Students can be introduced to the links between metamorphism and plate tectonics by evaluating how plates behave sequentially from where they form through to where they are subducted
. As oceanic crust is formed, saline ocean water circulates deeply through the basalt and gabbro forming in the hot environment of the mid-ocean ridges (divergent boundaries).
It is produced by dynamo thermal metamorphism and metasomatism, which occur in the zones where tectonic plates are subducted
, changing rocks by heat and pressure, with influx of fluids but without melting.
Based on mineralogy and textures, eclogites are interpreted to be deeply subducted
rocks due to India-Kohistan collision followed by rapid exhumation resulting from the Himalayan uplift.
As the continent accelerated the amount of sediment being subducted
decreased and India slowed before finally colliding with Asia.
The presence of boron in the blue diamonds suggests that at least that element was able to hitch a ride with the subducted
oceanic plates into the deep mantle, Smith said.
The research suggests that formation of adakite has various reasons including partial melting of subducted
oceanic crust, crystallization differentiation of mantle-derived basaltic magma, migmatization of magma, partial melting of delaminated lower crust and partial melting of thickened lower crust.
Scientists have seismic evidence that the deep part of the mantle is a graveyard where long ago slabs of earth were subducted
, or thrust underneath one another, creating separate regions with different chemical compositions that eventually made their way to the surface in a hot mantle plume, or upwelling, as the core heated the rock into magma.
The undersea megathrust earthquake was caused when the Indian Plate was subducted
by the Burma Plate and triggered a series of devastating tsunamis along the coasts of most landmasses bordering the Indian Ocean, killing 230,000 people in 14 countries, and inundating coastal communities with waves up to 30 metres (100 ft) high It was one of the deadliest natural disasters in recorded history.
"Some models suggest the presence of two subduction zones; with the Indian plate being subducted
beneath the Hindu Kush region and the Eurasian plate being subducted
beneath the Pamir region.
The strongest activity is centered at an intermediate depth of 60-200 km due to an old subducted
tectonic plate which can currently be found in an almost vertical position.