Research on Metamorphism
Introduction
Metamorphism is defined as the mineralogical, chemical and structural adjustments in solid rocks to physical and chemical conditions which have been imposed due to changes in pressure and temperature or both. Metamorphism occurs below the surface zones of weathering and cementation. Conditions of metamorphism differ from the conditions under which the rocks in question were originally formed. Metamorphism produced as a result of the progressive increase in temperature and pressure, i.e. by burial of a rock within the earth, is termed prograde metamorphism and in general terms is characterized by dehydration reactions, which release water.
Agents of Metamorphism
1) Heat a) frictional sliding of plates b) radioactivity c) gravitational compression
2) Pressure a) burial (lithostatic) b) directed pressure due to tectonism
3) Chemically Active Fluids a) Water - circulates in response to heat generated by cooling magmas. Exchanges ions between the solution and the rock through which it is traveling.
Types of Metamorphism
Dynamic metamorphism - Metamorphism along faults zones in response to pressure. Involves a brittle deformation of the rock during which it is ground into fine particles. Heat and chemical fluids are less important. Most important rock is mylonite a very distinctive lineated rock.
Contact metamorphism - Alteration of rocks at or near the contact of a cooling pluton. Most important agents of metamorphism are heat and circulating fluids. Temperatures 300-800 degrees C. Produces a series of zones characterized by the presence of one or more diagnostic minerals.
Regional metamorphism - Occurs over a very large area in response to increased temperature and pressure. Circulating fluids are unimportant due to the great depth of regional metamorphism. Pressure seals pore space in the rocks and fluids can't circulate. Generally, regional metamorphism occurs in tectonically active areas (i.e. plate margins).
Metamorphism is defined as the mineralogical, chemical and structural adjustments in solid rocks to physical and chemical conditions which have been imposed due to changes in pressure and temperature or both. Metamorphism occurs below the surface zones of weathering and cementation. Conditions of metamorphism differ from the conditions under which the rocks in question were originally formed. Metamorphism produced as a result of the progressive increase in temperature and pressure, i.e. by burial of a rock within the earth, is termed prograde metamorphism and in general terms is characterized by dehydration reactions, which release water.
Agents of Metamorphism
1) Heat a) frictional sliding of plates b) radioactivity c) gravitational compression
2) Pressure a) burial (lithostatic) b) directed pressure due to tectonism
3) Chemically Active Fluids a) Water - circulates in response to heat generated by cooling magmas. Exchanges ions between the solution and the rock through which it is traveling.
Types of Metamorphism
Dynamic metamorphism - Metamorphism along faults zones in response to pressure. Involves a brittle deformation of the rock during which it is ground into fine particles. Heat and chemical fluids are less important. Most important rock is mylonite a very distinctive lineated rock.
Contact metamorphism - Alteration of rocks at or near the contact of a cooling pluton. Most important agents of metamorphism are heat and circulating fluids. Temperatures 300-800 degrees C. Produces a series of zones characterized by the presence of one or more diagnostic minerals.
Regional metamorphism - Occurs over a very large area in response to increased temperature and pressure. Circulating fluids are unimportant due to the great depth of regional metamorphism. Pressure seals pore space in the rocks and fluids can't circulate. Generally, regional metamorphism occurs in tectonically active areas (i.e. plate margins).