Which type of rock is rich in magnesium and iron, found in new oceanic crust?

The type of rock that is rich in magnesium and iron and is found in new oceanic crust is basalt. Basalt is a mafic igneous rock that forms from the rapid cooling of lava at the Earth's surface, particularly at mid-ocean ridges where new oceanic crust is created. Its high iron and magnesium content gives basalt its characteristic dark color and density.

In the context of plate tectonics, the formation of new oceanic crust through volcanic activity at mid-ocean ridges primarily produces basalt. This process is essential for the continual renewal of the ocean floor and contributes to the geological cycle of the Earth.

The other types of rocks listed are not primarily associated with the composition of oceanic crust. Granite, for example, is a felsic rock that is lighter in color and composition, typically found in continental crust. Sandstone is a sedimentary rock composed mainly of sand-sized mineral particles, and limestone is a sedimentary rock primarily made of calcium carbonate, formed from biological sources. These rocks do not share the magnesium and iron-rich characteristics that define basalt.