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Metamorphic Rocks. How do metamorphic rocks form?. When high temperature and pressure combine to alter the texture, mineralogy, or chemical composition of a rock without melting it, metamorphic rock forms. Metamorphism is separated into grades.
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How do metamorphic rocks form? • When high temperature and pressure combine to alter the texture, mineralogy, or chemical composition of a rock without melting it, metamorphic rock forms.
When molten rocks come into contact with solid rock, a local effect called CONTACT METAMORPHISM may result.
Minerals that crystallize at the hottest temperatures are found closest to the intrusion. Other minerals are found in bands surrounding the intrusion.
When very hot water reacts with rock and alters its chemistry and mineralogy, _________ metamorphism occurs.
Classification of Metamorphic Rocks • Foliated • Wavy layers and bands of minerals • High Pressure during metamorphism causes minerals with flat or needle-like crystals to form with long axes perpendicular to the pressure. • Examples: schist (from shale); gneiss (from granite)
Classification of Metamorphic Rocks 2. Non-foliated Lack mineral grains with long axes in one direction. Made primarily of minerals that form with blocky crystal shapes instead (like puzzle pieces) Ex: quartzite (from sandstone); marble (from limestone)
