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METAMORPHIC ROCKS
Lesson 1 - Page 6

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In regional metamorphism conditions can range from low to high pressures and temperatures that occur over a large area. This will produce different zones or rocks that have characteristic minerals. The minerals are like a pressure gauge and thermometer and record the history of the conditions under which the rocks formed.

Finding these minerals in metamorphic rocks are clues to the temperature and pressure. For example, chlorite, muscovite, and biotite (all micas) are common in low grade metamorphism which is low temperatures (200EC) and pressure. (Remember water boils at 100EC). Intermediate grade metamorphisms usually contains the minerals garnet and staurolite. High grade metamorphism (800EC) usually produces kyanite and sillimanite


A. Kyanite, B. Sillimanite

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