What is metamorphic facies give example?
What is metamorphic facies give example?
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).
What metamorphic facies is quartzite?
Quartzite is a nonfoliated metamorphic rock composed almost entirely of quartz. It forms when a quartz-rich sandstone is altered by the heat, pressure, and chemical activity of metamorphism.
What type of metamorphism is associated with amphibolite facies?
Basic rocks metamorphosed to the amphibolite facies are amphibolites, containing mostly hornblende and plagioclase. Basic rocks metamorphosed to the eclogite facies are eclogites, containing the green sodic pyroxene called omphacite and garnet.
Which mineral is commonly present in Sanidinite facies?
Amphibole, diopside, epidote, plagioclase, almandine and grossular garnet, and wollastonite are minerals typically found in rocks of the amphibolite facies.
What are the different types of metamorphic facies?
Types Of Metamorphic Facies
- Hornfels facies: low- to high-grade metamorphism.
- Zeolite facies: low-grade metamorphism.
- Greenschist facies: low-grade metamorphism.
- Amphibolite facies: medium-grade metamorphism.
- Granulite facies: high-grade metamorphism.
- Blueschist facies: low-temperature/high-pressure metamorphism.
What are the characteristics of metamorphic facies?
In current usage, a metamorphic facies is a set of metamorphic mineral assemblages, repeatedly associated in space and time, such that there is a constant and therefore predictable relation between mineral composition and chemical composition. The facies concept is more or less observation-based.
Is quartzite worth anything?
Quartz’s clarity earns it a raw price of around $0.01/carat and a gem price of $1-$7/carat. Amethyst, or purple quartz, is the most valuable variety (can reach $15/carat), but pink, rose, and smokey quartz is also valuable. Clearer, more vibrant, and unbroken specimens are the most valuable quartz.
What is the toughest rock?
Diamond
Diamond is the hardest known mineral, Mohs’ 10.
Is amphibolite a schist?
Melanocratic, fine- to coarse-grained, weakly to strongly foliated, irregularly layered amphibole-rich gneiss and schist….Amphibolite, Amphibole Gneiss, and Schist.
| State | Virginia |
|---|---|
| Name | Amphibolite, Amphibole Gneiss, and Schist |
| Geologic age | Proterozoic Y |
What are the three most important kinds of metamorphism?
Three types of metamorphism exist: contact, dynamic, and regional. Metamorphism produced with increasing pressure and temperature conditions is known as prograde metamorphism. Conversely, decreasing temperatures and pressure characterize retrograde metamorphism.
What is ACF diagram?
ACF diagram A three-component, triangular graph used to show how metamorphic mineral assemblages vary as a function of rock composition within one metamorphic facies. The minerals quartz and albite are assumed to be present in the rocks and are not shown on the diagram.
What two variables are used to define metamorphic facies?
One of the two variables, temperature and pressure, is very high and the other moderate to very high. The presence of water is important in the genesis of these rocks, since rocks that are originally anhydrous may recrystallize in these facies at lower temperatures and pressures than are otherwise required.
What makes a metamorphic facies different from other facies?
Carbonate rocks have a different composition than a basalt lava, the minerals that can grow in them are different too. Therefore, a meta psammite and a meta pelite will have different mineralogical compositions even though they are in the same metamorphic facies. Every metamorphic facies has some index minerals by which it can be recognized.
What are the abbreviations for metamorphic facies of rocks?
Apart from the metamorphic facies of a rock, a whole terrane can be described by the abbreviations LT, MT, HT, LP, MP, HP (from low, medium or high; pressure or temperature). Since the 1980s the term UHP (ultra high pressure) has been used for rocks that experienced extreme pressures.
What happens to the mineral assemblage during metamorphism?
In general, the mineral assemblage preserved in a metamorphic rock is frozen at the highest temperature experienced during metamorphism ( see above Retrograde metamorphism ), and thus the facies and facies series to which the rock would be assigned reflect only a single point on its P-T-t path.
Which is the metamorphic facies with the highest temperature?
In K 2 O-poor sediments or meta-igneous rocks: The pyroxene-hornfels facies is the contact-metamorphic facies with the highest temperatures and is, like the granulite facies, characterized by the mineral orthopyroxene. It is characterized by the following mineral assemblages: