What is eclogite parent rock?
Table of Contents
What is eclogite parent rock?
eclogite, any member of a small group of igneous and metamorphic rocks whose composition is similar to that of basalt. Eclogites consist primarily of green pyroxene (omphacite) and red garnet (pyrope), with small amounts of various other stable minerals—e.g., rutile.
What is the significance of eclogites at Earth’s surface?
The eclogites are very helpful in clarifying the patterns and processes of plate tectonics, as it represents the crustal rocks that were subducted to depths over 35 km, and then returned to the Earth’s surface.
What do Blueschist facies indicate?
The blueschist metamorphic facies are characterized by the minerals jadeite, glaucophane, epidote, lawsonite, and garnet. They record metamorphism in the cool high-pressure/low-temperature thermal gradients at less than 7°C/km in subduction zones in the last 1 billion years.
What type of metamorphic rock is eclogite?
Eclogite ( /ˈɛklədʒaɪt/) is a metamorphic rock containing garnet (almandine-pyrope) hosted in a matrix of sodium-rich pyroxene (omphacite). Accessory minerals include kyanite, rutile, quartz, lawsonite, coesite, amphibole, phengite, paragonite, zoisite, dolomite, corundum, and, rarely, diamond.
What grade is eclogite facies?
high-grade metamorphism
Amphibolite facies: medium-grade metamorphism. Granulite facies: high-grade metamorphism. Blueschist facies: low-temperature/high-pressure metamorphism. Eclogite facies: high-grade metamorphism.
What is blueschist used for?
In Minoan Crete blueschist and greenschist were used to pave streets and courtyards between 1650 and 1600 BC. These rocks were likely quarried in Agia Pelagia on the north coast of central Crete.
What environment produces the blueschist facies?
Metamorphism under very high pressures and relatively low temperatures, such as occurs along subduction zones, constitutes the Blueschist Facies because basalt and shale metamorphosed under these conditions often contain blue amphiboles called glaucophane.
Is eclogite high metamorphic grade?
Eclogite: A high P/T metamorphic rock composed of more than 75% vol. garnet (often pyrope or Mg-rich almandine) and omphacite (Na-Ca-Al-Mg clinopyroxene). Both must be present and neither component more than 75% vol.
How do you identify amphibolite?
Long prismatic, acicular, or fibrous crystal habit, Mohs hardness between 5 and 6, and two directions of cleavage intersecting at approximately 56° and 124° generally suffice to identify amphiboles in hand specimens. The specific gravity values of amphiboles range from about 2.9 to 3.6.
How are amphibolite facies formed?
Amphibolite frequently forms by metamorphism of mafic igneous rocks, such as basalt. However, because metamorphism creates minerals entirely based upon the chemistry of the protolith, certain ‘dirty marls’ and volcanic sediments may also metamorphose to an amphibolite assemblage.
What texture is amphibolite?
Amphibolite
| Type | Metamorphic Rock |
|---|---|
| Texture | Non-foliated to weakly-foliated; Medium-grained |
| Composition | Amphibole and Plagioclase |
| Index Minerals | Amphibole |
| Color | Black |
What characteristics is a metaconglomerate?
Metaconglomerate is a rock type which originated from conglomerate after undergoing metamorphism. Conglomerate is easily identifiable by the pebbles or larger clasts in a matrix of sand, silt, or clay. Metaconglomerate looks similar to conglomerate, although sometimes the clasts are deformed.
Why is blueschist so rare?
Blueschist is rare, since the conditions that produce it are rather odd. It’s also rarely very old, as it’s easily changed by further metamorphic events. So, if you get a chance to see this most beautiful rock in person, appreciate it for the treasure it is.
What are the characteristics of eclogite facies?
Eclogite facies is characterized by pressures in excess of 1.2 GPa (45 km depth) and temperature exceeding at least 400-500 °C. 400-500 degrees at 45 km depth is below the crustal average (25 °C per kilometer of depth).
How many types of eclogite are there?
The chemistry of primary and accessory minerals is used to classify three types of eclogite (A, B, and C). The broad range of eclogitic compositions has led a longstanding debate on the origin of eclogite xenoliths as subducted, altered oceanic crust .
Where did the eclogite come from?
Eclogite occurs as tectonic inclusions in metasedimentary rocks at several locations within the Yukon Territory. Evidence from the Ross River (RR) eclogite suggests greater depths of burial than previously considered.
What is a facies model?
The Geological Association of Canada (now Geoscience Canada) in 1976 introduced the iconic series Facies Models, edited by Roger Walker. This set of papers, perhaps more than any others, brought facies models into the mindful living rooms of students of sedimentology and stratigraphy. The volume has been reprinted and re-edited several times since.
