Metamorphism and metamorphic Rocks Prof Dr Ziad Salem

Metamorphism and metamorphic Rocks Prof. Dr. Ziad Salem Abu-Hamatteh Faculty of Engineering Technology Al-Balqa’ Applied University

Metamorphism and metamorphic Rocks Metamorphism: all changes (textural/mineralogical) that take place on a pre-existing rock(I, S, M) in response to new conditions (P/T) imposed on the rock which are different from those under which the rocks have originally been formed. Changes take place in the solid state

Original Unmetamorphosed rock Nucleation of new minerals in response to changes in T or P or both A B Ions migrate either by solid state diffusion or Different stages of Intergranular fluids mineral growth C involve both textural and mineralogical changes Si. O 2 + Ca. CO 3 Ca. Si. O 3 + CO 2 Best, 1982

Deformed metamorphic rocks

Types or Envs. of metamorphism • Contact (thermal) metamorphism = around magmas • Regional metamorphism = along subduction zones in areas of mountain building. Rocks in these setting are subjected to both increase in T and to directed pressures.

Contact metamorphism

Subduction zone and regional metamorphism

Agents of metamorphism • Heat = thermal energy geothermal gradient • Pressure increases at a rate of about 250300 bars/km of depth. • Chemical active hot fluids (H 2 O, CO 2 are the most common) moving within the rocks are capable of dissolving rocks and precipitating others at other places

Confining pressure=analogous to hydrostatic pressure

Differential stresses = directed pressures

• Foliated rocks • = regional • Metamorphic • rocks Textures

Common metamorphic rocks

Slate

Phyllite http: //geology. about. com/library/bl/images/blphyllite. htm

Garnet Schist

Garnet schist

Mica schist

Gneiss

Banded gneiss

Folded metamorphic rocks