UT Arlington GEOL 2313 - Review Terms - Questions for Minerals and Rocks Second Midterm

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Review Terms/Questions for Minerals and Rocks Second Midterm 2008 Glen S. Mattioli Please plan to be able to give short definitions for any of the following terms. NB that only four to six will be on the exam. 1) Heat capacity 2) Normative mineralogy 3) Modal mineralogy 4) Eutectic point 5) Incompatible or compatible trace element 6) Calc-alkaline or tholeiite trend 7) Geothermal or geobaric gradient 8) Solidus 9) Liquidus 10) Freezing point depression 11) Component 12) Phase 13) Solid solution 14) Mole fraction 15) Degree of freedom (Gibbs Phase Rule) 16) Lever Rule and conservation of mass 17) Peritectic point 18) Tie line 19) Isotherm 20) Isopleth 21) Bulk composition 22) Saturation 23) Solubility 24) Silica activity 25) Alumina activity 26) Latent heat of crystallization or melting 27) Chemical equilibrium Below please find possible examples of short answer questions for the midterm exam. NB that on the exam you will be given two choices from which you will need to answer only one. 1) Equilibrium is an extremely important concept in natural science in general and petrology in particular. Define equilibrium and describe three states that a system may be in with respect to an equilibrium state. 2) Several different classification schemes for igneous rocks were discussed in class. List three different schemes and outline the characteristics of each. 3) Igneous rocks are broadly divided into intrusive and extrusive groups. What are the relative volumes of these groups for various major tectonic settings?4) Chemistry of igneous rocks and their constituent minerals is an essential part of developing a petrologic model for their formation and evolution. How is bulk chemistry measured in igneous rocks? What is the standard way in which the chemical variation is reported? Below please find possible examples of essay questions for the midterm exam. NB that on the exam you will be given three choices from which you will need to answer only two. 1) When magma reaches the surface or near surface environment on Earth it will exchange heat with its surroundings. What are the four principal mechanisms by which this heat exchange occurs? How are they different? What are the important parameters that control the heat flux from the magma body or lava to its surroundings? 2) Discuss the equilibrium crystallization history of a liquid whose bulk composition and initial temperature in a binary system are defined. Use the Phase and Lever Rules to describe the system's characteristics at different points. Draw a temperature-time diagram for this cooling history. What thermodynamic parameters control the cooling rate? 3) Assume that phenocrysts of zoned plagioclase, with variable edge An-contents, are similar in composition to others found within an aphanitic, mesocratic groundmass composed of fine-grained plagioclase, clinopyroxene, trace olivine, minor iron-oxides, and brown glass. Draw an appropriate binary phase diagram for the feldspar system and outline a crystallization history to account for the plagioclase compositional variation. Based on the other observations (mineralogy and texture) suggest a possible parental magma composition and mode of occurrence.SOME KEYS TO GETTING FULL CREDIT Definitions/Short Answer - Please give examples where necessary (5 points each): 1) Phase 2) Incompatible trace element I would expect a one to two sentence definition or explanation for these terms. Normally you would receive full credit only if you a complete and correct answer. For example, “A phase is a physically and chemically distinct entity that is mechanically separable from other phases. Each phase within a system has a boundary with other phases. The composition of all phases within a system is defined by specific chemical components.” SHORT ANSWER QUESTIONS - CHOOSE ONLY ONE OF TWO (each is worth 20 pts.) Please write in complete sentences and give examples as necessary. Label all drawings and figures clearly. 1) Equilibrium is an extremely important concept in natural science in general and petrology in particular. Outline at least two definitions/concepts of equilibrium and describe three states that a system may be in with respect to an equilibrium state. Here I would expect a much more complete answer. Since I request that you give two definitions, each would be worth 10 pts. Then I would further divide the credit based on the level of detail and correctness of the answer. One definition would be ΔG = 0 and what this implies, and the three states are: unstable, metastable, and stable. ESSAY QUESTIONS – CHOOSE ONLY TWO OF THREE (each is worth 30 pts.): Please write in complete sentences and give examples as necessary. Label all drawings and figures clearly. You may use the back of the page (only 1 page) of each question to continue your answer. 1) When magma reaches the surface or near surface environment on Earth it will exchange heat with its surroundings. What are the four principal mechanisms by which this heat exchange occurs? How are they different? What are the important parameters that control the heat flux from the magma body or lava to its surroundings? Here you really need to get all the detail associated with the question. Make sure you address each point in turn. You would need to list the 4 mechanisms and describe each in detail. Examples of each mechanism related to the problem at hand are essential. Then you would need to describe or define the relationship for heat flux and explain all the terms in the


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UT Arlington GEOL 2313 - Review Terms - Questions for Minerals and Rocks Second Midterm

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