Presentation on theme: "Introduction to Metamorphic Petrology"— Presentation transcript:
1Introduction to Metamorphic Petrology Recommended Textbook: J.D. Winter (2001) An Introduction to Igneous and Metamorphic Petrology: Prentice Hall Pub.
2Scope of Metamorphic petrology Metamorphic petrology is the study of the subsolidus changes that a rock undergoes when exposed to physicochemical conditions different from those prevailing near the surface of the Earth.Metamorphism produces changes in mineral assemblages and textures that reflect re-equilibration of the rock to the new physicochemical conditions, i.e., minimization of the energy of the system.Metamorphism is commonly isochemical (except for volatile components, e.g., H2O, CO2). Where the system is open, the process is referred to as metasomatism.
13Orogenic Metamorphism and differential stress Foliation (or Cleavage) and Lineations1s1 > s2 = s3 foliation and no lineations1 = s2 > s3 lineation and no foliations1 > s2 > s3 both foliation and lineation
14Onset of Orogenic Metamorphism ShaleSlateBeddingCleavageBedding
33Facies SeriesThe high P/T series, for example, typically occurs in subduction zones where “normal” isotherms are depressed by the subduction of cool lithosphere faster than it can equilibrate thermallyThe facies sequence here is (zeolite facies) - (prehnite- pumpellyite facies) - blueschist facies - eclogite facies.The medium P/T series is characteristic of common orogenic belts (Barrovian type)The sequence is (zeolite facies) - (prehnite-pumpellyite facies) - greenschist facies -amphibolite facies - (granulite facies)Crustal melting under water-saturated conditions occurs in the upper amphibolite facies (the solidus is indicated in Fig. 25-2)The granulite facies, therefore, occurs only in water-deficient rocks, either dehydrated lower crust, or areas with high XCO2 in the fluidThe low P/T series is characteristic of high-heat-flow orogenic belts (Buchan or Ryoke-Abukuma type), rift areas, or contact metamorphismThe sequence of facies may be a low-pressure version of the medium P/T series described above (but with cordierite and/or andalusite), or the sequence (zeolite facies) - albite-epidote hornfels facies - hornblende hornfels facies - pyroxene hornfels faciesSanidinite facies rocks are rare, requiring the transport of great heat to shallow levels