Igneous and Metamorphic Petrology

GEOL-4711  Spring 2014

Review for 2^nd Lecture Test

 

 

Thermodynamics (Chapters 5 and 6)

1) Be able to give mineral examples and draw phase diagrams for each of the following: binary solid solution, binary eutectic, binary exsolution, and binary peritectic systems.

2) Describe and draw the Di-An-Fo Ternary System.  Be able to plot compositions on the diagrams and predict melting or crystallization histories.  Why is this system so important?

 

 

Magma Generation and Diversification (Chapter 10)

1) Define and describe the important characteristics of ultramafic xenoliths and ophiolites.  How do these samples compare with dredge samples from oceanic transform faults? Why and how are these terrestrial samples used in combination with seismic and meteorite data to predict the composition of the mantle?  Describe the proposed composition of the mantle. 

2) List and describe the three major causes of mantle melting.  Along which tectonic boundaries are each of these important?

3) What are the important characteristics of primary magma?  What is a eutectic melt?  Why are there variations in the composition of eutectic melts if they form at invariant points?

4) Explain how alkaline and subalkaline parental basalt magma can be derived from a homogeneous mantle?  List the geochemical evidence for the origin of alkaline magma by lower degrees of partial melting.

5) Describe the heterogeneous model for mantle compositions and magma generation. 

6) Describe the geochemical characteristics of the alkaline magma series.  List and describe the rock types and tectonic associations that characterize alkaline magma.  Describe the most widely accepted model for production of alkaline magma.  How and why is the Na₂O+K₂O/SiO₂ diagram used to differentiate alkaline and subalkaline magmatic series?

7) Describe the geochemical characteristics of the tholeiitic magma series.  Be able to draw and label tholeiitic and calc-alkaline series on an AFM Diagram.  Why is this diagram used to differentiate these series?  List and describe the rock types and tectonic associations that characterize tholeiitic magma.  Describe the most widely accepted model for production of tholeiitic magma.

8) Describe the geochemical characteristics of the calc-alkaline magma series.  List and describe the rock types and tectonic associations that characterize calc-alkaline magma.  Describe the most widely accepted model for production of calc-alkaline magma.

9) Describe how partial melting and fractionation (melt separation) can produce magmatic compositions that are different than source rock compositions.  List the factors that can change magmatic compositions during melt separation.

10) List and describe the three major types of crystal fractionation.  Explain how Stokes Law can be used to determine which minerals will fractionate.  Why is crystal fractionation more important in mafic than felsic magma?

11) Define the other types of magmatic differentiation: volatile transfer, liquid immiscibility, magma mixing, assimilation, and compositional layering.  Describe how each of these can change magmatic composition.

12) Define the following: lherzolite, harzburgite, wehrlite, pyrolite, dunite, pyroxenite, MORB, eutectic melt, and cumulates.

Tholeiitic Magma (Chapter 13)

1) List and describe the important petrographic and mineralogic characteristics of tholeiitic magma.  Describe the general abundance and tectonic/geographic distribution of these magmas. 

2) List and describe the following volcanic landforms and structures that are commonly associated with tholeiitic magmatism: lava flows, shield volcanoes, plateau flood basalts, mid-oceanic ridges and rises, back-arc basins, and layered mafic intrusions.  Give geographic examples of each of these.

3) Describe the most widely-accepted theory for the origin of tholeiitic magma. 

4) Compare and contrast mid-oceanic ridges and rises.  In these comparisons include a discussion of spreading rates, elevation changes, geographic examples, and geologic structures.  Why do transform faults form in these areas and why do they result in both lateral and vertical offset?

5) List and describe the four major layers that form typical oceanic crust.  Make a simple sketch showing these layers and labeling the average thickness and composition of each layer.

6) Describe the important petrographic and geochemical characteristics of mid-oceanic ridge basalt (MORB).  Why are most MORBs believed to not be primary melts?  Describe how both N-and P-MORBs reportedly form. 

 

Calc-Alkaline Volcanism and Plutonism (Chapter 17)

1) List and describe the important petrographic and mineralogic characteristics of calc-alkaline magma.  Describe the general abundance and tectonic/geographic distribution of these magmas. 

2) List and describe the following volcanic landforms and structures that are commonly associated with calc-alkaline magmatism: stratovolcanoes, island arcs, and back-arc basins.  Define and describe the following products of calc-alkaline volcanism: lava flows, pyroclastics, air-fall tuffs, ash-flow tuffs, and lahars.

3) Define, compare and contrast S- and I-type granites.  List the distinguishing characteristics for each.  When do large intrusions commonly form relative to subduction zone development?

4) Compare and contrast hyper- and subsolvus granites.  List the important geochemical and mineralogic characteristics of each.  Be able to draw the albite-orthoclase phase diagram for each. 

5) List and describe the important characteristics of active continental margin volcanism.  Describe the magmatic compositions that are commonly associated with these tectonic locations.

6) Describe the proposed origin of active continental margin volcanism.

7) Define the following terms: Nuee Ardente, Benioff Zone, accretionary wedge, batholiths, stock, and large ion lithophiles (LIL).

 

Alkaline Magmatism (Chapter 19)

1) List and describe the important petrographic and mineralogic characteristics of alkaline magma.  List and describe the common rock types associated with alkaline magma? 

2) Describe the general abundance and tectonic/geographic distribution of alkaline magma.  Give geographic examples of each of these.

3) List and describe the evidence that indicates a deep mantle origin for alkaline magma.  Why are they believed to form by low degrees of partial melting of the mantle?  Describe the evidence that indicates measurable crystal fractionation occurs in alkaline magma.

4) Define the following terms: Hawaiite, mugearite, trachyte, and basanite.