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Petrology

Petrology. The study of the properties of rocks and the processes behind their formation Recognition and description of rocks Interpretation of their origin and history. Instructor. Michael F. Sheridan email: mfs@geology.buffalo.edu Homepage: http://www.eng.buffalo.edu/~mfs

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Petrology

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  1. Petrology • The study of the properties of rocks and the processes behind their formation • Recognition and description of rocks • Interpretation of their origin and history

  2. Instructor • Michael F. Sheridan • email: • mfs@geology.buffalo.edu • Homepage: • http://www.eng.buffalo.edu/~mfs • Office hours: • We & Th 1:00-2:00 PM

  3. Fundamentals • Classification • Changing States (Equilibrium) • Plate Tectonics & Petrology • Thermodynamics • Kinetics

  4. Magmatic Rock Bodies • Study of rocks in hand sample • Descriptive Petrochemistry • Origin and evolution of magmas • Interpretative Petrochemistry

  5. Study of rocks in hand sample • Fabric • Rock forming minerals • Classification

  6. Fabric • Phaneritic • Aphanitic • Glassy • Clastic

  7. Sequence of mineral formation • Degree of perfection of form • Inclusion within other minerals • Chemical zonation • Signs of deformation • Secondary growth • Alteration to secondary minerals

  8. Rock forming minerals • Feldspars • Quartz • Pyroxenes • Olivines • Amphiboles • Micas • Feldspathoids

  9. Classification • Leucocratic • Felsic • Silicic • Mafic • Ultramafic

  10. Rock Suites • Mafic and ultramafic • Calc-alkaline • Highly alkaline

  11. Descriptive Petrochemistry • Chemical analyses • Major elements • Trace elements • Relation of chemistry to mineralogy

  12. Chemical classification • Silica concentration • Acid >66% • Intermediate 52-66% • Basic 45-52% • Ultrabasic <45%

  13. Silica saturation • Oversaturated • compatible with quartz • Saturated • Neither undersaturated minerals nor quartz • Undersaturated • undersaturated minerals

  14. Alkali/Aluminum saturation • Relative to feldspar composition • NaAlSi3O8 • Peralkaline • Peraluminous • Calc-alkaline

  15. CIPW norm • Definition • How calculated • Use in classification

  16. Chemistry of rocks • Major elements • Trace elements • CIPW norm

  17. From Mineral Composition to Rock Composition • Determine the minerals present • estimate their abundance • Calculate the rock composition using proper weightings

  18. Interpretative Petrochemistry • Models of crystallization • Concepts of magma movement • Secondary alteration

  19. Ultramafic rock bodies • Petrography of gabbroic and ultramafic rocks • Nature of Plutons • Oceanic subalkaline basaltic to ultramafic associations • Ophiolites

  20. Petrography of gabbroic and ultramafic rocks • General • phaneritic grain size • may be nearly monomineralic • Pyroxene • Olivine • Plagioclase • Fabric • Slow sequential growth • Hypidiomorphic granular

  21. Petrography of gabbroic and ultramafic rocks • Classification • Alteration • deuteric and hydrothermal alteration • Serpentine • Secondary iron oxide • brucite & talc

  22. Nature of Gabbroic Plutons • Dikes, sills, and plugs • Layered intrusions • Slow shallow cooling of basaltic magma

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