What does biotite break down into?

They react to form biotite + quartz + water. It finally breaks down to form granulitic rock composed of pyroxene + K-feldspars. Biotite is usually altered to clay minerals montmorillonite and vermiculite. Biotite and muscovite are the two most common mica minerals that often occur together in Al-rich igneous rock.

What is a Univariant reaction?

Univariant Reactions. For a given rock composition, a univariant reaction is one that plots as a line or curve on a pressure-temperature diagram.

What causes prograde metamorphic reactions?

Prograde and retrograde Prograde metamorphism involves the change of mineral assemblages (paragenesis) with increasing temperature and (usually) pressure conditions. These are solid state dehydration reactions, and involve the loss of volatiles such as water or carbon dioxide.

What is metamorphic mineral reaction?

A metamorphic reaction is a chemical reaction that takes place during the geological process of metamorphism wherein one assemblage of minerals is transformed into a second assemblage which is stable under the new temperature/pressure conditions resulting in the final stable state of the observed metamorphic rock.

Does biotite react with acid?

Biotite dissolves in both acid and alkaline aqueous solutions, with the highest dissolution rates at low pH. However, biotite dissolution is highly anisotropic with crystal edge surfaces (h k0) reacting 45 to 132 times faster than basal surfaces (001).

How is chlorite formed?

Chlorite forms by the alteration of mafic minerals such as pyroxenes, amphiboles, biotite, staurolite, cordierite, garnet, and chloritoid. Chlorite can also occur as a result of hydrothermal alteration of any rock type, where recrystallization of clay minerals or alteration of mafic minerals produce chlorite.

What is Univariant system?

Definition of univariant : having one degree of freedom —used of a physical-chemical system — compare bivariant, phase rule.

What is the difference between prograde and retrograde metamorphism?

In general, the changes in mineral assemblage and mineral composition that occur during burial and heating are referred to as prograde metamorphism, whereas those that occur during uplift and cooling of a rock represent retrograde metamorphism.

What is layered or banded appearance?

Foliated metamorphic rocks such as gneiss, phyllite, schist and slate have a layered or banded appearance that is produced by exposure to heat and directed pressure. Non-foliated metamorphic rocks such as hornfels, marble, quartzite and novaculite do not have a layered or banded appearance.

Does biotite mica react to acid?

Does phyllite react with acid?

A low grade phyllite can have a certain volume of calcite and still be a phyllite as long as the major components are quartz, mica and chlorite originally derived from mudstone and siltstone. The reaction to acid (usually HCl) can be quite strong even with low percentages of calcite.