give a description of its cooling history, after examining the mineralogy and texture
carefully under a lens or a microscope.
TASK 13 MAGMATIC DIFFERENTIATION
Gravity settling and fractional crystallisation can produce layered differentiated
igneous intrusions. Read IR 2 p 57 and IR 3 p 59.
Carry out this experiment carefully in the classroom. Fill a jam jar with golden
syrup to simulate a magma chamber full of melt. We can use a variety of materials
to simulate crystals of different sizes and densities forming in the magma chamber.
Drop a paper clip and a drawing pin into the magma chamber. Which reaches the
bottom of the magma chamber first? Why? Now repeat the experiment with a
grain of rice and a piece of pasta. Observe which item reaches the bottom first.
Record your results.
Write out two bivariate hypotheses linking size and density of crystals with settling
rate. Now clean up.
The crystals in these differentiated intrusions are often called cumulates because
the denser and larger crystals accumulate at the base of the magma chamber.
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Module exam GL4 June 2004
TASK 14 PALISADES SILL
Watch IR 17, is a powerpoint of differentiated igneous intrusions which will help
you understand the process of magmatic differentiation.
On a plain sheet of paper draw a large diagram showing the cross-section of the
Palisades Sill, New York, from IR 2 p 57 or IR 3 p 60. Using clear labels explain
the differentiation processes which cause layering of minerals within the sill. You
will need to add a scale. The presence of chilled margins is critical to the
understanding of the minerals and their position in the sill.
TASK 15 SOLID SOLUTION SERIES
Some minerals have crystal lattices which have spaces the right size for ions to
move into. This changes the chemistry of the mineral. According to the
availability of ions in the magma(or melt) and the temperature of the magma it is
possible to have a gradation of chemical composition in one mineral. This process
is called solid solution.
The two common minerals in which solid solution can occur are olivine and
plagioclase feldspar. These have continuous reaction series because the exchange
of ions can continue throughout the cooling of the melt until the magma crystallises
completely. We have met the continuous reaction series of plagioclase feldspar as
part of Bowen’s reaction series.
Use IR 18 to explain the process of solid solution.
TASK 16
OLIVINE AND PLAGIOCLASE
Olivine can have an iron-rich (fayalite)or a magnesium-rich composition
(forsterite), while plagioclase can have a sodium-rich (sodic) (albite)or calciumrich (calcic) (anorthite) composition.
1.
In class we will talk through olivine and plagioclase phase diagrams using the
terms liquidus and solidus to show how the composition of melts and crystals
can change as temperature falls.
2.
Explain the formation of zoned crystals and corona structures in crystals in
the light of the solid solution process.
TASK 17 BGS MAPS
Look at appropriate BGS maps and slides to see how igneous and volcanic features
are shown.
TASK 18
EXAM QUESTION PACK
Complete the Igneous Rocks EQP
Deadline……………………………………
Use this box for notes
ESTA GEOTREX The Geology Teachers Resource Exchange Contributor: Alison Quarterman Establishment: Greenhead College
Date:May 05
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Module exam GL4 June 2004
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