Metamorphic Rock Formation and Garnet

What mineral indicates that a metamorphic rock was formed at a great depth under extreme heat and pressure?

a) Feldspar b) Mica c) Garnet d) Quartz

Final answer: The mineral Garnet indicates that a metamorphic rock was formed at a great depth under extreme heat and pressure, through a process known as plate tectonics.

Answer

The mineral Garnet indicates that a metamorphic rock was formed at a great depth under extreme heat and pressure, through a process known as plate tectonics.

In the identification of metamorphic rock formation and the depth of its occurrence, the presence of certain minerals is paramount. Notably, garnet is a key indicator. Metamorphic rocks are created under high temperature and pressure conditions, deep within the Earth's crust. The geological process is known as plate tectonics.

Using the example of quartzite, we can understand this process better. Firstly, a primitive material undergoes heat treatment in the nascent Earth to form igneous rock. Over time, this igneous rock undergoes chemical transformations and redepositing, eventually turning into sedimentary rock. When this sedimentary rock is subjected to extreme heat and pressure several kilometers below the Earth's surface, it changes into a hard, white metamorphic stone like quartzite.

However, the identification of garnet in the rock's matrix reveals its high-grade metamorphic nature. The presence of garnet indicates the rock was formed under extreme conditions, providing a testament to the intense metamorphosis it underwent deep within the Earth's crust.