What is a foliation plane?

What is a foliation plane?

Foliation, planar arrangement of structural or textural features in any rock type but particularly that resulting from the alignment of constituent mineral grains of a metamorphic rock of the regional variety along straight or wavy planes.

How do you describe foliation?

Foliation in geology refers to repetitive layering in metamorphic rocks. Each layer can be as thin as a sheet of paper, or over a meter in thickness. The word comes from the Latin folium, meaning “leaf”, and refers to the sheet-like planar structure.

What are the 3 types of foliation?

There are three types of foliated rocks: slate, schist, and gneiss. Each type varies based on the size of the mineral grain and how foliation is characterized.

How is foliation formed?

Foliated Metamorphic Rocks: Foliation forms when pressure squeezes the flat or elongate minerals within a rock so they become aligned. These rocks develop a platy or sheet-like structure that reflects the direction that pressure was applied.

What happens during foliation?

Foliation occurs in metamorphism when pressure is high enough in one orientation so as to flatten the parent rock material or to induce the platy minerals to crystallize in an orientation perpendicular to the direction of the highest pressure. Not all metamorphic rocks have foliation.

What type of stress would cause foliation?

Most foliation is caused by the preferred orientation of phylosilicates, like clay minerals, micas, and chlorite. Preferred orientation develops as a result of non-hydrostatic or differential stress acting on the rock (also called deviatoric stress).

Does heat cause foliation?

Igneous rocks such as granite and basalt crystallize as they cool from a molten state, called magma. Metamorphic rocks, including gneiss and marble, change when extreme heat and pressure cause mineral changes through recrystallization. Many metamorphic rocks appear to be layered, an effect called foliation.

What is lineation and foliation?

Foliation is the result of the parallel arrangement of (micas, etc.) in a plane perpendicular to the maximum principal applied stress. A lineation is caused by a similar growth of elongate minerals (eg. Slate, schist, and gneiss are three common foliated metamorphic rocks.

What causes the foliation to form?

Foliation forms when pressure squeezes the flat or elongate minerals within a rock so they become aligned. These rocks develop a platy or sheet-like structure that reflects the direction that pressure was applied.

Does confining stress cause foliation?

Cause of Foliation All rocks are under pressure as a result of burial. This confining pressure increases in proportion to the depth of burial. This means that differential stress related to different pressure in different directions is required to form foliated metamorphic rocks.

What do you mean by foliation in geology?

Foliation • Foliation in geology refers to repetitive layering in metamorphic rocks. Each layer may be as thin as a sheet of paper, or over a meter in thickness.

What does foliation tell us about a thrust fault?

Foliation in areas of shearing, and within the plane of thrust faults, can provide information on the transport direction or sense of movement on the thrust or shear. Generally, the acute intersection angle shows the direction of transport.

How is the foliation plane used in geotechnical engineering?

In geotechnical engineering a foliation plane may form a discontinuity that may have a large influence on the mechanical behavior (strength, deformation, etc.) of rock masses in, for example, tunnel, foundation, or slope construction.

How are lineations related to the foliation plane?

Lineations due to ductile deformation lay on foliation planes and are, therefore, as penetrative as foliations. A single deformation may produce several sets of lineations with different orientations within a given foliation plane. Lineations are referred to as L -elements of the rock fabric.