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Metamorphic Rocks. Metamorphic Rocks. Metamorphism is the changes in a rock that result in the formation of metamorphic mineral assemblage. Metamorphic rocks may have foliation in response to temperature and/or pressure, application of differential stress, and hydrothermal fluids.
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Metamorphic Rocks • Metamorphism is the changes in a rock that result in the formation of metamorphic mineral assemblage. • Metamorphic rocks may have foliation in response to temperature and/or pressure, application of differential stress, and hydrothermal fluids.
Metamorphic Rocks • Metamorphism involves phase changes, recrystallization, neocrystallization, pressure solution, and/or plastic deformation. • Hot water can also bring in and remove elements.
Metamorphic Rocks • Foliation is the alignment of crystals or the mineral orientation. It often has compositional banding. • Occurs where differential stress causes the compression and shearing of a rock. Inequant crystals align parallel to one another.
Metamorphic Rocks • Classes of metamorphic rocks include foliated and non-foliated rocks. • Class depends upon foliation.
Metamorphic Rocks • Foliated rocks include: slate, phyllitemetaconglomerate, schist, and gneiss. • Non-foliated rocks include: hornfels, quartzite, and marble. • Migamite is a mixture of igneous and metamorphic rock.
Metamorphic Rocks • Low-grade rocks are those that form under relatively low temperatures. • High-grade rocks form under high temperatures. • Intermediate rocks form between the two extremes.
Metamorphic Rocks • Index minerals are used to track the distribution of different grades of rocks. • Points where index minerals first appear are called isograds. • A metamorphic zone exists between two isograds.
Metamorphic Rocks • Metamorphic facies is a group of metamorphic mineral assemblages. • They develop under a specified range of temperature and pressure conditions.
Metamorphic Rocks • Contact metamorphism occurs in an aureole surrounding an igneous intrusion. • Burial metamorphism occurs at depth in a sedimentary basin. • Dynamically metemorphosed rocks form along faults and often undergo plastic shearing. • Hydrothermal metamorphism is caused by circulation of hot water. • Shock metamorphism is from an impact of a meteorite.
Metamorphic Rocks • Metamorphic rocks can be found in mountain ranges. • Blueschist forms in accretionary prisms. • Precambrian metamorphic rocks can give way to shields.
