7.1 Metamorphism

Rocks that have undergone metamorphism

the change undergone by an existing rock (ign, sed, or met) in the solid state, to another rock

During metamorphism, the rock must remain essentially in this state

Metamorphic settings

driven by a rise in temperature within the host rock

chemical alterations from hot, ion-rich water

occurs during mountain building

What type of metamorphic settings produces the greatest volume of metamorphic rocks

results from increasing temperature and/or pressure conditions over time

results from decreasing temperature and/or pressure so that lower temperature/pressure mineral assemblages develop that overprint earlier peak temperature/pressure mineral assemblages

they serve as catalysts in driving retrograde metamorphic reactions as without them, retrograde metamorphic conditions are difficult to attain because previously occurring prograde metamorphism has already depleted the rock in volatile components

The most important agent of metamorphism

2 sources of heat

An agent of metamorphism, it increases with depth

2 types of pressure

it applies forces equally in all directions

Rocks may also be subjected in this type of pressure which is unequal in different directions

Agent of metamorphism, mainly water with other volatile components. They enhance migration of ions, and aid in recrystallization of existing minerals

Sources of fluids

the parent rock of metamorphic rocks, the original, unmetamorphosed rock from which a given metamorphic rock is formed

2 main classification of metamorphic rocks

Protolith of Slate

Protolith of Schist

Protolith of Gneiss

Protolith of Quartzite

Protolith of Marble

Protolith of Anthracite coal

Types of metamorphism

Occurs due to a rise in temperature when magma invades a host rock

It is a zone of alteration that forms in the rock surrounding the magma during contact metamorphism

Contact metamorphism takes place in low pressure and at these depths

type of metamorphic rocks produced by contact metamorphism

Chemical alteration at high temperatures and moderate pressures by hot-ion rich fluids that circulate through fissures and cracks. Common in basaltic rocks

This is where hydrothermal metamorphism commonly occur

Takes place at considerable depths over an extensive area under high pressure and is associated with the process of mountain building

The depth where regional metamorphism takes place

Associated with very thick sedimentary strata. Required depth varies from one location to another depending on the prevailing geothermal gradient.

Occurs at depth and high temperatures. Pre-existing minerals deform by ductile flow. “Slickensides”

Occurs when high speed projectiles called meteorites strike Earth’s surface

Products of impact metamorphism