What is granulite in geology?
Granulites are a class of high-grade metamorphic rocks of the granulite facies that have experienced high-temperature and moderate-pressure metamorphism. They are of particular interest to geologists because many granulites represent samples of the deep continental crust.
What facies is gneiss?
The granulite facies consists of very high grade metamorphic rocks like gneiss.
What is the Protolith of granulite?
The petrochemical as well as zircon U-Pb and Lu-Hf isotopic studies of granulite facies metamorphic rock from the Taoxi Group in eastern Nanling Range, Central Cathaysia indicate that its protolith is the sedimentary rock with low maturation index.
What metamorphic facies is schist?
The greenschist facies consists of a group of rocks that contain green platy minerals like chlorite and epidote. Chlorite schist is an ideal example of the rocks within this facies. The amphibolite facies comprises relatively high metamorphic rocks like biotite schist and amphibole schist.
What is the cleavage of sillimanite?
| Sillimanite | |
|---|---|
| Color | Colourless or white to grey, also brown, yellow, yellow-green, grey-green, blue-green, blue; colourless in thin section |
| Crystal habit | Prismatic crystals, fibrous, acicular |
| Cleavage | {010} perfect |
| Fracture | Splintery |
Which is the best definition of an isograd?
In geology, an isograd is a plane of constant metamorphic grade in the field; it separates metamorphic zones of different metamorphic index minerals.
How are isograds used to describe metamorphic rocks?
In metamorphic rock: Isograds Reactions that introduce new minerals in rocks of a specific bulk composition are referred to as mineral appearance isograds. Isograds can be mapped in the field as lines across which the metamorphic mineral assemblage changes. Caution must be exercised to note the approximate bulk…. Read More.
Where did the concept of facies come from?
The facies concept was developed by Eskola in 1939. Recall that the names of Eskola’s facies are based on mineral assemblages found in metabasic basic rocks. Applying the facies concept to the Dalradian series of Scotland, one finds only two facies represented.
Is the isograd distribution associated with nappe structures normal?
Isograd distributions associated with nappe structures can be either normal or inverted, depending on the relative rates of nappe emplacement and heat transfer.