The learning point of this earthcache is to be able to identify and recognize Migmatite.
At the location you will find a metamorphic rock, a type of rock that has undergone a high degree of **metamorphism. Migmatite is part of a large group of medium- to coarse-grained metamorphic rocks with a banded structure, formed by regional metamorphism. The composition is often granitic to granodioritic, often with darker layers. If you look closely at the stone, you will see several minerals playing out that make up the whole of the stone. But the most famous minerals are feldspar and quartz. The crystals will play well with their colours, and the stone has its main colour for a reason. You will become more familiar with the stone and its structure by studying it well and going through the cache description. Good luck.
**Metamorphism is a process that changes preexisting rocks into new forms because of increases in temperature, pressure, and chemically active fluids. Metamorphism may affect igneous, sedimentary, or other metamorphic rocks.
Migmatite:
Migmatite is a rock formed by partial melting of an earlier rock. It consists of a mixture of molten rock ( neosome , usually lighter in colour), and the rest of the original rock.
Migmatite forms at high temperatures above the melting point, and characterizes deeper parts of mountain ranges. "True" migmatites are formed by local melting, but there are also migmatites that are formed by injection of melt formed elsewhere in the crust. The crystals are typical medium size/coarse-grained, which means that the crystals in the stone were formed deep down in the earth's crust. The larger the crystals are, the deeper down they are made by a long periode of time, with alot of pressure and heat.
Migmatites show various patterns of light and dark bands or sheaths, often with folded granitic layers. The amount of melt (leucosome) can vary greatly, depending on how strongly melted the original rock is, and how much melt has left the migmatite. In general, light minerals have a lower melting point than dark ones. The high temperatures during the metamorphosis have caused the light minerals in the rock to melt earlier than the dark ones that thus float around the molten mass. They are broken up and create twisted, layered shapes and folds.
Migmatites are a source of magma and igneous rocks, and define the transition between metamorphic and igneous rocks. As mentioned, Migmatite means mixed rock and is thus a metamorphic rock. Migmatite is a subtype of gneiss. Migmatite consists of a large group of medium- to coarse-grained metamorphic rocks with a banded structure, formed by regional metamorphism. The composition is often granitic to granodioritic, often with dark and light layers.
The boundary between metamorphism and magmatism is not obvious, since by definition metamorphism groups all physical and chemical transformations that occur in rocks in the solid state, that is, from solid to liquid state, while magmatism is interested in the latter. from liquid state to solid state. We therefore identify here a problem linked to strict sensory definition of these scientific fields.
Migmatites are rocks that in a pressure-temperature diagram lie between solidus and liquidus. They can belong to the domain of metamorphism or magmatism depending on the intensity of the partial fusion (that is, the intensity of the metamorphism) that they have undergone. The physical barrier given to this limit is the Arzi threshold, a threshold experimentally obtained for a liquid/solid ratio of 12 to 20%.
To log this cache.
To get to log this cache you will have to visit and answer the questions which are related to the coordinates given the earthcache.
When answers are collected, send them to CO for verification.
You can log immediately after answers are sent CO. If there are any questions about your answers CO will contact you.
Logs without answers to CO or with pending questions from CO will be deleted without any further notice.
Please do not include pictures in your log that may answer the questions.
Questions:
1. Answer the questions under by visiting the Coordinates.
A. Study the rock at the location, what characteristic features can you see, and what colours do we have in the stone? Look carefully!
B. Now you are going to study the crystals in the stone, what size are they, and is the stone fine, medium or coarse-grained? The size of the crystal will tell whether the stone was formed high up or deep down in the earth's crust, describe this based on the crystal size from GZ.
C. Would you say this is a mixed stone or just a one-kind stone? Is there a mineral structure/folds of light and/or dark mass? Would that indicate that it had a high or low melting point during its formation?
2. Take a photo of you, the group or the GPS from the location without revealing any of the answers.
