Lectures on Rheology of Earth Materials Fundamentals 土材料流變學(xué)講座

1、Lectures on Rheology of Earth MaterialsFundamentals and frontiers in the study of deformation of minerals and rocks(at Tohoku University)Shun-ichiro KaratoYale UniversityDepartment of Geology & GeophysicsNew Haven, CT, U.S.A.June 25-27, 2003Lecture Outline1. Why rheology?2. General backgrounddefects

2、 and plastic deformationthermodynamics3. Some fundamentals of creep3-1. Diffusion and diffusion creep3-2. Dislocations, slip systems, and dislocationcreep3-3. Deformation mechanism maps3-4. Effects of phase transformations3-5. Effects of pressure, water4. Physical processes controlling the grain siz

3、e4-1. Grain-growth4-2. Dynamic recrystallization4-3. Nucleation-growth 5. Some applications5-1. Lithosphere-asthenosphere5-2. Rheology subducting slabs5-3. Some unresolved problems時(shí)間依存性性質(zhì)扱実験結(jié)果直接地球応用。実験室結(jié)果地球応用物理的則確立必要。例：流動(dòng)則、結(jié)晶粒徑（相転移）要點(diǎn)。則要點(diǎn)。的性質(zhì)溫度、水、相転移、結(jié)晶粒徑地球進(jìn)化、密接関係。（密度弾性的性質(zhì)違。）Why rheology?Rheology co

4、ntrols mantle convection.Mixing of geochemical reservoirsRheology has strong influence on the way in which seismic wave propagation is affected by mantle convection.anelasticity, anisotropyWhat causes velocity heterogeneity: thermal or chemical origin (or both) ?Much of the velocity heterogeneity in

5、 the upper mantle has chemical origin (ocean vs. continent). To what extent is the deep mantle chemically heterogeneous?In regions where there is chemical heterogeneity, what is the cause of heterogeneity (which elements or which minerals)?Ritsema et al. (1999)Models to explain geophysical and geoch

6、emical observations (Tackley, 2000) Upper mantleTransition zoneTrampert and van Heijst (2002)Pattern of anisotropy is very different between the upper mantle and the transition zone. What does it tell us?What do we want to know?How does rheology control convection pattern?What is the rheological str

7、atification in Earth?How can we infer flow pattern from seismological observations?How does rheology affect mixing?Where are geochemical reservoirs and how have they survived (or not survived)?Why plate tectonics on Earth and not on Venus?What are the mechanisms of localization of deformation? How h

8、ave continents survived for billions of years?Is continental lithosphere ”dry” or “wet”?Frontiers in the study of deformationof minerals and rocksExtreme conditionsHigh-pressure(whole Earth dynamics)Large strain(anisotropy, grain-size evolution, strain partitioning)Small strain(seismic tomography-an

9、elasticitypost-glacial rebound)Complexitiesdeformation chemical reaction(s) metamorphism, phase transformations, partial melting, hydrogen redistribution-deformation microstructural evolutioninstability, localization: “plate” formation, deep earthquakesSome fundamentals of mineral and rock rheologyT

10、-P dependence of plastic deformationStress, grain-size dependenceDependence on chemical environmentEffects of phase transformationsElastic deformationPlastic deformation: involves atomic jumpsthermally activated processesprobability T-dependence time-dependenceTemperature dependence of elastic const

11、antand viscosity: ductile strength (viscosity) is highlysensitive to TPressure dependence of elastic constantand viscosity: ductile strength (viscosity) is highlysensitive to PBasic physics of plastic deformationDefects and plastic deformationthermo-chemical equilibrialaw of mass actionfugacityThermally activated processesorigin of t-T dependenceBoltzmann statisticsPoint defectsEffects of oxygen fugacity on defect concentrationThe Krger-Vink Diagram f