Notice the sequence of rocks that from, beginning with slate higher up where pressures and temperatures are lower, and ending in migmatite at the bottom where temperatures are so high that some of the minerals start to melt. It is composed primarily of quartz. A hard rock that is easy to carve, marble is often used to make floor tiles, columns and sculptures. Supplying quality educational materials for teachers, collectors and other educational organizations since 1995. That means it will take a long time to heat up, can be several hundreds of degrees cooler than the surrounding mantle. This is not always the case, however. Introduction to Hydrology and Glaciers, 13a. Quartzite: Formed by the metamorphism of pure quartz sandstone. It is foliated, crenulated, and fine-grained with a sparkly appearance. Quartzite is composed of quartz sand grains. The specimen shown above is about two inches (five centimeters) across. Contact metamorphic aureoles are typically quite small, from just a few centimeters around small dykes and sills, to as much as 100 m around a large stock. Metaconglomerate looks similar to conglomerate, although sometimes the clasts are deformed. Geologic unit mapped in Maryland: Silvery-gray, well foliated, micaceous quartz-pebble metaconglomerate and quartzite; apparent maximum thickness 700 feet. Foliated textures show four types of foliation. The Himalaya range is an example of where regional metamorphism is happening because two continents are colliding (Figure 6.25). This is distinct from cleavage in minerals because mineral cleavage happens between atoms within a mineral, but rock cleavage happens between minerals. As already noted, slate is formed from the low-grade metamorphism of shale, and has microscopic clay and mica crystals that have grown perpendicular to the stress. If a rock is both heated and squeezed during metamorphism, and the temperature change is enough for new minerals to form from existing ones, the new minerals can be forced to grow longer perpendicular to the direction of squeezing (Figure 10.7). This means that the minerals in the rock are all aligned with each other. . Q. Slaty cleavage, schistosity, and compositional banding are all examples of ______. Fractional crystallization is the opposite of partial melting. . What are some of the differences between foliated rocks and nonfoliated rocks? Even though the quartz crystals themselves are not aligned, the mass of quartz crystals forms a lens that does follow the general trend of alignment within the rock. In the example shown in Figure 7.8d, the dark bands are largely amphibole while the light-coloured bands are feldspar and quartz. The specimen shown above is about two inches (five centimeters) across. The Origin of Earth and the Solar System, Chapter 8. Anthracite coal is similar to bituminous coal. Seeing and handling the rocks will help you understand their composition and texture much better than reading about them on a website or in a book. 2023 Leaf Group Ltd. / Leaf Group Media, All Rights Reserved. Foliated textures show a distinct planar character. Some examples of foliated rocks include. It is foliated, crenulated, and fine-grained with a sparkly appearance. Los Angeles Community College District: What Is a Foliated Metamorphic Rock? Image copyright iStockPhoto / RobertKacpura. Adding foil creates a layer, so foliated rocks are layered rocks. The effects of recrystallization in Figure 10.9 would not be visible with the unaided eye, but when larger crystals or large clasts are involved, the effects can be visible as shadows or wings around crystals and clasts. Conglomerate is easily identifiable by the pebbles or larger clasts in a matrix of sand, silt, or clay. Dynamic metamorphism occurs at relatively low temperatures compared to other types of metamorphism, and consists predominantly of the physical changes that happen to a rock experiencing shear stress. The aligned minerals are mostly mica, which has a platy crystal habit, with plates stacked together like pages in a book. This means that the minerals in the rock are all aligned with each other. In some cases, hornfels has visible crystals of minerals like biotite or andalusite. Jurassic metaconglomerate bij Los Peasquitos Canyon Preserve , San Diego County, Californi . Houston, TX: Lunar and Planetary Institute Read full text, Physical Geology, First University of Saskatchewan Edition by Karla Panchuk is licensed under CC BY-NC-SA 4.0 Adaptation: Renumbering, Remixing, https://openpress.usask.ca/physicalgeology/. Gneiss is a foliated metamorphic rock that has a banded appearance and is made up of granular mineral grains. It typically contains abundant quartz or feldspar minerals. EARTH SCIENCE LAB Metamorphic Sample #1: Identify the Texture, Foliation, Composition, Parent Rock and Rock Type Metamorphic Rock Identification Chart FOLIATION COMPOSITION PARENT ROCK ROCK NAME TEXTURE Oslaty O mica Mudstone O phyllitic O quartz, mica, chlorite O Mudstone O Foliated Omica, quartz O Slate O schistose amphibole, plagioclase O In sheared zones, however, planar fabric within a rock may not be directly perpendicular to the principal stress direction due to rotation, mass transport, and shortening. Amphibolite is a non-foliated metamorphic rock that forms through recrystallization under conditions of high viscosity and directed pressure. The pebbles have developed "wings" to varying degrees (e.g., white dashed ellipse). As already noted, slate is formed from the low-grade metamorphism of shale, and has microscopic clay and mica crystals that have grown perpendicular to the stress. As metamorphic processes