How do metamorphic rocks form at subduction zones?
Subduction zones host a unique variety of rock types created by the high-pressure, low-temperature conditions a subducting slab encounters during its descent. The metamorphic conditions the slab passes through in this process creates and destroys water bearing (hydrous) mineral phases, releasing water into the mantle.
Which metamorphic facies is associated with subduction zones?
High-Pressure Metamorphism Blueschist-facies metamorphism is important in subduction zones, where high-pressure, relatively low-temperature mineral assemblages form. Glaucophane and lawsonite, both of which have a bluish color, are common minerals in this setting.
What is formed through plate subduction?
Deep trenches are features often formed where tectonic plates are being subducted and earthquakes are common. As the sinking plate moves deeper into the mantle, fluids are released from the rock causing the overlying mantle to partially melt.
What happens at a subduction plate boundary?
Where two tectonic plates meet at a subduction zone, one bends and slides underneath the other, curving down into the mantle. (The mantle is the hotter layer under the crust.) At a subduction zone, the oceanic crust usually sinks into the mantle beneath lighter continental crust.
What happens to rock around a subducting plate?
The rock around a subduction plate or subducting zone passes under the other plate at the boundary and is heated to melting due to friction between the plates. This melted rock returns to the mantle where it becomes part of the convective flow of liquid rock/magma in the mantle.
Does metamorphism occur in subduction zones?
With respect to metamorphism, the most important feature of subduction zones is their low heat flow. Some metamorphism occurs in material that has been accreted to the base of the overlying plate; 3. The high-pressure rocks are incorporated into the upper plate by a shift in the location of the Benioff zone.
Is eclogite a metamorphic facies?
The protoliths of eclogites are igneous rocks with a basaltic composition (basalt, diabase, gabbro). It is a rock type that gave name to a metamorphic facies. Eclogite facies is characterized by pressures in excess of 1.2 GPa (45 km depth) and temperature exceeding at least 400-500 °C.
Is greenschist a metamorphic facies?
greenschist facies, one of the major divisions of the mineral facies classification of metamorphic rocks, the rocks of which formed under the lowest temperature and pressure conditions usually produced by regional metamorphism.
How subduction can cause volcanism?
Thick layers of sediment may accumulate in the trench, and these and the subducting plate rocks contain water that subduction transports to depth, which at higher temperatures and pressures enables melting to occur and ‘magmas’ to form. The hot buoyant magma rises up to the surface, forming chains of volcanoes.
Which plate boundary is formed between the Philippine plate and the Eurasian plate?
subduction zone
The Nankai Trough subduction zone is a typical subduction system characterized by subduction of multiple geological units of the Philippine Sea Plate (the Kyushu-Palau Ridge, the Shikoku Basin, the Kinan Seamount Chain, and the Izu-Bonin Arc) beneath the Eurasian Plate in the southwest of Japan.
How does subduction cause landmass formation?
When the other plate is forced down the process is called subduction. The plate enters into the magma and eventually it is completely melted. That is how the surface of the earth makes way for the crust created over time at other plate boundaries. These pockets of magma find paths to the surface and create volcanoes.
What causes the subduction of the Philippine plate?
The Philippine Fault is a left-lateral strike-slip fault which cuts across the Philippine archipelago behind the subduction zone. It is an NW-SE trending fault, which aligns subparallel to the Philippine Trench, extends from northern Luzon to Mindanao.
What are the characteristics of subduction zone metamorphism?
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.
What are the mineral assemblages of metamorphic facies?
Definitive Mineral Assemblages of Metamorphic Facies Mineral assemblages in mafic rocks of the facies of contact meta- morphism do not differ substantially from that of the corresponding regional facies at higher pressure. 2
What is the high-P/T type metamorphic facies series?
The high-P/T type metamorphic facies series shows a progressive change from Prehnite-Pumpellyite facies through blueschist facies to eclogite facies across the orogenic belt, representing a low geothermal gradient caused by a cooling effect due to continuous subduction of cold oceanic crust and sediments.
What is the relationship between plate tectonics and metamorphism?
Metamorphism and Plate Tectonics. Metamorphic rocks result from the forces active during plate tectonic processes. The collision of plates, subduction, and the sliding of plates along transform faults create differential stress, friction, shearing, compressive stress, folding, faulting, and increased heat flow.