Phyllite - Kilmacrenan
Collection:
Click the microscope button to view a thin section for this sample.
Microscope
Click the microscope button to view a thin section for this sample.
Microscope

Fact sheet

Phyllite - Kilmacrenan

This sample of fine grained low grade metamorphic rock comes from SW of Doon Rock, an inland promontory fort that rises above the surrounding countryside, a short distance north of the village of Kilmacrennan in County Donegal, Ireland. The rock was deposited as a finely banded siltstone-mudstone in the late Proterozoic period, before being subject to regional metamorphism. It now forms part of the Dalradian succession within the ‘chlorite’ Barrovian metamorphic zone (Barrow zones include chlorite-biotite-garnet-staurolite-kyanite-sillimanite).

In thin section, the microtexture is dominated by muscovite and quartz grains formed during low grade metamorphism and compositional bands that reflect the original sedimentary layering. The bands were deformed and crenulated by later folding and deformation. If you look carefully you'll that the thin section contains the nose of a small fold picked out by the boundary between the compositional bands. Later fluids and associated iron staining penetrated along the crenulation cleavage.

Additional images
  • Phyllite
  • phyllite
Map
55.023333, -7.821111
Precision:
Moderate
About this collection

The United Kingdom Virtual Microscope (UKVM) collection consists of igneous, sedimentary and metamorphic rocks from around the UK.

It is intended as a teaching resource, helping to tell the story of the common rock types and how they form, and reflecting the history of the UK at the margins of the continent of Europe. The collection is a series of teaching sets, for example igneous rocks from the North Atlantic Igneous Province and SW England; high-temperature metamorphic rocks from Scotland and low-temperature metamorphic rocks from Wales; and sedimentary rocks, including English limestones and sandstones.

Sample details

Type
metamorphic
Category
phyllite
Rock-forming mineral
muscovite
quartz
Category guide  
Category Guide
Title
Refers to any word or phrase that appears in the individual rock names. Names are generally descriptive; they allow users to search for broad terms like ‘granite’ as well as more specific names such as ‘breccia’. However, the adjacent descriptions of the specimens captures a wider range of general words and phrases and is a more powerful search tool.
Description
Refers to any word or phrase that appears anywhere in the descriptions of the specimens
Accessory minerals
Minerals that occur in very low abundance in a rock. They are usually not visible with the naked eye and contribute perhapssver, they often dominate the rare elements such as platinum group metals.
Rock-forming minerals
Minerals that make up the bulk of all rock samples and are also the ones used in rock classi?cation.
Timescale
Selecting one or more period, for example 'Jurassic'.
Theme
A term used to group together related samples that are not already gathered into a single Collection. For instance, there is a ‘SW England granites’ theme that includes such rock types as granite, hydrothermal breccia, skarn and vein samples.
Category
A general term used to label a rock sample. It is a useful way of grouping similar samples throughout a collection. Category names are often, but not exclusively, common rock names (e.g. granite, basalt, dolerite, gabbro, greisen, skarn, gneiss, amphibolite, limestone, sandstone).
Owner
The owner of the sample that appears in the collection. For example, NASA owns all the samples that appear in the Moon Rocks collection
We would like to thank the following for the use of this sample: