What is the protolith of amphibolite?
Amphibolite is a metamorphosed mafic igneous rock (basalt, gabbro) although it is usually difficult to determine the protolith because original features are often obliterated. Basalt is composed of pyroxene + plagioclase. Schistose rocks with a similar composition are hornblende schists.
What is the protolith of eclogite?
Eclogite contains no plagioclase although its protolith is full of this mineral. The protoliths of eclogites are igneous rocks with a basaltic composition (basalt, diabase, gabbro). The lack of relatively light-weight plagioclase is the reason why it is so dense compared to its protoliths.
What is the parent rock of amphibolite?
Mafic igneous rocks (e.g., basalts and gabbros) and sedimentary dolomite can be the parent rocks of amphibolite.
What is the grain size of eclogite?
Phengite and ilmenite are rarely present. Omphacite occurs as aligned elongated crystals that impart a strong compositional layering and a penetrative lineation to the eclogite. Garnets occur as small subidioblastic grains, usually 0.3 mm in size; larger grains (up to ∼0.6 mm) are rare.
Where is amphibolite most commonly found?
Amphiboles are found principally in metamorphic and igneous rocks. They occur in many metamorphic rocks, especially those derived from mafic igneous rocks (those containing dark-coloured ferromagnesian minerals) and siliceous dolomites.
What is amphibolite good for?
Amphibolite has a variety of uses in the construction industry. It is harder than limestone and heavier than granite. These properties make it desirable for certain uses. Amphibolite is quarried and crushed for use as an aggregate in highway construction and as a ballast stone in railroad construction.
What is the importance of eclogite rocks?
Eclogite ( /ˈɛklədʒaɪt/) is a metamorphic rock formed when mafic igneous rock is subjected to high pressure. Eclogite forms at pressures greater than those typical of the crust of the Earth. An unusually dense rock, eclogite can play an important role in driving convection within the solid Earth.
How is eclogite formed?
Eclogites consist primarily of green pyroxene (omphacite) and red garnet (pyrope), with small amounts of various other stable minerals—e.g., rutile. They are formed when volcanic or metamorphic rocks rich in such mafic minerals are subjected to extremely high pressures and moderate to relatively high temperatures.
Is amphibolite a schist?
Amphibolite is a grouping of rocks composed mainly of amphibole and plagioclase feldspar, with little or no quartz. Tremolite, while it is a metamorphic amphibole, is derived most usually from highly metamorphosed ultramafic rocks, and thus tremolite-talc schist is not generally considered as ‘amphibolite’.
What is the importance of eclogite?
What grade of metamorphism is amphibolite?
Amphibolite facies, one of the major divisions of the mineral-facies classification of metamorphic rocks, the rocks of which formed under conditions of moderate to high temperatures (500° C, or about 950° F, maximum) and pressures.
Does amphibole have 1 cleavage plane?
In chemical composition and general characteristics they are similar to the pyroxenes. Most apparent, in hand specimens, is that amphiboles form oblique cleavage planes (at around 120 degrees), whereas pyroxenes have cleavage angles of approximately 90 degrees.
Which is the protolith of an eclogite rock?
The protoliths of eclogites are igneous rocks with a basaltic composition (basalt, diabase, gabbro ). The lack of relatively light-weight plagioclase is the reason why it is so dense compared to its protoliths. The formation of eclogite may be expressed by the following chemical equation:
What happens when Amphibolite is replaced with eclogite?
At higher temperature, amphibolite and granulite are directly replaced by eclogite (lines 5 and 6, in Figure 5 ). The transition from blueschist to eclogite facies (line 7, in Figure 5) is a very gradual boundary.
Which is the metamorphic form of eclogite 5?
Eclogite. Where sedimentary rocks have been metamorphosed under eclogite facies conditions, schist or gneiss forms instead of eclogite 5. Hence, not all eclogite facies rocks are eclogites, nor are all eclogites formed under the conditions of eclogite facies (some eclogites formed at the conditions of amphibolite or blueschist facies).
Where do amphibolite facies and granulite facies occur?
High-grade metamorphics (predominantly amphibolite facies, eclogite-facies basic rocks and rare granulite facies rocks preserved as relicts) occur, usually as cores within Phanerozoic fold structures.