greenschist


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greenschist

[′grēn‚shist]
(petrology)
A schistose metamorphic rock with abundant chlorite, epidote, or actinolite present, giving it a green color.
References in periodicals archive ?
All these units are metamorphosed to greenschist grade in contrast to the surrounding gneissic rocks.
Field examination, microscopic study, and X-ray analysis indicate that the rocks have been metamorphosed to the chlorite grade of the greenschist facies.
The second one shows the greenschist facies, represented by chlorite + actinolite + epidotes + quartz (Figure 3d).
Strata in the Britannia Pendant have been folded, faulted and altered by regional greenschist facies metamorphism and local contact metamorphism.
It contains terrigenous sedimentary rocks, mafic to ultramafic volcanic rocks and plutonic rocks metamorphosed from the greenschist facies to the lower amphibolite facies.
Although Raeside and Barr (1990, 1992) interpreted the gneissic rocks of the northern outcrop areas of the Barachois River suite as being correlative with lower grade phyllite and greenschist in the southern Cape Breton Highlands and with metasiltstone in the Big Hill and Kellys Mountain areas, that relationship is uncertain.
These rocks have all been metamorphosed to greenschist facies and most are intensely foliated.
Retrograde greenschist facies minerals indicate a Palo-Proterozoic to possibly Meso-Proterozoic age for this large scale faulting, which has been favourable for other economic uranium deposits within the Precambrian Shield in the Uranium City area of north-central Saskatchewan.
Given the absence of biotite, the metamorphic grade of this area could not have been higher than lower greenschist facies, and peak temperatures occurred during the formation of [S.
Many features of this group are not obviously different than the features of the first group; for example, host rocks are affected by greenschist metamorphism, gold-beating arsenopyrite is present, and formation temperatures above 400[degrees]C are reported for some of the largest deposits.
The stratigraphic sequence is a biotite-rich turbidite metamorphosed to upper greenschist facies.
Metamorphic grade generally does not exceed greenschist facies, and in many places, primary sedimentary and igneous textures are well preserved.