go, burial metamorphism takes place at relatively low temperatures (up to ~300 C) and pressures (100s of m depth). Minerals can deform when they are squeezed (Figure 10.6), becoming narrower in one direction and longer in another. lineation - a parallel arrangement of pebbles in a metaconglomerate foliation - a segregation of felsic and mafic minerals into alternating layers as in gneiss. The kinds of rocks that can be expected to form at different metamorphic grades from various parent rocks are listed in Table 7.1. The protolith for slate is shale, and sometimes fossils that were present in the original rock can be seen in freshly sheared layers of slate. However, a more complete name of each particular type of foliated metamorphic rock includes the main minerals that the rock comprises, such as biotite-garnet schist rather than just schist. The mineral alignment in the metamorphic rock called slate is what causes it to break into flat pieces (Figure 10.12, left), and is why slate has been used as a roofing material (Figure 10.12, right). Platy minerals tend to dominate. If you happen to be in the market for stone countertops and are concerned about getting a natural product, it is best to ask lots of questions. Schist is a metamorphic rock with well-developed foliation. There are two major types of structure - foliation and (non-foliated) massive. Examples of foliated rocks include: gneiss, phyllite, schist, and slate. Most foliation develops when new minerals are forced to grow perpendicular to the direction of greatest stress. answer choices. Igneous rocks can become foliated by alignment of cumulate crystals during convection in large magma chambers, especially ultramafic intrusions, and typically plagioclase laths. Marble is made of dolomite or calcite, and they result from the metamorphism of limestone or dolostone. The grains form a mosaic texture. This forms planes of weakness, and when these rocks break, they tend to break along surfaces that parallel the orientation of the aligned minerals (Figure 10.11). A fine-grained rock that splits into wavy sheets. Foliated metamorphic rocks exhibit layers or stripes caused by the elongation and alignment of minerals in the rock as it undergoes metamorphism. Thermal metamorphism in the aureole of a granite is also unlikely to result in the growth of mica in a foliation, although the growth of new minerals may overprint existing foliation(s). A special type of metamorphism takes place under these very high-pressure but relatively low-temperature conditions, producing an amphibole mineral known as glaucophane (Na2(Mg3Al2)Si8O22(OH)2). Metamorphic rocks are rocks that have undergone a change from their original form due to changes in temperature, pressure or chemical alteration. In most cases, this is because they are not buried deeply, and the heat for the metamorphism comes from a body of magma that has moved into the upper part of the crust. Water within the crust is forced to rise in the area close to the source of volcanic heat, drawing in more water from further away. Metaconglomerate, however, breaks through the grains, as the cement has recrystallized and may be as durable as the clasts. Dynamic metamorphism is the result of very high shear stress, such as occurs along fault zones. The high pressures are to be expected, given the force of collision between tectonic plates, and the increasing lithostatic pressure as the subducting slab is forced deeper and deeper into the mantle. The protolith for quartzite is quartz, and because quartz is stable under high pressure and high temperatures, metamorphism of this rock simply causes the reorganization of its crystals. In geology, key terms related to metamorphic rocks include foliated and nonfoliated. Anthracite is the highest rank of coal. The sudden change associated with shock metamorphism makes it very different from other types of metamorphism that can develop over hundreds of millions of years, starting and stopping as tectonic conditions change. In the formation of schist, the temperature has been hot enough so that individual mica crystals are visible, and other mineral crystals, such as quartz, feldspar, or garnet may also be visible. University of Notre Dame: Prograde Metamorphism. Drag the appropriate labels to their respective targets. Territories. Shocked quartz (Figure 6.32 left) refers to quartz crystals that display damage in the form of parallel lines throughout a crystal. Essentially, the minerals are randomly oriented. Introduction to Hydrology and Groundwater, 12a. On the other hand, any clay present in the original sandstone is likely to be converted to mica during metamorphism, and any such mica is likely to align with the directional pressure. Hornfels is another non-foliated metamorphic rock that normally forms during contact metamorphism of fine-grained rocks like mudstone or volcanic rock (Figure 7.13). Typically, these rocks split along parallel, planar surfaces. Slaty cleavage is composed of platy minerals that are too small to see. It is composed of alternating bands of dark and light minerals. Foliated metamorphic rocks exhibit layers or stripes caused by the elongation and alignment of minerals in the rock as it undergoes metamorphism. 1. Want to create or adapt OER like this? Slate exhibits slaty foliation, which is also called cleavage. Metamorphic rock may exhibit a variety of features related to the organization and arrangement of its component materials. Chlorite and serpentine are both hydrated minerals, containing water in the form of OH in their crystal structures.

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