Search results
Results From The WOW.Com Content Network
Amphibolite from Cape Cod, Massachusetts Garnet bearing amphibolite from Val di Fleres, Italy. Amphibolite (/ æ m ˈ f ɪ b ə l aɪ t /) is a metamorphic rock that contains amphibole, especially hornblende and actinolite, as well as plagioclase feldspar, but with little or no quartz.
The amphibolite facies is a facies of medium pressure and average to high temperature. It is named after amphiboles that form under such circumstances. It has the following mineral assemblages: In metabasites: hornblende + plagioclase ± epidote, garnet, cummingtonite, diopside, biotite; In metapelites:
Gore Mountain Garnet, found in the Adirondack Mountains in New York, contains the world's largest garnets. [1] [2] The rock that holds these garnets, garnet amphibolite, is sometimes referred to as 'black ore' or 'dark ore.' [1] [3] This rock formation formed during metamorphism during the Ottawan phase of the Grenvillian orogeny, and extremely high temperatures combined with introduction of ...
The facies are named after the metamorphic rock formed under those facies conditions from basalt. [79] The particular mineral assemblage is somewhat dependent on the composition of that protolith, so that (for example) the amphibolite facies of a marble will not be identical with the amphibolite facies of a pellite.
[4] [5] [6] A semipelite is defined in part as having similar chemical composition but being of a crystalloblastic nature. [7] Pettijohn (1975) [8] gives the following descriptive terms based on grain size, avoiding the use of terms such as clay or argillaceous which carry an implication of chemical composition. The Ancient Greek terms are more ...
Banded iron formations, sedimentary rock that formed in sea water; Garnet in "faux-amphibolite", Nuvvuagittuq Greenstone Belt. The cummingtonite amphibolite that dominates the belt is unusual that sections of the rock have a grayish-beige color, compared to the dark green of common amphibolites, giving it the nickname "faux-amphibolite".
Blastomylonites are coarse grained, often sugary in appearance without distinct tectonic banding.; Ultramylonites usually have undergone extreme grainsize reduction. In structural geology, ultramylonite is a kind of mylonite defined by modal percentage of matrix grains [clarify] more than 90%. [4]
The pressures exceed those of greenschist, blueschist, amphibolite or granulite facies. Eclogites containing lawsonite (a hydrous calcium-aluminium silicate) are rarely exposed at Earth's surface, although they are predicted from experiments and thermal models to form during normal subduction of oceanic crust at depths between about 45–300 km ...