Today once again I am here to talk a little about what metamorphism is, its types, degrees and others. And I leave you this interesting topic below
Metamorphic rocks are formed from igneous, sedimentary rocks or even other metamorphic rocks. Therefore, all metamorphic rocks have a parent rock ie the rock from which they were formed.
It is a process that causes changes in the mineralogy, the texture and, often, the chemical composition of the rocks, and takes place when the rocks undergo a physical or chemical environment different from their initial formation. And those factors that cause metamorphism are heat, pressure and the presence of chemically active fluids.
Metamorphism usually progresses incrementally, from slight changes (low grade metamorphism) to notable changes (high grade metamorphism).
Slate.
The mud rock is transformed into scaly gray slate by low grade regional metamorphism. High pressure and low temperatures realign minerals found in clay, such as mica and chlorite, in flat layers
phillite.
Like the blackboard, the phillite is created by the moderate regional metamorphism of the rock of mud or slate. But the effect is more intense: the mica flakes are larger and more visible and develop a silky shine as a mirror.
schist.
Mid-grade metamorphism creates schist rock by making crystals of chlorite and mica in bands in the middle of others of quartz and feldspar. This grouping is called schistosity.
Gneiss.
Gneiss is formed with the highest degree of metamorphism. Extreme heat and pressure create a sparkling rock in which entirely new crystals form in dark and light wavy bands.
The metamorphosed rocks of mud rock and slate often carry wavy flat lines called foliation. Dark lines are created when the pressure flattens bands of laminar minerals, as it pits. Slate, phyllite, schist and gneiss have foliations like these. The metamorphosed rocks of limestone (marble), sandstone (quartzite), and coal (anthracite) do not have any of these foliations, and the glass interspersed grains do not show a specific pattern. This is called granular texture.
In the folds of gneiss, the separate bands of hornablenda and dark mica, and quartz and clear feldspar are visible. The crease is formed when rock-deformed by plate movements that are not as strong to alter the composition of the rock, as seen here in these folded bluffs of South Wales, UK.
