Regional metamorphosim in petrology

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At Periyar University Salem

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Keeranur Pudukkottai tamilnadu India
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1. IGNEOUS AND METAMORPOIC PETROLOGY REGINOAL METAMORPHISM By: THOMAS CHINNAPPAN .A , M.SC.APPLIED GEOLOGY, PERIYAR UNIVERSITY, SALEM.

2. Definition of regional metamorphism Metamorphism affecting rock over an extensive area as a result of the large scale action of heat and pressure.

3. regional metamorphism Regional metamorphism is occurrence over broad areas of the crust . The form a deformation during an orogenic events of mountain belts The eroded to expose the metamorphic rock Usually regional metamorphism occur when the rock buried deep in crust The associated with Convergent plate boundaries

4. Regional metamorphism found Most regional metamorphism take place within continental crust Metamorphosed at depth. Potential for metamorphism is greater root of mountain Young sedimentary rock to greater depth .

5. TYPES OF REGIONAL METAMORPHISM OROGENIC METAMORPHISM BURIAL METAMORPHISM OCEAN FIOOR METAMORPHISM

6. Orogenic metamorphism orogenic metamorphism is the type of metamorphism associated with convergent boundaries. Dynamo thermal –combined elevated geothermal and deformation Foliation- rock are a characteristic product Island arch ,active continental ,margin continental ,collision zone. They are located in alps of north Appalachians mountain of eastern north America .

7. Burial metamorphism The term coined by coombs [1961] Southland syncline in new Zealand ;thick pile [>10km] mesozoic volcaniclastics. Mild deformation ,no igneous intrusion discovered Fine grained ,high temperature phases ,glassy ash. Metamorphic effect attributed to increased temperature and pressure due to burial Diagenesis grades into the formation of zeolites,laumontite , ect …… Burial metamorphism low grade . The occurs in sedimentary basin due to burial by successive layer . Temperature low grade upto ~300 degree c .

8. Ocean floor metamorphism Ocean floor metamorphism is caused by circulation hot water in hydration of water free magmatic minerals and newly formed oceanic crust at mid-oceanic ridges . temperature range (200-700 degree c ). Pressure is low (< 0.5pa). A wide range of temperature at low temperature. Affects the oceanic crust at ridge spreading centre . Wide range of temperature at relatively low pressure. Metamorphic rock considerable metasomatic alteration, Loss of ca and si and mg. Seawater penetrates down fracture system .

9. Ocean –ridge metamorphism take place at mid –oceanic in response to sea floor spreading . The plate tectonic setting is characterized by divergent boundaries. Resulting of this metamorphic rock include green stone and amphibolites . Low grade and medium grade metamorphism Convert of greenstone or amphibolites H2O in the rock Hydrothermal circulation of fluids.

10. Period of regional metamorphism : Archean to Cenozoic time. Some 252 million years ago. Eg …. Circum pacific belt ,the alps ,Greek Cyclades . EXAMPLE OF REGIONAL METAMORPHISM ROCK: Slate Schist gneiss