Geology > QUESTIONS & ANSWERS > GEOL 3041 Answers for Chapter 3: Textures of Igneous Rocks. 100% Pass Rate (All)

GEOL 3041 Answers for Chapter 3: Textures of Igneous Rocks. 100% Pass Rate

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GEOL 3041 Answers for Chapter 3: Textures of Igneous Rocks. 1. Other than the externally-imposed cooling rate, what are the three principal rates that govern rock texture? 2. What is typically the d... etermining (limiting) rate when large crystals form? Explain. 3. What is the determining rate when dendritic crystallization takes place? Explain. 4. What is the distinction between primary textures and secondary textures? 5. Explain how porphyritic texture is most likely to develop. 6. Pyroxene can be replaced by hornblende, biotite, or chlorite as a pluton cools. Hornblende can be replaced by biotite or chlorite. Biotite can be replaced by chlorite. What common feature of these sequences most easily explains them? Hint: look up the formulas of each mineral. 7. Quartz commonly exhibits interstitial texture with respect to feldspars. What does this imply in terms of crystallization sequence? Why? 8. What is “normal” zoning in a plagioclase? Give two reasons why plagioclase typically exhibits zoning in thin section whereas olivine does not. 9. What is granophyric texture and how does it form? 10. How does trachytic texture differ from pilotaxitic texture? 11. What is cumulate texture and how does it form? 12. What is the usual result of Ostwald ripening? 13. How do displacive polymorphic transformations differ from reconstructive ones? Which is more likely to preserve the high-temperature polymorph in low-temperature rocks? Why? Are vesicles more plentiful in the upper portions or the lower portions of basaltic lava flows? Why? [Show More]

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