How are Crenulations formed?

Crenulations form when an early planar fabric is overprinted by a later planar fabric. Crenulations form by recrystallisation of mica minerals during metamorphism. Micaceous minerals form planar surfaces known as foliations perpendicular to the principal stress fields.

What is crenulation lineation in geology?

The crenulation lineation is the fabric element parallel to the tightly spaced hinges. Many schists exhibit this type of lineation. It generally is a good indication of superposed deformation.

What is mineral lineation?

Mineral lineations are sometimes defined by oriented single crystals of elongate minerals like hornblende or kyanite, but in other rocks the lineation is defined by elongate aggregates of grains, and the grains may be elongate or equant in shape.

What forms the lineation on the foliation plane?

In this case, the foliation plane carries a linear fabric called a lineation. This lineation is due to the stretching of grain aggregates, the re-orientation of elongated minerals (eg. amphibole, rutile), and the preferential growth of newly formed minerals.

Where is mylonite formed?

Mylonites form deep in the crust where temperature and pressure are high enough for the rocks to deform plastically (ductile deformation). Mylonites form in shear zones where rocks are deformed because of the very high strain rate.

What is a Crenulation used for?

Crenellation is a feature of defensive architecture, most typically found on the battlements of medieval castles. A battlement is a low, defensive parapet. The act of crenellation is the cutting of crenels into a previously solid and straight parapet wall.

What is the difference between Castellations and crenellations?

These gaps are termed “crenels” (also known as carnels, or embrasures), and a wall or building with them is called crenellated; alternative (older) terms are castellated and embattled. The act of adding crenels to a previously unbroken parapet is termed crenellation.

What are the types of lineation?

There are several types of lineations, intersection lineations, crenulation lineations, mineral lineations and stretching lineations being the most common. Lineation field measurements are recorded as map lines with a plunge angle and azimuth.

What is the difference between foliation and lineation?

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. hornblende) in this plane.

How is mylonite made?

Mylonite is a metamorphic rock formed by ductile deformation during intense shearing encountered during folding and faulting, a process termed cataclastic or dynamic metamorphism.

What is mylonite used for?

Mylonite is regularly used in the construction industry, road aggregate, landscaping, milestone, and architectural artifacts.