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H.W. #3 + Read Solar Nebula Theory Study Guide for exam 2 Study Area for lab has practice exam All missed labs must be made up before lab exam All missed homework must be made up before lecture exam 2
Practice Lab Exam Lab Samples Study Area Felmley Hall 203
Definitions Metamorphism – mineralogical, chemical, and physical changes that occur in solid rocks. Occurs at depths greater than that of sediments and sedimentary rocks Solid state recrystallization – changes that occur without the rock melting (rocks that melt are igneous).
Surface 5 km 30 km 200 o C 600 o C Sedimentary Metamorphic Magma 15 o C
Factors influencing Metamorphism Temperature Pressure Pore Fluid Time
Factors influencing Metamorphism Temperature below about 200 o C, most minerals are stable (little or no metamorphism) above 200 o C, reaction rate increases as temperature increases, new minerals begin to form above 600 o C, some minerals begin to melt (transition to igneous rocks)
Factors influencing Metamorphism Pressure as pressure increases, pore spaces reduced and density increases, pore fluids are expelled Differential stress pressure is greater in one direction than in another
Differential Stress Foliation – a metamorphic rock texture due to alignment of minerals as a result of differential stress Slaty cleavage – foliation that develops at low temperature and pressure (metamorphosed shale)
Foliation In this schist, viewed between crossed polarisers, the parallel mica flakes show up in bright colors, and large rounded garnet crystals appear black. Field of view 6 mm, polarising filters.
Factors influencing Metamorphism Pore fluids (water and carbon dioxide) as pressure increases, pore fluids are expelled Pore fluids increase the rate of metamorphic reactions by: storing ions involved in reactions moving ions from one place to another
Types of Metamorphism Burial Metamorphism most common type, occurs where crust is greater than 5 km thick Relatively low temp. and pres. at shallow depths through High Temp. and Press at great depths Maximum stress vertical, foliation parallel to ground surface
Types of Metamorphism Regional Metamorphism associated with convergent plate margins folding and faulting increase thickness of the crust occurs over a range of temperatures and pressures low grade to high grade metamorphism