Metamorphic Rocks Practice exam questions written by Timothy H. Heaton, Professor of Earth Sciences, University of South Dakota. Click the circle by an answer with the mouse, then click on the Submit button to get a response. You will be told if your answer is correct or not and will be given some comments.
The relatively low-pressure metamorphism of greenstone rocks is comparable to seafloor metamorphism in which rocks undergo low-grade metamorphism between 300 and 500 C at low to intermediate.Barrovian metamorphism is the most commonly encountered type of metaorphism. It occurs in intense tectonic conditions associated with. low grade (greenschist facies) middle grade (amphibolite facies) high grade (granulite facies) These three facies are named after the three kinds of rocks, Greenschist, Amphibolite, and granulite. If we observe a terrane of increasing metamorphic intensity.Within a given metamor phic area, the terms lower and higher grade have been used to indicate the relative intensity of metamorphism, as related to either increasing temperature or increasing pressure conditions of metamorphism or often both.
Metamorphism, mineralogical and structural adjustments of solid rocks to physical and chemical conditions differing from those under which the rocks originally formed. Changes produced by surface conditions such as compaction are usually excluded. The most important agents of metamorphism include temperature, pressure, and fluids.
Metamorphism is the solid state recrystallisation of minerals. Both rocks are metamorphosed by regional metamorphism (directed pressure), however schist is metamorphosed more than slate. Therefore.
A special type of metamorphism takes place under these very high-pressure but relatively low-temperature conditions, producing an amphibole mineral known as glaucophane (Na 2 (Mg 3 Al 2)Si 8 O 22 (OH) 2), which is blue in colour, and is a major component of a rock known as blueschist.
Metamorphic rocks. Metamorphism is the alteration of pre-existing rocks in the solid state due to changes in temperature and pressure.. This mineral will crystallise if the rock is subjected to high pressure and temperature. A granular texture is characteristic of some metamorphic rocks. Note: As the grade of metamorphism increases (more temperature and pressure), both crystal size and the.
Slate is produced by low grade metamorphism, which is caused by relatively low temperatures and pressures. Slate has been used by man in a variety of ways over the years. One use for slate was in the making of headstones or grave markers. Slate is not very hard and can be engraved easily. The problem with slate though is its perfect cleavage. The slate headstones would crack and split along.
The intensity of metamorphism and the vigor of metamorphic transformation are expressed by the term metamorphic grade. If, for instance, a granitic pluton intrudes a pile of sediments, the resulting contact metamorphic aureole will contain rocks of higher grade close to the contact of the pluton (heat source) and rocks of low grade at greater distance from the pluton where the sediments were.
Slate refers to a fine-grained, low-grade metasedimentary rock in which bedding is typically still visible: Schist refers to a medium- to high-grade, medium- to coarse-grained metamorphic rock of any composition that has a fabric. For example, Gneiss refers to a high-grade, coarse-grained metamorphic rock of any composition that has a fabric.
The best known and most commonly seen metamorphic rocks are those produced by Barrovian (also called regional) metamorphism. Beginning with a shale parent, Barrovian metamorphism produces a sequence of metamorphic rocks that goes through slate, and then through phyllite, schist, and gneiss. It can be hard to imagine at first that all these very different looking rocks can come from the same.
The high grade metamorphism refers to the metamorphism that takes place at temperatures that are greater than 320 degree Celsius. The high grade metamorphism also takes place at relatively high.
Retrograde metamorphism is normally produced by repeated regional metamorphism where a lower grade episode is superimposed on a higher grade one. Most retrogressive events are probably just a consequence of the metamorphic system cooling down after peak metamorphism has been reached (i.e. the system has to cool down with time and as the region undergoes uplift with time, both pressure and.
A metamorphic facies is a set of mineral assemblages in metamorphic rocks formed under similar pressures and temperatures. The assemblage is typical of what is formed in conditions corresponding to an area on the two dimensional graph of temperature vs. pressure (See diagram in Figure 1). Rocks which contain certain minerals can therefore be linked to certain tectonic settings, times and.
Why LOW GRADE HIGH GRADE LOW GRADE HIGH GRADE Contact metamorphism generally from GEO 102 at Stony Brook University.
A second difference from slate rock is the grade of metamorphism in schist. Recall that slate rock is considered a low-grade metamorphic rock. With schist rock, because of the higher temperature.
As discussed previously, contact metamorphism occurs as a result of a high geothermal gradient produced locally around intruding magma. Contact metamorphism is usually restricted to relatively shallow depths (low pressure) in the Earth because it is only at shallow depths where there will be a large contrast in temperature between the intruding magma and the surrounding country rock.