A mafic-hornfels containing plagioclase and hornblende.
What minerals does hornfels contain?
7.4. They consist of andalusite, garnet, and cordierite as major minerals and quartz, feldspar, biotite, muscovite, and pyroxene as a characteristic mineral. Hornfels often include epidote, diopside, actinolite, or wollastonite and sometimes Titanite, and tremolite.
What type of rock is hornfels?
Hornfels is a metamorphic rock formed by the contact between mudstone / shale, or other clay-rich rock, and a hot igneous body, and represents a heat-altered equivalent of the original rock. This process is termed contact metamorphism.
What does the presence of hornfels reveal?
It reveals that the rock has undergone metamorphism at a shallow depth and have been transformed due to heating by igneous masses through contact metamorphism.
What metamorphic rocks contain calcite?
Marble is a common metamorphic rock which is mostly composed of calcite.
How are hornfels made?
All of the rocks called hornfels—a hard, fine-grained, flinty rock—are created when heat and fluids from the igneous intrusion alter the surrounding rock, changing its original mineralogy to one that is stable under high temperatures.
Where are hornfels found?
In Africa, hornfels is found in Tanzania, Cameroon, East Africa, and Western Africa. The rock is found in Australia and New Zealand, as well.
Can Hornfels be foliated?
Hornfels. Hornfels is another non-foliated metamorphic rock that normally forms during contact metamorphism of fine-grained rocks like mudstone or volcanic rocks.
Are Hornfels smooth?
Other features: Generally smooth to touch. Parent Rocks and Protoliths: Hornfels is not a rock that is “deposited”. Instead it is a rock type that forms when an existing rock is metamorphosed.
What caused hornfels quartzites and marble to change from their parent rocks?
The heat generated by the magma chamber has changed these sedimentary rocks into the metamorphic rocks marble, quartzite, an hornfels. Regional Metamorphism occurs over a much larger area. Regional metamorphism is caused by large geologic processes such as mountain-building.
Why are hornfels fine-grained?
Hornfels is a fine-grained metamorphic rock that was subjected to the heat of contact metamorphism at a shallow depth. It was “baked” by heat conducted from a nearby magma chamber, sill, dike, or lava flow. This specimen of hornfels is thought to have formed with sandstones and siltstones as the protoliths.
Is plagioclase a silicate or non silicate?
Plagioclase is a member of the feldspar group (like orthoclase) and is a framework silicate. Plagioclase consists of a solid solution between the albite and anorthite end-members, and together with quartz is the most common of the rock forming minerals.
What rock forms quartzite?
Quartzite is a metamorphic rock derived from sandstone that is distinguished from sandstone by its fracture. Sandstone breaks along grain boundaries, whereas quartzite is so well indurated (hardened) that it breaks across constituent grains.
Is shale a sedimentary rock?
Common sedimentary rocks include sandstone, limestone, and shale. These rocks often start as sediments carried in rivers and deposited in lakes and oceans. When buried, the sediments lose water and become cemented to form rock.