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:
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.
Examples include sillimanite, kyanite, staurolite, andalusite, and some garnet. [15] Other minerals, such as olivines, pyroxenes, hornblende, micas, feldspars, and quartz, may be found in metamorphic rocks but are not necessarily the result of the process of metamorphism. These minerals can also form during the crystallization of igneous rocks ...
A shield is a large area of exposed Precambrian crystalline igneous and high-grade metamorphic rocks that form tectonically stable areas. [1] These rocks are older than 570 million years and sometimes date back to around 2 to 3.5 billion years.
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 fragments then formed Bennu and other "rubble pile" asteroids - loose amalgamations of rocky material rather than solid objects. Early in its history, some of the ice inside the parent body ...
The metasediments and metavolcanics formed first, followed by granites more than 2.7 billion years ago. The rock record contains an uncertain age gap with younger 1.8 billion years old Proterozoic quartzofeldspathic and migmatite gneiss, with amphibolite and biotite schist .