What type of metamorphic facies are associated with subduction of oceanic crust?

Asked By: Elois Huidobro | Last Updated: 29th June, 2020
Category: science geology
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Subduction zone metamorphism is characterized by a low temperature, high-ultrahigh pressure metamorphic path through the zeolite, prehnite-pumpellyite, blueschist, and eclogite facies stability zones of subducted oceanic crust.

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In this regard, what is ocean floor metamorphism?

Ocean-floor metamorphism is a concept that has arisen from recent studies of present oceanic ridges and fracture zones where new crust is being generated, altered, and deformed.

Additionally, what are 2 metamorphic minerals formed along oceanic ridges? Ocean-ridge metamorphism This metamorphism is attributed to the high heat flow and intense fluid circulation that occurs along oceanic ridges. Resulting metamorphic rocks usually include greenstones and amphibolites, i.e., the low- and medium-grade metamorphic equivalents of oceanic basalt.

Beside above, how are Isograds related to metamorphic facies?

Isograds are lines drawn to connect the first observed occurrence of an index mineral, such as garnet, when traveling from low-grade to high-grade metamorphic rocks. Geologists can, therefore, "contour" the ancient distributions of metamorphic temperatures and pressures in a terrain by mapping isograds.

What type of plate boundary is metamorphism most common?

Contact metamorphism is common at both convergent and divergent plate boundaries, in areas where molten rock is produced. Regional metamorphism largely occurs at convergent plate boundaries. Each of these types of metamorphism produces typical metamorphic rocks, but they may occur in different sequences.

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What is thermal metamorphism?

Definition of thermal metamorphism. A type of metamorphism resulting in chemical reconstitution controlled by a temperature increase, and influenced to a lesser extent by confining pressure; there is no requirement of simultaneous deformation.

What type of metamorphism occurs at low temperature and high pressure?

Hydrothermal metamorphism occurs when hot, chemically active, mineral laden waters interact with a surrounding preexisting rock (called the country rock). Most hydrothermal metamorphism takes place at low pressures and relatively low temperature, as the phase diagram shows.

Where does dynamic metamorphism occur?

Dynamic metamorphism is associated with zones of high to moderate strain such as fault zones. Cataclasis, crushing and grinding of rocks into angular fragments, occurs in dynamic metamorphic zones, giving cataclastic texture.

Where does burial metamorphism occur?

Burial metamorphism occurs to rocks buried beneath sediments to depths that exceed the conditions in which sedimentary rocks form. Because rocks undergoing burial metamorphism encounter the uniform stress of lithostatic pressure, not differential pressure, they do not develop foliation.

What does pelitic mean?


Definition of pelitic. i. Pertaining to or characteristic of pelite; esp. said of a sedimentary rock composed of clay, such as a pelitic tuff representing a consolidated volcanic ash consisting of clay-size particles.

What does the nature of metamorphic facies depend on?

The mineral assemblages that occur in metamorphic rocks depend on four factors: The bulk chemical composition of the original rock. The pressure reached during metamorphism. The temperature reached during metamorphism.

How Migmatite is formed?

Migmatites form under extreme temperature and pressure conditions during prograde metamorphism, when partial melting occurs in metamorphic paleosome. Components exsolved by partial melting are called neosome (meaning 'new rock'), which may or may not be heterogeneous at the microscopic to macroscopic scale.

Why do we use metamorphic facies?

The concept of metamorphic facies is a systematic way to look at the mineral assemblages in rocks and determine a potential range of pressure and temperature (P/T) conditions that were present when they formed.

What is a Metabasite?

Definition of metabasite. A collective term, first used by Finnish geologists, for metamorphosed mafic rock that has lost all traces of its original texture and mineralogy owing to complete recrystallization.

What is the barrovian sequence?


Barrovian-type metamorphism. In pelites, Barrovian-type metamorphism is marked by the development of a sequence of index minerals, starting with chlorite in the lowest-grade rocks, and passing upgrade through biotite, garnet, and kyanite, to sillimanite in the highest-grade rocks (see BARROW'S ZONES).

What are the textures of metamorphic rocks?

TEXTURES Textures of metamorphic rocks fall into two broad groups, FOLIATED and NON-FOLIATED. Foliation is produced in a rock by the parallel alignment of platy minerals (e.g., muscovite, biotite, chlorite), needle-like minerals (e.g., hornblende), or tabular minerals (e.g., feldspars).

Where does Metasomatism occur?

Metasomatism takes place in some rocks adjacent to igneous intrusions (see Contact (thermal) metamorphism; Skarn). It may also affect extensive areas (regional metasomatism), with the introduction of fluids possibly related to partial fusion at depth.

What controls the degree of metamorphism?

The main factors that control metamorphic processes are:
The temperature at which metamorphism takes place. The amount and type (direction) of pressure during metamorphism. The amount and type of fluid (mostly water) that is present during metamorphism. The amount of time available for metamorphism.

How deep is the oceanic crust?

The oceanic crust
It is typically 7 km thick, though often less along the crest of mid-ocean ridges. Oceanic crust is formed as a result of decompression melting in the mantle at relatively shallow depths below the mid-ocean ridges, as the mantle rises in passive response to plate separation.

How thick is the oceanic crust?


The oceanic crust is 5 km (3 mi) to 10 km (6 mi) thick and is composed primarily of basalt, diabase, and gabbro. The continental crust is typically from 30 km (20 mi) to 50 km (30 mi) thick, and it is mostly composed of less dense rocks than is the oceanic crust.

What are the characteristics of the oceanic crust?

What are the characteristics of oceanic crust? Oceanic crust is thinner and more dense than continental crust. This is because it has been compressed by the weight of the oceans it carries above it. It is also much younger than Continental crust, as it is usually less than 200 million years old.

What elements make up the oceanic crust?

Oceanic crust is primarily composed of mafic rocks, or sima, which is rich in iron and magnesium.