Ophiolite
Topic: Minerals, Rocks and the Rock Cycle · NCERT: Beyond NCERT
Meaning
An ophiolite is a slice of old ocean crust and upper mantle that has been pushed up onto land. This happens where two plates collide and the ocean between them closes. Ophiolites mark a suture, the line where two landmasses joined. They are made of dark, iron- and magnesium-rich rocks, so they can hold chromite and nickel.
Example
Ophiolites run along the Indus–Tsangpo suture in Ladakh, where the Indian plate met the Eurasian plate. They also occur in the Naga–Manipur hills, which have chromite and nickel, and on the Andaman Islands.
Don't confuse with
- Ocean-floor basalt: ordinary ocean crust stays under the sea and sinks back into the mantle at trenches. An ophiolite is a piece of that crust that has been lifted onto a continent.