There are two main types of metamorphic rocks: those that are foliated This is illustrated in Figure , where the parent rock is shale, with bedding as shown. . When it forms, the calcite crystals tend to grow larger, and any sedimentary. In regional metamorphism the source of increased temperature and pressure What is the relationship between metamorphic foliation and sedimentary bedding ? sedimentary bedding and metamorphic foliation are two terms for the same. Explain the relationship among slate, phyllite, schist and gneiss in terms of . Metamorphic rock textures are foliated, non-foliated, or lineated are described below. The thin layers in slate may resemble sedimentary bedding, but they are a.
Thermal metamorphism in the aureole of a granite is also unlikely to result in growth of mica in a foliation, although growth of new minerals may overprint existing foliation s.
Alignment of tabular minerals in metamorphic rocksigneous rocks and intrusive rocks may form a foliation. Typical examples of metamorphic rocks include porphyroblastic schists where large, oblate minerals form an alignment either due to growth or rotation in the groundmass. Igneous rocks can become foliated by alignment of cumulate crystals during convection in large magma chambersespecially ultramafic intrusions, and typically plagioclase laths.
Granite may form foliation due to frictional drag on viscous magma by the wall rocks. Lavas may preserve a flow foliation, or even compressed eutaxitic texture, typically in highly viscous felsic agglomeratewelded tuff and pyroclastic surge deposits.
Metamorphic differentiation, typical of gneissesis caused by chemical and compositional banding within the metamorphic rock mass.
Usually this represents the protolith chemistry, which forms distinct mineral assemblages. However, compositional banding can be the result of nucleation processes which cause chemical and mineralogical differentiation into bands. This typically follows the same principle as mica growth, perpendicular to the principal stress.
Difference Between Foliation and Layering | Difference Between | Foliation vs Layering
Metamorphic differentiation can be present at angles to protolith compositional banding. Interpretation[ edit ] Foliation, as it forms generally perpendicular to the direction of principal stress, records the direction of shortening. This is related to the axis of folds, which generally form an 'axial-planar' foliation within their axial regions. Measurement of the intersection between a fold's axial plane and a surface on the fold will provide the fold plunge. If a foliation does not match the observed plunge of a fold, it is likely associated with a different deformation event.
- Difference Between Foliation and Layering
- What is the relation between metamorphic foliation and sedimentary bedding?
Foliation in areas of shearing, and within the plane of thrust faultscan provide information on the transport direction or sense of movement on the thrust or shear. They can record how long-term tectonic processes shape our planet.
Rock cycle showing the five materials such as igneous rocks and sediment and the processes by which one changes into another such as weathering. The changes in composition and texture occur without melting the rock. In general, the chemistry of the protolith can be changed by heat, a type of pressure called confining pressure, and fluids.
While the texture is changed by a type of pressure called directed stress.
6 Metamorphic Rocks
The following sections will discuss each metamorphic process in more detail. This may be the heat of a body of igneous rock trapped within a volcano, or the heat of ocean water. On the other hand, temperature is the measure of the vibrational kinetic energy of a substance. Therefore, as the temperature of a body increases, the vibrational energy rises.
At the atomic scale, high temperatures cause atoms in the crystal structure to vibrate so vigorously that the atoms can jump from one position to another in the crystal. So, temperature can affect the chemical makeup of minerals in a rock by affecting the chemical equilibrium, or balance of cations in minerals.
Since temperature increases with increasing depth with the Earth geothermal gradientmetamorphic rocks are affected by depth and these rocks can record these temperature changes within their minerals.
Metamorphic rocks lie in between sedimentary rocks and magma in the rock cycle diagram above.
However, the temperature at which a mineral melts is dependent on the pressure. Pressure Pressure is the force exerted over a unit area on a material. Like heat, pressure can affect the chemical equilibrium. The pressure that affects metamorphic rocks can be grouped into confining pressure and directed stress. Strain is the result of this stress, including metamorphic changes within minerals.
Confining Pressure Difference between pressure and stress and how they deform rocks. Under directed stress, some stress directions forces are stronger than others, and this can deform rocks.
When pressure is exerted from rocks above, it is balanced from below and sides, and is called confining or lithostatic pressure. These chemical reactions will cause new minerals to form. Confining pressure is measured in bars and ranges from 1 bar at sea level to around 10, bars at the base of the crust.
Directed Stress Pebbles in quartzite deformed by directed stress Directed stress, or differential or tectonic stress, is an unequal balance of forces on a rock in one or more directions see figure above. In contrast to confining pressure that cause chemical reactions, the magnitudes of directed stress are much lower and do not cause chemical reactions to occur. Directed stresses are ultimately caused by the physical motion of large-scale plates of lithosphere.
Most importantly, while minerals are being mechanically manipulated, they are not melted, and do not need to change chemically or compositionally at all. Just the arrangement of crystals.