Granite intrusion
In geology, an igneous intrusion (or intrusive body or simply intrusion) is a body of intrusive igneous rock that forms by crystallization of magma slowly cooling below the surface of the Earth. Intrusions have a wide variety of forms and compositions,
Because the solid country rock into which magma intrudes is an excellent insulator, cooling of the magma is extremely slow, and intrusive igneous rock is coarse-grained (phaneritic). Intrusive igneous rocks are classified separately from extrusive igneous rocks, generally based on their mineral content. The relative amounts of quartz, alkali feldspar, plagioclase, and feldspathoid is particularly important in classifying intrusive igneous rocks.
Intrusions must displace existing country rock to make room for themselves. The question of how this takes place is called the room problem, and it remains a subject of active investigation for many kinds of intrusions.
Intrusions are broadly divided into discordant intrusions, which cut across the existing structure of the country rock, and concordant intrusions that intrude parallel to existing bedding or fabric. These are further classified according to such criteria as size, evident mode of origin, or whether they are tabular in shape.
An intrusive suite is a group of intrusions related in time and space.
Different types of Discordant intrusions include:
Dikes
Ring dikes and cone sheets
Volcanic necks
Diatremes and breccia pipes
Stocks
Batholiths
Different types of Concordant intrusions include:
Sills
Laccoliths
Lopoliths and layered intrusions
The room problem
Pluton emplacement
The ultimate source of magma is partial melting of rock in the upper mantle and lower crust. This produces magma that is less dense than its source rock. For example, a granitic magma, which is high in silica, has a density of 2.4 Mg/m3, much less than the 2.8 Mg/m3 of high-grade metamorphic rock. This gives the magma tremendous buoyancy, so that ascent of the magma is inevitable once enough magma has accumulated. However, the question of precisely how large quantities of magma can shove aside country rock to make room for themselves (the room problem) is still a matter of research.
The composition of the magma and country rock and the stresses affecting the country rock strongly influence the kinds of intrusions that take place. For example, where the crust is undergoing extension, magma can easily rise into tensional fractures in the upper crust to form dikes. Where the crust is under compression, magma at shallow depth will tend to form laccoliths instead, with the magma penetrating the least competent beds, such as shale beds. Ring dikes and cone sheets form only at shallow depth, where a plug of overlying country rock can be raised or lowered. The immense volumes of magma involved in batholiths can force their way upwards only when the magma is highly silicic and buoyant, and are likely do so as diapirs in the ductile deep crust and through a variety of other mechanisms in the brittle upper crust.
To log as found please send me the answers to the following:
1 - The dominate color of the granite intrusion at PZ.
2 - The average width of the granite intrusion at PZ
3 - As an option a picture of you or your GPS at PZ would be appreciated. 
Pour vous inscrire comme trouvé, veuillez m'envoyer les réponses aux questions suivantes :
1 - La couleur dominante de l'intrusion de granite au PZ.
2 - La largeur moyenne de l'intrusion de granite à PZ.
3 - En option une photo de vous ou de votre GPS au PZ serait appréciée.